# To use gearbox & adapter plate - or not ?



## Richard500 (Mar 12, 2021)

Hi all,

I'm a serious newbie, and am embarking on my first ev conversion (of a very tired old Triumph Spitfire) here in the UK. Can anyone explain to me in simple terms why most conversions keep the gearbox and use an adapter plate to bolt on the electric motor ?
I get that it's probably simpler for alignment etc., but also extra weight and a bit redundant given the torque of an electric motor ? ... my gearbox is pretty shot & I would prefer to do without it altogether and just connect the electric motor to the propshaft ... is this a really dumb thing to do, or is it a sensible proposition ?

P.S. Apologies if this has been answered many times before, but I couldn't find an answer through the search.
Many thanks,
R


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## dedlast (Aug 17, 2013)

I don't think anyone is ignoring you, it just feels that way sometimes. The short answer is it depends on what motor you are going to use. Usually, the motor needs more reduction than the final drive can provide. For example, the Nissan Leaf has a final drive ratio (actually, the only ratio) of 8.19:1, depending on the model year. Meanwhile the Spitfire has anywhere from 3.27:1 to 4.11:1. So, slower RPM, less efficiency, and less torque at the wheels. That's just one variable that goes into that decision. And, unfortunately, all I have time for today.

B


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## Electric Land Cruiser (Dec 30, 2020)

The reason is because of RPM like dedlast has said. I also want to direct drive my vehicle and ditch the transmission, but I need a 2:1 or 3:1 reduction in between to make it work. Think of it like this: the average internal combustion engine revs to 5000 or 6000 rpm, the average electric motor revs to 8000 or 100000rpm. That means to get the same wheel speed, the electric motor needs to reduce the output RPM by half, or have a Triumph Spitfire that has the potential to go 200mph (but never will).

If I were you I would look into changing the rear differential ratio to a taller ratio or to use a nissan leaf type transaxle in the rear of the Spitfire to maintain good RPM/MPH ratio.


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## brian_ (Feb 7, 2017)

Electric Land Cruiser said:


> The reason is because of RPM like dedlast has said. I also want to direct drive my vehicle and ditch the transmission, but I need a 2:1 or 3:1 reduction in between to make it work. Think of it like this: the average internal combustion engine revs to 5000 or 6000 rpm, the average electric motor revs to 8000 or 100000rpm. That means to get the same wheel speed, the electric motor needs to reduce the output RPM by half, or have a Triumph Spitfire that has the potential to go 200mph (but never will).


Right... and that's why using the original transmission and leaving it in second gear would work for a motor with that speed range.



Electric Land Cruiser said:


> If I were you I would look into changing the rear differential ratio to a taller ratio or to use a nissan leaf type transaxle in the rear of the Spitfire to maintain good RPM/MPH ratio.


Extreme final drive ratios are not readily available for the Spitfire.
Unfortunately, the Leaf drive unit (motor and transaxle) almost certainly won't fit in the space the Spitfire has in the back.

While keeping the original transmission (or a similar transmission) is one solution to this speed mismatch, another is to use a fixed-ratio (single-speed) gearbox instead. The ev-TorqueBox is an example of this.

For some conversions, the speed range over which the motor can produce enough power is not wide enough, and a multi-speed transmission serves the same purpose as it does with an engine: it is shift to change ratios to keep the motor speed in a suitable range.


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## brian_ (Feb 7, 2017)

dedlast said:


> Usually, the motor needs more reduction than the final drive can provide. For example, the Nissan Leaf has a final drive ratio (actually, the only ratio) of 8.19:1, depending on the model year. Meanwhile the Spitfire has anywhere from 3.27:1 to 4.11:1.


That 8.19:1 is the overall drive ratio. The Leaf - like most EVs - uses a two-stage gear drive, and while only the last stage is literally the "final drive", the ratios for the two stages are generally not provided... only of the overall ratio (of motor speed to axle speed). The final drive ratio of a Leaf is not much different from the Spitfire, but the motor needs the whole 8:1, not just the final drive portion.


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## Duncan (Dec 8, 2008)

The rpm mismatch is a problem if using a modern high revs AC motor

If you use a second hand DC motor from a forklift that problem goes away

If you slightly modify the trans tunnel then you should be able to fit a 9 inch forklift motor where the gearbox normally lives - that will give more than adequate performance and give you the whole engine bay for batteries

I'm using an 11 inch motor - but that would probably tear a spitfire diff apart


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## brian_ (Feb 7, 2017)

Duncan said:


> The rpm mismatch is a problem if using a modern high revs AC motor
> 
> If you use a second hand DC motor from a forklift that problem goes away
> 
> ...


All valid... yet most traditional conversions use brushed DC series-wound motors, keep the transmission, and don't run it in the 1:1 gear at low speed. Only the builders who choose this approach could authoritatively explain why.

NetGain sells the "TransWarP" versions of its "WarP" motors with a transmission tail housing mounted on it to make it easy to use to connect to the driveshaft without a transmission, for people who want to take this approach of using the final drive gearing as the only reduction gearing. This is an easy way to go, but this specific hardware is not required; for instance, Duncan doesn't use this particular motor series.

To match the first-gear acceleration of a stock non-US-market late Spitfire, the motor without additional gearing would need to produce the 111 N-m (82 lbf-ft) of the stock engine multiplied by the 3.50:1 first gear ratio, or 389 N-m (287 lbf-ft). NetGain says that their 9" motor at 500 amps can produce at most 95 N-m (70 lbf-ft). What works for Duncan with an 11" motor and over 300 volts into a 1000 amp controller in a minimal car won't work as well with a 9" motor and typical brushed DC motor voltage into a 500 amp controller in a heavier car.

Among the many Spitfire conversions there are probably multiple cars with 9" brushed DC motors. Even if they have original style transmissions, the drivers of those cars could comment on the performance of the car if driven only in the 1:1 gear (typically the top gear of a 3-speed for 4-speed).


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## Duncan (Dec 8, 2008)

When I was first making my car I intended to use a gearbox
but when I did the calculations I discovered that in top gear I would be able to spin the rear tyres
That made the gearbox a bit unnecessary

When it was first on the road I found that 500 amps was far more than enough to make it fly up the steepest hills 
and lose traction on anything except clean tarmac 
A spitfire is heavier than my car but has less weight on the rear wheels and the rear suspension is not as good

Currently I run 1200 amps - but this is excessively exciting when I have my cheap road tyres fitted - so for road use I have a resister switched into the throttle circuit
This drops me back to 40% - about 500 amps - which is more than enough to make it a fast road car

The voltage is needed to get highway speed - 150 volts and a 9 inch motor is more than enough to maintain 500 amps up to 80 mph 

An 11 inch motor will give more torque - but I am not sure that is a good idea with a spitfire back end


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## Richard500 (Mar 12, 2021)

Gentlemen,
You are stars ! ... this are exactly the kind of issues I have been mulling for a couple of years now, ... but without anyone (who wasn't trying to flog me a £20,000 conversion) to bounce ideas off, I have been struggling a bit. The good thing is I'm now retired, so I have a bit more time to play and figure it all out.

So, if I understand you right, if I'm looking for an AC motor along the lines of a Leaf, I will probably need to keep the gearbox (set at 2nd gear) which gets the AC motor into the 8000 - 10000 rpm range ... in order to get the torque required, or is it just an efficiency thing ?. If I run the Spitfire gearbox in 2nd, then I get an overall ratio (gearbox & final drive) of ~ 8.4 (without gearbox it's 3.9) which gets me into the 10000 rpm range for 80mph that @Electric Land Cruiser , @dedlast and @brian_ mention. Can you guys tell me what voltages & current these motors generally require ?

However, I could opt for DC motor which can run on lower revs and do away with the gearbox as per @Duncan. You,re right, Duncan, that the Spitfire backend is a bit twitchy to say the least, so I am looking for something reasonably tame ... if it gets me to 80mph, get me about town and has a reasonable range then that's as good as it needs to be. I think what you're suggesting is that I need to be looking at running a 9" motor at about 150v and 500amps at top speed. If I have enough battery cells to get me to 40KWh, then am I wrong to think that gives me a range of ~ 45 miles (or is that overly simplistic) ?

A few more follow-on questions spring to mind ...
1. I'm clearly going to have to brush up on my EM motor physics, but why does the AC motor need to rev so high ?
2. Am guessing ebay or gumtree are good places for 2nd hand 9" forklift engines ? ... or are there better places ?
3. Does a forklift engine controller have a CanBus type output to drive a digital speedo (& if not, how do I go about replacing my mechanical speedo currently connected to the gearbox) ?

Many thanks for your responses so far, they've already given me a lot of fuel for thought.
Cheers, R


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## brian_ (Feb 7, 2017)

Just picking out some small items to start...


Richard500 said:


> 1. I'm clearly going to have to brush up on my EM motor physics, but why does the AC motor need to rev so high ?


It doesn't. The power from any motor is the product of the torque and the speed (just multiplied together). The torque capability of a motor is very roughly dependent on the size (mass) of the motor, so it can make sense to use a smaller motor at higher speed (and less torque), to save weight and bulk compared to a heavier motor at lower speed (and higher torque). Since brushless motors *can* run faster (because they don't have brushes to fail or wear out), they provide the _opportunity_ to go faster and therefore smaller.



Richard500 said:


> 2. Am guessing ebay or gumtree are good places for 2nd hand 9" forklift engines ? ... or are there better places ?


They're probably lousy sources; it's likely that the only such motors on eBay are being listed by people who got them for their own projects and are giving up. The frequently shared idea is that you can go to some place that uses electric forklifts, ask nicely, and strip a perfectly good motor out of an old forklift (that has been scrapped for some other reason than battery or motor failure) for next to nothing; while people have done this, it probably is not possible any more in many areas.



Richard500 said:


> 3. Does a forklift engine controller have a CanBus type output to drive a digital speedo (& if not, how do I go about replacing my mechanical speedo currently connected to the gearbox) ?


A DC motor controller doesn't even need to know the speed of the motor, let alone provide it to you on a communications port.
If you keep the gearbox you still have the speedometer drive; if you don't there are electronic speedometers of various designs.


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## zepol_wube (Oct 31, 2015)

I did not see any any of these replies state an alternate option and our eventual plan. We are running a VW golf through the OEM tranny. We were not sure what gear we wanted. We have found 1st to be TOO much fun and now failed. 2nd is great in the city, 3rd for over 55mph. Someday we will drop it all out and either remove R,1,4,5 OR remove R-5 and put in a ~2.8nd single set. In 2nd 0-60 is 6.7 with the motor amps limited to 150 on a Nissan leaf 400V 24kWh pack.
You should be able to shuck out most of the tranny and save in the refit effort of a new solution.


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## dougingraham (Jul 26, 2011)

One thing I haven't seen mentioned by the other posters is that the series wound DC motors have a preferred direction of rotation. You can make them run the other way but it takes at least three contactors to do so. And when running backwards the motor advance timing is not advanced, it is retarded. This causes really rapid brush erosion and wear on the edges of the commutator segments. I kept the transmission in my 85 RX-7 conversion primarily because of the issues with reverse and secondarily to get a closer match to the ideal reduction ratio.

In your spit conversion you will use 2nd gear to take off briskly and probably use third gear most of the time. I normally drive the RX-7 in third gear around town and only shift into 4th on the highway. 

About range. My RX-7 has averaged 204 wh per mile over its life. With a 40 kwh pack this would mean a drop dead range of 196 miles. I have a 16 kwh pack which gives me a 78 mile range. This is with a Warp 9 motor and Soliton controller and the energy measured at the outlet the charger is plugged into. So it includes the losses in the charger.

I recommend buying a salvage Nissan Leaf or Tesla model 3 and taking the parts you need from it and selling the rest rather than buying a series DC motor and controller. You will probably end up with a better conversion this way and it is what I would do if I were going to convert another car.

Best wishes with your conversion!


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## Duncan (Dec 8, 2008)

Richard500 said:


> Gentlemen,
> You are stars ! ... this are exactly the kind of issues I have been mulling for a couple of years now, ... but without anyone (who wasn't trying to flog me a £20,000 conversion) to bounce ideas off, I have been struggling a bit. The good thing is I'm now retired, so I have a bit more time to play and figure it all out.
> 
> So, if I understand you right, if I'm looking for an AC motor along the lines of a Leaf, I will probably need to keep the gearbox (set at 2nd gear) which gets the AC motor into the 8000 - 10000 rpm range ... in order to get the torque required, or is it just an efficiency thing ?. If I run the Spitfire gearbox in 2nd, then I get an overall ratio (gearbox & final drive) of ~ 8.4 (without gearbox it's 3.9) which gets me into the 10000 rpm range for 80mph that @Electric Land Cruiser , @dedlast and @brian_ mention. Can you guys tell me what voltages & current these motors generally require ?
> ...


Re- Forklift motors
DC motors were used until about 2005 - then forklifts went AC - that means that controllers for car use became basically unobtainable
So you need a pre- 2005 motor
They are still about - but as Brian said getting rarer
You need to find the companies that repair forklifts in your area - and go scrounging

I have 14 kwh - and that gives me about 50 km range at 100 kph - with my awful aerodynamics
Speedo
You can buy a nice GPS speedo - if you look you can find a nice retro styled one that does NOT say GPS on the front (they are very accurate but not always "legal"

40 kwh is a lot of batteries - for a small car like a Spitfire you will have difficulty fitting them!


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## macngee (Nov 27, 2014)

I did a lot of research before putting the standard transmission in our Chevy Metro. Most of the posts say there is no need for shifting or using a clutch. A few people say you need to be able to shift the car to make driving enjoyable. The car was originally built with a DC motor coupled to a gutted automatic transmission with around a 3:1 gear ratio. Acceleration from a stop was very uninspiring. I wanted to get the gear ratio down to 6:1 or 8:1. We are currently running an HPEVS AC-51 motor at 120 volts. It is nice to be able to test the car and see the effect of the different gear ratios with the standard transmission. I followed the common route and built the car without a clutch. I will NEVER build another electric car with a transmission without a clutch. To be fair, I race cars and like to drive fast and to shift through the gears. Shifting without a clutch is possible, but it is difficult and slow. The car is an absolute hoot to drive in first gear. When you punch the throttle, it spins the tires and accelerates great. It tops out at about 30MPH in first. Shifting into second gets you to about 55MPH, third tops out around 80MPH, and fourth is good for over 100MPH. Fifth gear is nice for cruising, the lower RPM's make the car quieter and it seems like it's just coasting along. Going up a hill, a lower gear makes the car draw less current so it's more efficient. It's fun just cruising down the road and shifting gears. Especially in an old sports car. I strongly recommend using the standard transmission and a clutch. If you just want to put around and save "fuel" you can get away without a transmission, but if you like torque you will appreciate all of the gears.


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## Duncan (Dec 8, 2008)

macngee said:


> I did a lot of research before putting the standard transmission in our Chevy Metro. Most of the posts say there is no need for shifting or using a clutch. A few people say you need to be able to shift the car to make driving enjoyable. The car was originally built with a DC motor coupled to a gutted automatic transmission with around a 3:1 gear ratio. Acceleration from a stop was very uninspiring. I wanted to get the gear ratio down to 6:1 or 8:1. We are currently running an HPEVS AC-51 motor at 120 volts. It is nice to be able to test the car and see the effect of the different gear ratios with the standard transmission. I followed the common route and built the car without a clutch. I will NEVER build another electric car with a transmission without a clutch. To be fair, I race cars and like to drive fast and to shift through the gears. Shifting without a clutch is possible, but it is difficult and slow. The car is an absolute hoot to drive in first gear. When you punch the throttle, it spins the tires and accelerates great. It tops out at about 30MPH in first. Shifting into second gets you to about 55MPH, third tops out around 80MPH, and fourth is good for over 100MPH. Fifth gear is nice for cruising, the lower RPM's make the car quieter and it seems like it's just coasting along. Going up a hill, a lower gear makes the car draw less current so it's more efficient. It's fun just cruising down the road and shifting gears. Especially in an old sports car. I strongly recommend using the standard transmission and a clutch. If you just want to put around and save "fuel" you can get away without a transmission, but if you like torque you will appreciate all of the gears.


If you use a wimpy motor....
But my Hitachi will spin the tyres and is till accelerating HARD at 96 mph 
So no need for gears or a clutch


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## macngee (Nov 27, 2014)

I hear you, I want to use a Tesla motor for my next conversion. The issue is most of the conversions people are doing would be more fun with a transmission and a clutch.


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## Richard500 (Mar 12, 2021)

brian_ said:


> They're probably lousy sources; it's likely that the only such motors on eBay are being listed by people who got them for their own projects and are giving up. The frequently shared idea is that you can go to some place that uses electric forklifts, ask nicely, and strip a perfectly good motor out of an old forklift (that has been scrapped for some other reason than battery or motor failure) for next to nothing; while people have done this, it probably is not possible any more in many areas.


Thanks Brian, I hadn't thought of that, will do some digging around the local area & see what turns up.


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## Richard500 (Mar 12, 2021)

Duncan said:


> I have 14 kwh - and that gives me about 50 km range at 100 kph - with my awful aerodynamics
> ...
> 40 kwh is a lot of batteries - for a small car like a Spitfire you will have difficulty fitting them!


Thanks, good to know you get 50km from 14kwh (& my aerodymanics probably aren't much better than yours, its actually a morgan-esque kit based on a Spitfire that I built about 35 years ago)
Re 40kwh - yes agreed, hence the desire to lose the gearbox, but I reckon that using the petrol tank space as well, if I need to, I should just about do it.


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## macngee (Nov 27, 2014)

40kWh could probably get you a 100 mile range. I think 20kWh would be plenty, depending on how you are driving.


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## brian_ (Feb 7, 2017)

macngee said:


> I followed the common route and built the car without a clutch. I will NEVER build another electric car with a transmission without a clutch. To be fair, I race cars and like to drive fast and to shift through the gears. Shifting without a clutch is possible, but it is difficult and slow.


It is difficult and slow because the huge rotational inertia of the motor makes the job of the synchronizers much more difficult, especially when shifting down (requiring the input shaft and motor to spin faster). 

The obvious solution is the same as used with an engine and double-declutching: "blip" motor power to bring the input shaft up to the matching speed for the target gear when downshifting (and brake with it to bring the input shaft down for upshifts). Motor controllers don't do this, because production EVs don't shift and aftermarket controllers are not designed as part of a complete powertrain with a transmission. So no one does this, but someone could as a DIY project.

The other non-clutch solution is to use a dog-ring transmission instead of a synchronized transmission... but that would be pretty harsh in a street vehicle. Dog rings would work well in combination with motor control for speed matching, and perhaps a mechanical sequential shifter. I'm not holding my breath waiting for anyone to do this, because it's so much easier to just use a large motor and single-ratio transmission.

At least one electric drag racer used a Lenco transmission, which incorporates cone clutches as shift elements. Lencos are expensive.

The Rimac cars and the Porsche Taycan both have two-speed transmissions (in the rear only), which are shifted by clutches... like a dual-clutch automatic but with only two gear sets and thus no synchros or gear shift mechanism.


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## Duncan (Dec 8, 2008)

Richard500 said:


> Thanks, good to know you get 50km from 14kwh (& my aerodymanics probably aren't much better than yours, its actually a morgan-esque kit based on a Spitfire that I built about 35 years ago)
> Re 40kwh - yes agreed, hence the desire to lose the gearbox, but I reckon that using the petrol tank space as well, if I need to, I should just about do it.


Which "kitcar" is it?
Its not a "Marlin" is it??
I have a Mk2 Marlin Roadster in my shed I'm building just now - but its going to be petrol as I already have a short range electric car and I decided that fitting enough batteries to give me 150 km range was going to be too difficult


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## brian_ (Feb 7, 2017)

Richard500 said:


> ... its actually a morgan-esque kit based on a Spitfire that I built about 35 years ago


In another forum someone noted "In the 80's there were quite a few Morgan lookalike kit cars a lot based on the Herald or Spitfire chassis." As a Spitfire owner, I can't image wanting a Spitfire chassis under another body, but that might have made sense in the UK in the 1980's. 

This is presumably in the style of a Morgan 4/4 or +4. Is it, by any chance, a Burlington SS, Arrow, or Berretta?


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## Richard500 (Mar 12, 2021)

macngee said:


> 40kWh could probably get you a 100 mile range. I think 20kWh would be plenty, depending on how you are driving.


Yes, near there is what I'm aiming at if poss ... gets me to the inlaws and back on one charge (otherwise the driving is just local town stuff & pub lunches etc.).


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## Richard500 (Mar 12, 2021)

Duncan said:


> Which "kitcar" is it?
> Its not a "Marlin" is it??
> I have a Mk2 Marlin Roadster in my shed I'm building just now - but its going to be petrol as I already have a short range electric car and I decided that fitting enough batteries to give me 150 km range was going to be too difficult





brian_ said:


> In another forum someone noted "In the 80's there were quite a few Morgan lookalike kit cars a lot based on the Herald or Spitfire chassis." As a Spitfire owner, I can't image wanting a Spitfire chassis under another body, but that might have made sense in the UK in the 1980's.
> This is presumably in the style of a Morgan 4/4 or +4. Is it, by any chance, a Burlington SS, Arrow, or Berretta?


The Marlins and Burlingtons were nice cars too, but no, its actually a Moss Roadster ... they were around for a short while in the early 1980s & promptly went bust. 
Sorry, I don't have a decent picture on this laptop, but this is the best I've got ...







And yes Brian, I had an old knackerd Vitesse (which was Herald/Spit running gear) and being a student couldn't afford a Morgan, so it made about as much sense as I had at the time 😏. The 2 litre Vitesse engine wouldn't fit so I got an old 1500 Spit & used that ... anyway, I've managed to keep the damn thing for 30+ years with family & kids etc. intervening, so now it's retirement & playtime 🙂.


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## Duncan (Dec 8, 2008)

Richard500 said:


> The Marlins and Burlingtons were nice cars too, but no, its actually a Moss Roadster ... they were around for a short while in the early 1980s & promptly went bust.
> Sorry, I don't have a decent picture on this laptop, but this is the best I've got ...
> View attachment 122122
> And yes Brian, I had an old knackerd Vitesse (which was Herald/Spit running gear) and being a student couldn't afford a Morgan, so it made about as much sense as I had at the time 😏. The 2 litre Vitesse engine wouldn't fit so I got an old 1500 Spit & used that ... anyway, I've managed to keep the damn thing for 30+ years with family & kids etc. intervening, so now it's retirement & playtime 🙂.


Quite similar to the Mk1 Marlin then - fitting 20 kwh of battery will be doable - especially if you use direct drive and fit the motor where the gearbox should live and have the whole engine bay for batteries
IMHO a DC forklift motor is the way to go - a high tech AC motor would be inappropriate!

As far as range is concerned I worked out that I needed under 50km - or over 150 km
My current 14 kwh battery is about 140 kg - three times as much would be difficult to fit and would take the edge off the performance 

20 kwh would be about 210 kg - a 9 inch motor is about 60 kg - so 270 kg - I bet your engine gearbox and the rest of the IC clut would be about the same

For my Marlin 420 kg of batteries would be too much - so I'm fitting a 1300cc ford crossflow


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## HesseJames (Mar 18, 2021)

Good morning Gentlemen,

main reason for me to use clutch and gearbox is to keep original driving experience. OK, it a classic conversion (76 911 Targa), but I want to keep as much from the original as possible. Next reason was to keep an additional safety feature in case everything fails (even main contactor) and motor won't stop spinning. With a clutch you can put it in neutral and no revs to the wheels until you pull your maintanance switch.With keeping your setup that way it is also possible that a newbee to electric cars can drive your car without hassle. But this you don't want to let happen anyway....


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## Richard500 (Mar 12, 2021)

HesseJames said:


> main reason for me to use clutch and gearbox is to keep original driving experience. OK, it a classic conversion (76 911 Targa), but I want to keep as much from the original as possible. Next reason was to keep an additional safety feature in case everything fails (even main contactor)


Yep that's fair, but since my kitcar is a fake by design, I'm not so fussed about originality (in fact, the faker the better if its cool & works). Re safety features, also fair, but I guess I'm good with the off switch (the most likely thing to fail on mine is the clutch pinning it in gear). But if you have a real classic to keep original, then I can see keeping the gearbox would make sense.


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## Richard500 (Mar 12, 2021)

Duncan said:


> Quite similar to the Mk1 Marlin then - fitting 20 kwh of battery will be doable - especially if you use direct drive and fit the motor where the gearbox should live and have the whole engine bay for batteries. IMHO a DC forklift motor is the way to go - a high tech AC motor would be inappropriate!
> As far as range is concerned I worked out that I needed under 50km - or over 150 km
> My current 14 kwh battery is about 140 kg - three times as much would be difficult to fit and would take the edge off the performance
> 20 kwh would be about 210 kg - a 9 inch motor is about 60 kg - so 270 kg - I bet your engine gearbox and the rest of the IC clut would be about the same
> For my Marlin 420 kg of batteries would be too much - so I'm fitting a 1300cc ford crossflow


Re. DC Forklift - yes, I think you're right - I suspect the main challenge is to figure out where to source one from around here - will have to do some thinking.
Re. EV weight vs. IC weight - yes I worked out that they are pretty much on a par if you include a full petrol tank, the EV batteries still come out a bit heavier, but not hugely.

Can you remind me how the voltage/current calcs work ... I think you said you ran yours @ 150v and 500 amps ? ... & what made you choose those values? ... am just checking ('cos its a while since I thought this through), and I think you vary the current to vary the motor speed, and use the highest voltage the motor can take (so as to reduce the current required to get the required power to move the car) ? ... I think ?
Also, what kind of battery is your 14 kwh one ... I was thinking of using Leaf battery cells/modules ... but maybe that's overkill too ? thoughts ?

The Ford crossflow should work well on the Marlin, I would have thought (Ford Cortinas were the other popular base vehicle back in the day).


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## brian_ (Feb 7, 2017)

Richard500 said:


> Can you remind me how the voltage/current calcs work ... I think you said you ran yours @ 150v and 500 amps ? ... & what made you choose those values? ... am just checking ('cos its a while since I thought this through), and I think you vary the current to vary the motor speed, and use the highest voltage the motor can take (so as to reduce the current required to get the required power to move the car) ? ... I think ?


Voltage and current are not independent: you apply voltage to a motor and an amount current flows dependent on the voltage and speed; you make current flow through a motor and that requires an amount of voltage dependent on the current and speed. You can't pick a current flow and separately pick a voltage at the same time.

The position of the accelerator pedal is interpreted as a target amount of current, proportioned to the maximum allowed by the controller or the maximum the available voltage will make flow, depending on the controller and programming.

What you do need to choose is the motor (which determines how voltage and current are related), and the battery voltage (which determines the maximum voltage that the motor can get and thus how fast it can turn), and the current limit (which determines maximum torque). Of course the motor is limited in how much current it can handle and for how long, and controllers are limited in their input voltage, output current, and power. The motor may never see the maximum (battery) voltage and the maximum (controller-limited) current at the same time.

The faster the motor is turning, the more voltage is required to make a given current flow. That's okay, because it also means more power is being produced (in a turning shaft, power is torque multiplied by speed).

By changing motor choices and gearing, you can change the balance between current and voltage: for example, 300 amps at 50 volts and 100 amps at 150 volts are both 15 kW (power is simply voltage multiplied by current), and enough to keep the car moving at highway speed, but one combination is likely to be more efficient than the other for a given motor. Motors used in modern EVs are generally designed to work with up to 360 volts for their highest speed; most of the less expensive motors used in EV conversions are designed for much lower voltage.


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## Duncan (Dec 8, 2008)

Richard500 said:


> Re. DC Forklift - yes, I think you're right - I suspect the main challenge is to figure out where to source one from around here - will have to do some thinking.
> Re. EV weight vs. IC weight - yes I worked out that they are pretty much on a par if you include a full petrol tank, the EV batteries still come out a bit heavier, but not hugely.
> 
> Can you remind me how the voltage/current calcs work ... I think you said you ran yours @ 150v and 500 amps ? ... & what made you choose those values? ... am just checking ('cos its a while since I thought this through), and I think you vary the current to vary the motor speed, and use the highest voltage the motor can take (so as to reduce the current required to get the required power to move the car) ? ... I think ?
> ...


Hi Richard
Brian's explanation is correct - but maybe not that clear
You have a throttle pedal - this tells the controller what current you are requesting
So if you have 500 amps as max then full throttle = request for 500 amps
Half throttle = request for 250 amps

The Current = Torque - the amount of "push" that your car is going to see, - 500 amps with a 9 inch motor will make your Moss fly up the steepest hills in top gear

The controller meets your "request" by altering the motor voltage - when stationary it only takes about 10 volts for your 500 amps
As the motor revs rise the controller increases the volts to meet your demand - until it reaches the battery voltage then it can't increase any more

So the combination of
9 inch forklift motor, 500 amps and 150 volts is about right for a lightish car and about 80 mph top speed
If you use say 100 volts you will probably struggle to reach 60 mph
And the 500 amps and about 150 volts is the size of most reasonably priced DC controllers 

I'm using most of a Chevy Volt battery pack - very common in the USA - 16 kwh is about $2000US
There is a local Hot Rod part importer that brings containers in from the USA - I got them to bring a Volt battery in for me


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## brian_ (Feb 7, 2017)

Duncan's explanation is good, although "pedal requests current" can't really be correct at high motor speed for a reasonable vehicle, as it would mean that the motor would reach full output in only first third of pedal travel at the highest road speed, with the rest of the pedal travel doing nothing more. That would be stupid... but of course some controllers may still work that way.


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## Duncan (Dec 8, 2008)

brian_ said:


> Duncan's explanation is good, although "pedal requests current" can't really be correct at high motor speed for a reasonable vehicle, as it would mean that the motor would reach full output in only first third of pedal travel at the highest road speed, with the rest of the pedal travel doing nothing more. That would be stupid... but of course some controllers may still work that way.


Its not quite as extreme as that as the back EMF is proportional to rpm and current - but yes when I only had 120 volts I would hit the max current at just over a third of throttle at 100 kph


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## Richard500 (Mar 12, 2021)

brian_ said:


> Voltage and current are not independent: you apply voltage to a motor and an amount current flows dependent on the voltage and speed; you make current flow through a motor and that requires an amount of voltage dependent on the current and speed. You can't pick a current flow and separately pick a voltage at the same time. The position of the accelerator pedal is interpreted as a target amount of current, proportioned to the maximum allowed by the controller or the maximum the available voltage will make flow, depending on the controller and programming.
> What you do need to choose is the motor (which determines how voltage and current are related), and the battery voltage (which determines the maximum voltage that the motor can get and thus how fast it can turn), and the current limit (which determines maximum torque). Of course the motor is limited in how much current it can handle and for how long, and controllers are limited in their input voltage, output current, and power. The motor may never see the maximum (battery) voltage and the maximum (controller-limited) current at the same time. ...





Duncan said:


> The controller meets your "request" by altering the motor voltage - when stationary it only takes about 10 volts for your 500 amps
> As the motor revs rise the controller increases the volts to meet your demand - until it reaches the battery voltage then it can't increase any more ...


Hi Guys,
Thanks for your explanations ... it makes a lot more sense now. So it seems much is dependent on what motor & controller I can get hold of, and then the battery set-up follows on from there, but as long as I get enough battery cells then I can configure them in series and parallel to make up the required output voltage.



Duncan said:


> So the combination of
> 9 inch forklift motor, 500 amps and 150 volts is about right for a lightish car and about 80 mph top speed
> If you use say 100 volts you will probably struggle to reach 60 mph
> And the 500 amps and about 150 volts is the size of most reasonably priced DC controllers


... again thanks. This does sound like a good set-up. I guess it's time to do some research on forklift motors and local warehouses that might be a good place to source them. I was looking at one UK company who was recommending a Netgain Hyper 9 motor which retails at £4,200 in the UK, which seemed a bit steep to me ( ... so a used DC forklift sounds much more realistic 🙂).

Thanks for your advice, everyone, its given me a lot to think about & I know I'll have more questions along the way, but this forum has been really great to get me started.
Cheers,
Richard


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## MattsAwesomeStuff (Aug 10, 2017)

Richard500 said:


> do some research on forklift motors and local warehouses that might be a good place to source them.


I don't think warehouses are going to be an easy route to finding one.

Here's a primer:

- Look up forklift repair places in your area, and call all of them. If you're lazy, call the ones that seems the most mom & pop, not corporate. The cheap one that'll have a boneyard and "just in case" dead lifts being gutted for parts. Anywhere that sells used forklifts too. You can try email, but you'll probably get ignored.

- Drive to any that are nearby, just show up cold and tell them you have a weird question (to set the stage), that someone told you to try calling them (pre-vetted as you not having this crazy idea yourself), that you have a recycling/science project that needs an old junk DC motor and ask if they have any junkers you could use your own tools and time to take off. Many places, these old motors have so low value, they're not even removed from the frame and just scraped for the iron value (1% of the copper value). If they're nice, they'll say it's free, don't hurt yourself. If they're really cheap, they'll want you to cover their scrap value ($100-200), if they're too professional and fancy and corporate they'll say no, you can order from our catalog for $5000.

- If you can, drive around back and introduce yourself to the shop guys directly, instead of the office. Ask them if that might be something you can do. Chances are the front office doesn't even know what they're doing or care, and they might say "Yeah, we have a half dozen 'just in case' salvaged motors and we've never in 30 years needed one, I'll go get you one." Or they might go to the front and say "Someone wants an old junk motor for a project, the Hyster by the fence is already stripped of everything we want, can they have the motor?" Or they might say "I don't know, you'll have to talk to the office", to which you reply "Okay, before I do, is there a wreck or two that you have in mind that would work?" and then you go to the office with this information "Hi, your guys in the back sent me to talk to you, I have a project... ... and they suggested there's a Clark they're about to send off to scrap that has a motor about that size" so there's a little momentum and less of a problem to solve. Makes it easy to just have them page the back and say "We're sending him through."

- Forklifts will have a drive motor and a lift motor, maybe some other motors. Usually the drive motor is the biggest and best. You want one with 4 obvious terminals. The pumps aren't designed to run in reverse so they might only have 2 terminals on the outside. It's not a dealbreaker, it just means you have to cut a conductor inside them and break out each side. Not worth the effort unless nothing else is available.

- You want something roughly 9-11" in diameter.

- You want to grab the coupler that the motor mates to on the gearbox side. You might spend more time getting this off than getting the motor off. It will save you any extra machining or sourcing issues. You'll now have something you can weld to what the engine used to output to the transmission, easy coupler.

- Grab cables if you can, they'll be handy. They're solid copper so they might already be gone or they'll want extra for them.

- The motor is heavier than you can lift. When that last bolt comes out, it's smashing everything in its way until it's in the dirt. Hands, feet, face, anything. Be prepared with straps and such to take the weight and a hand-truck or trolly to move it. Or ask "When I have it loose, should I roll it to the gate or is there a hand truck I can borrow?" there will be a hand truck you can borrow, everything this place moves is heavy.

- If you want, check the condition of the motor brushes first. They're probably fine. If you have choices, choose one with more brush life. Choose one that looks the least rusty too.

- Bring a can of brake cleaner. Everything will be soaked in hydraulic fluid and filthy and slippery.

- Plan on bringing the wrong tools and needing to make a second trip. Bring a can of penetrating oil to hose everything with before you leave, to have better luck the next day.

- Be careful about asking to borrow their tools. Small chance they'll let you, and you just became a nuisance to them.

If you're stuck, ask here for help.


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## Richard500 (Mar 12, 2021)

MattsAwesomeStuff said:


> I don't think warehouses are going to be an easy route to finding one.
> Here's a primer: ...


Thanks Matt,
Yep, makes sense, will definitely give it a try. MIght have to wait a bit until lockdown eases over here, to show up cold to some of these places, but this covid stuff can't last forever (at least not at this intensity), and I can start figuring out who & where and phoning round.
Cheers, Richard


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## bawfuls (Jan 8, 2018)

For the Spitfire either go with something like the Hyper9 coupled to a single speed reduction gear, or get a small Tesla motor and replace the entire rearend/subframe. It can be very difficult to get an electric motor dialed in just right to an oem clutch and transmission, you’re likely to get some vibration.


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## Duncan (Dec 8, 2008)

bawfuls said:


> For the Spitfire either go with something like the Hyper9 coupled to a single speed reduction gear, or get a small Tesla motor and replace the entire rearend/subframe. It can be very difficult to get an electric motor dialed in just right to an oem clutch and transmission, you’re likely to get some vibration.


I'm trying to think of a WORSE solution to the problem!
Nope I'm not in a creative enough mood today


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## bawfuls (Jan 8, 2018)

Just speaking from my experience mating electric to the stock transmission. It had an obvious appeal when I began my project (simplicity, getting to keep the manual shifting feel, etc). But in the end I'm not really satisfied with it and I wish I'd just gone the direct drive tesla route (I'd also like the additional power).

I'm not sure why this board is still so obsessed with reclaimed forklift motors despite so many quality OEM parts being available now. 10 years ago it made a lot of sense but now there are other options. I guess if you're trying to do things on the cheap, but that's kind of a contradiction when we're talking about ev conversions.

For something so light, a Hyper9 or equivalent with a (properly selected) single reduction gear seems like a fine fit. This is exactly the kind of thing ZeroEV did with their Miata project, which is well documented on their youtube. 



 or you can see Jonny Smith paying with that car here: 




If you can get away with avoiding a transmission, I'd recommend it.


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## brian_ (Feb 7, 2017)

bawfuls said:


> For the Spitfire either go with something like the Hyper9 coupled to a single speed reduction gear...


That would work fine, but...


bawfuls said:


> ... or get a small Tesla motor and replace the entire rearend/subframe.


That's unreasonable. No Tesla drive unit and subframe will work with the Spitfire frame, and they are all far too large for the Spitfire or a kit based on it. Even the smaller Model 3 is a foot wider than any Spitfire, and uses tires which are substantially larger.


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## Duncan (Dec 8, 2008)

bawfuls said:


> Just speaking from my experience mating electric to the stock transmission. It had an obvious appeal when I began my project (simplicity, getting to keep the manual shifting feel, etc). But in the end I'm not really satisfied with it and I wish I'd just gone the direct drive tesla route (I'd also like the additional power).
> 
> I'm not sure why this board is still so obsessed with reclaimed forklift motors despite so many quality OEM parts being available now. 10 years ago it made a lot of sense but now there are other options. I guess if you're trying to do things on the cheap, but that's kind of a contradiction when we're talking about ev conversions.
> 
> ...


I agree completely about using quality OEM parts from crashed cars
But a Hyper 9 has no advantages over a forklift motor - its just wimpier and a LOT more expensive

Why pay a lot more for something that is not as good??


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## bawfuls (Jan 8, 2018)

Everyone has difference tolerances for the amount of tinkering and custom built kit they're willing/able to do. A Hyper9 is much more plug-and-play than a salvaged forklift motor, for some that's worth the cost.


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## Duncan (Dec 8, 2008)

bawfuls said:


> Everyone has difference tolerances for the amount of tinkering and custom built kit they're willing/able to do. A Hyper9 is much more plug-and-play than a salvaged forklift motor, for some that's worth the cost.


Plug and play ++++ WIMPY!


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## bawfuls (Jan 8, 2018)

Says the guy who built a whole car from the ground up


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## brian_ (Feb 7, 2017)

Duncan said:


> I agree completely about using quality OEM parts from crashed cars
> But a Hyper 9 has no advantages over a forklift motor - its just wimpier and a LOT more expensive
> 
> Why pay a lot more for something that is not as good??


While I'm not sold on the HyPer 9 as a good deal, or an ideal EV motor, it is not just an overpriced brushed DC series-wound "forklift" motor like a WarP 9 - it is a synchronous internal permanent magnet / reluctance motor.



Duncan said:


> Plug and play ++++ WIMPY!


Is the output of a HyPer 9 any less than a typical 9" forklift motor as implemented in a DIY conversion? Let's compare power and torque curves... oh, right, no one has those, especially for the forklift motors.


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## kumar0raja (Apr 9, 2021)

Currently I run 1200 amps - but this is excessively exciting when I have my cheap road tyres fitted - so for road use I have a resister switched into the throttle circuit
This drops me back to 40% - about 500 amps - which is more than enough to make it a fast road car

The voltage is needed to get highway speed - 150 volts and a 9 inch motor is more than enough to maintain 500 amps up to 80 mph
boi hrms
teatv


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## Richard500 (Mar 12, 2021)

Sounds good, thanks for the confirmation ... I think that's the road I'm going to try & go. First on the to-do list is to find a motor that doesn't cost too much, ... out of curiousity, what is the general opinion of a fair price for a second hand 9" motor ? (the £4200 I was quoted for a new Hyper-9 is a fair bit more than the car is worth, so that doesn't fly - even though I would be v happy to do the plug-and-play wimpy thing if the price made more sense ).


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## Duncan (Dec 8, 2008)

Richard500 said:


> Sounds good, thanks for the confirmation ... I think that's the road I'm going to try & go. First on the to-do list is to find a motor that doesn't cost too much, ... out of curiousity, what is the general opinion of a fair price for a second hand 9" motor ? (the £4200 I was quoted for a new Hyper-9 is a fair bit more than the car is worth, so that doesn't fly - even though I would be v happy to do the plug-and-play wimpy thing if the price made more sense ).


I have paid between $100NZ and $200NZ - so that is between 50 pounds and 100 pounds


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## Richard500 (Mar 12, 2021)

Duncan said:


> I have paid between $100NZ and $200NZ - so that is between 50 pounds and 100 pounds


Thanks Duncan,
I suspect it's going to be a challenge to match that, but it gives me something to aim at.
Cheers, R


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## brian_ (Feb 7, 2017)

Richard500 said:


> ... out of curiousity, what is the general opinion of a fair price for a second hand 9" motor ? (the £4200 I was quoted for a new Hyper-9 is a fair bit more than the car is worth, so that doesn't fly...


The £4200 would be for a PMAC motor (not brushed DC) with a three-phase controller. The $100 price of a salvaged motor is for an old used brushed DC motor only, with no controller.


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## Richard500 (Mar 12, 2021)

brian_ said:


> The £4200 would be for a PMAC motor (not brushed DC) with a three-phase controller. The $100 price of a salvaged motor is for an old used brushed DC motor only, with no controller.


Hi Brian,
Yes, correct & understood ... am thinking £4200 + £X,000 for Li batteries + £Y00s for wiring, instruments & welding battery cases etc. is probably a bit too steep for a car that's probably worth ~ £3,000 currently as an ICE (admittedly it might be worth a bit more as an EV) ... so this project needs to be tailored to the scale of the base car. If I had a Lamborghini to retro-fit ... different story (& I'd probably just be paying the man his £20k to do it for me anyway ).
Cheers, R


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