# Ideal vehicle for conversion



## Buckster (Nov 4, 2009)

When I joined here the other day I was pretty sure I would see a trend for particular vehicles pointing to the ideal but I'm much more confused now with the myriad of choices, I thought the Fiero may be a good choice but can see that it will be problematic if I want lots of range which requires lots of batteries, I would also like to try direct drive with no gearbox but can see problems with reverse, certainly with a DC set up. On the other hand the build pages have given me some real insight into what is possible. Ideally I think a front engine rear drive donor makes the most sense as a first build but a spaceframe kit car of some sort set up for mid engine would be the ultimate choice in the long term, choices choices.


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## Woodsmith (Jun 5, 2008)

Given a sensible build budget I would probably look at using one of two option types as a base vehicle.

Four wheeler: A 2+2 seat rear drive car with a motor in the tunnel driving through a small marine gearbox to give a variable selection and reverse. The final drive ratio would need to be suitabley matched to the marine gear box. The front of the car would hold most of the battery pack with the rest in the mid area where a fuel tank may have been. This may give a good weight balance.

Three wheeler: A 1+1 rear drive car with a motor bike style shaft drive to the rear wheel. A standard width front suspension assembly that is factory designed so it works. The battery pack would be under the floor with the motor under the rear seat giving direct drive with electric reverse. The body shell will be narrow to fit the seating arrangement.

However, in reality the ideal car is often the least bad budget buy that suits the immediate need and where the model has been converted by someone else before so it is known to be doable.


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## MJ Monterey (Aug 20, 2009)

Ideal car would depend on what do you want the car to do.

O.k. you have determined that an EV would be cool to have. Now what are your requirements for this car. Do you need to carry one, two, four or six people? Pets? Lots of groceries or just a sandwich and drink?

Is this a commuter(length of commute, recharge at work)? Only used it to run up to the store for groceries and odds and ends? Or just for cruiseing to the burger joint on Friday and Saturday nights for a malt?

In town only or high speed freeway capable?

Temper the outcome from these questions with your personal fabrication skills. Figure out YOUR ideal starting spot and go from there.


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## everanger (Sep 7, 2009)

I sted with a ranger pick up it was cheap and easy to do,but heavy and room for 2
next was the sandrail we had it very easy to do great performance but room for 2 and not practical for normal commute not to mention cold right now.
next thought is a small car or suv room for 4, enclosed and good performance


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## Buckster (Nov 4, 2009)

MJ Monterey said:


> Temper the outcome from these questions with your personal fabrication skills.


Almost unlimited in respect to vehicles, I have been engineering solutions for over 20 years including building aircraft etc. as to my desired outcome, well that will evolve with the vehicle, the marine gearbox idea sounds interesting.


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## 280z1975 (Oct 2, 2008)

For the best range you might go with the Ford Ranger (or other light duty pick up) as you can load up the back with batteries (lifepo is better) to get lots of range, but be sure to strip the car of as much un-needed weight as possible and if you can, modify the body for optimal aerodynamics. 

Less weight ... less CD ... and small frontal area are the keys to efficiency. Just take stock of your real needs (not wanted, as those are going to be $$$) and then build the car around those needs. 

-Gregg-


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## Woodsmith (Jun 5, 2008)

The marine gearbox is just an idea, I've never looked into the practical use of one but from what I gather they have a moderately variable ratio (sometimes steplessly variable) and reverse. Seems ideal for EV use if the ratios are suitable. Just need a speedo pick up from somewhere so satisfy local laws.

I just missed bidding on a small marine gearbox the other day on Ebay, It was only £30 but I couldn't get the bid in in the few seconds left when I saw it.


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## MJ Monterey (Aug 20, 2009)

Fab skills! check!

Another avenue to check out would be a kit/replica cars. Factory 5 has the Cobra kit that has been successfully converted. http://www.ssi-racing.com/

Also B.C. (a member here http://www.diyelectriccar.com/forums/member.php?u=8589) is beginning to look at producing a kit.


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## Buckster (Nov 4, 2009)

Woodsmith said:


> The marine gearbox is just an idea, I've never looked into the practical use of one but from what I gather they have a moderately variable ratio (sometimes steplessly variable) and reverse. Seems ideal for EV use if the ratios are suitable. Just need a speedo pick up from somewhere so satisfy local laws.
> 
> I just missed bidding on a small marine gearbox the other day on Ebay, It was only £30 but I couldn't get the bid in in the few seconds left when I saw it.


If you used a hydraulic gearbox with trolling valve for low gear it should work having had a look at one at the weekend. I keep coming back to hydrostatic drives everytime I look at EV's, it just seems to be the right solution.


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## Woodsmith (Jun 5, 2008)

Buckster said:


> If you used a hydraulic gearbox with trolling valve for low gear it should work having had a look at one at the weekend. I keep coming back to hydrostatic drives everytime I look at EV's, it just seems to be the right solution.


From what I gather hydrostatic has huge losses in efficiency and needs a lot of power to run them.

The ideal I guess would be to have no transmission elements but outside of wheel motors that is not always practical.
A motor on the final drive is the next option but can cause inefficent running when not driving at the optimal motor speeds.
For most drivers I think a couple of gears and a reverse gives the simplest solution in many ways hence simple mechanical marine boxes came to mind. 
Auto boxes without the torque converters are also figuring in my thoughts.


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## Buckster (Nov 4, 2009)

Woodsmith said:


> From what I gather hydrostatic has huge losses in efficiency and needs a lot of power to run them.


Maybe in the olden days, efficiency of variable drives is generally 80 - 90% now which puts it roughly equivalent to an automatic gearbox, the problem I can see with a marine gearbox is that it is not built to handle the reverse loading it would get in a car, i.e. the feedback from the driven wheels back through the gearbox and the general shock load capabilities are much lower as the only resistance they experience is driveline load, output being into a fluid medium rather than a direct friction component of tires on asphalt. However another possibility would be a small industrial parallel shaft gearbox, these have high shock loading, are good in reverse torque applications and can be very compact. Of course a two speed with reverse built for ev is the ideal like the one offered by Vocis in the UK. Another alternative would be a variation of a two speed differential/axle, unfortunately existing units are usually very heavy as they are designed for heavy pick up trucks.

I think there are certainly a number of options worth exploring.


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## dragster (Sep 3, 2008)

Hi
You are replacing a gas engine with an electric engine and lots of heavy batteries. hello hello!!! (you need a transmission.) and not a boat transmission.


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## Buckster (Nov 4, 2009)

dragster said:


> Hi
> You are replacing a gas engine with an electric engine and lots of heavy batteries. hello hello!!! (you need a transmission.) and not a boat transmission.


Try reading all of it, hello hello! We were discussing ways of getting away from the existing automotive transmission to one that provides the required gearing rather than one that is carrying excess weight and gears, some people actually like to think a project through and bounce ideas around.


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## Woodsmith (Jun 5, 2008)

The boat transmission came from me and it was based solely on the idea that sometimes 2 gears and a reverse is all that is really needed from the transmission system. It was also said earlier on that it would need to have appropriate ratios and be able to handle the loads and require a speedo connection in some cases.

It is just an idea from someone who has scratch built and adapted transmissions sucessfully in the past for for alternative uses.

The bouncing around of ideas is always a good thing as sometimes there is some wheat mixed in with the chaff.

No one ever said 'Don't use pvc pipe, use a proper vacuum reserviour!', or 'Use a proper automotive traction motor not a large dc series motor from an industrial machine!'.


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## Buckster (Nov 4, 2009)

I would like to explore using two motors and a reversing gearbox like this one from Quaife.


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## dragster (Sep 3, 2008)

Hi
I have no problem bouncing ideas around however you may not like the automotive industries as it is today but the best engineers in the world have spent 100 years trying to make the lightest and lest amount of friction used in the transmission so the vehicle can get the best MPG it can. As for boating I have been boating for 30 years and the transmissions are not suitable for driving 60 MPH on the highway.


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## Jan (Oct 5, 2009)

dragster said:


> Hi
> I have no problem bouncing ideas around however you may not like the automotive industries as it is today but the best engineers in the world have spent 100 years trying to make the lightest and lest amount of friction used in the transmission so the vehicle can get the best MPG it can. As for boating I have been boating for 30 years and the transmissions are not suitable for driving 60 MPH on the highway.


Yes, but they are also designed for engines with a compleet different power (or if you prefer torque) / rpm curve. So, it's a good thing to look for alternative gearing options.


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## Buckster (Nov 4, 2009)

dragster said:


> Hi
> I have no problem bouncing ideas around however you may not like the automotive industries as it is today but the best engineers in the world have spent 100 years trying to make the lightest and lest amount of friction used in the transmission so the vehicle can get the best MPG it can. As for boating I have been boating for 30 years and the transmissions are not suitable for driving 60 MPH on the highway.


So you are saying that all those transmission were designed were for electric vehicles? I have nothing against the automotive industry but you seem to have a problem with someone, I am not sure who exactly, perhaps the voices.


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## Buckster (Nov 4, 2009)

Back to reality, the ignore function is a wonderful thing, has anyone got any experience of running two motors in series to get past the gearbox requirement?


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## Woodsmith (Jun 5, 2008)

dragster said:


> Hi
> You are replacing a gas engine with an electric engine and lots of heavy batteries. hello hello!!! (you need a transmission.) and not a boat transmission.


This post was not useful.



dragster said:


> Hi
> As for boating I have been boating for 30 years and the transmissions are not suitable for driving 60 MPH on the highway.


This one was a bit more useful.

Had you said that in the first place then I would have asked for your advice on what the limiting aspects are and then looked in to maybe scratch building a box that used the functions of a marine gearbox and the requirements of an automotive one.

However, in my plans to build an EV I have come across a great many people who have said that a series DC motor from a forklift couldn't be used or clutchless is no good or a small car wouldn't have space for batteries. I'm sure Harley Davidson had someone who said a bike can't be driven with a rubber belt yet there are now cars that have a rubber belt drive in the transmission system.


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## Buckster (Nov 4, 2009)

What are the usual ratios of a marine gearbox? I think the ideal for a smallish ev would be 1.6:1 and 1:1.


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## Woodsmith (Jun 5, 2008)

Buckster said:


> I would like to explore using two motors and a reversing gearbox like this one from Quaife.


The Quaife box looks interesting. Being a direct drive you would need to look at the effects of the final drive ratio if you were driving into a diff, or if you were thinking of two motors and two boxes, one to each wheel, then the gear ratio could become more of an issue depending on the torque and speed charateristics of the motors you want to use.

Perhaps having a geared motor, like some of the industrial units, attached to the Quaife could give the correct ratio.

I think the general idea with direct drive is a ratio is around 6:1.

I have also looked at the old Laycock type overdrive units as used on old MGs and Jaguars. The design is fairly simple with a cone clutch to select between two ratios. Making one work backwards to get a step down would be fun as the integral pump would be driven by the output rather then the input.


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## Buckster (Nov 4, 2009)

Woodsmith said:


> The Quaife box looks interesting. Being a direct drive you would need to look at the effects of the final drive ratio if you were driving into a diff, or if you were thinking of two motors and two boxes, one to each wheel, then the gear ratio could become more of an issue depending on the torque and speed charateristics of the motors you want to use.
> 
> Perhaps having a geared motor, like some of the industrial units, attached to the Quaife could give the correct ratio.
> 
> ...


I was thinking of two Warp 9's in series to give the torque for hill climbing and low end acceleration, perhaps running a 160v set up, then rely on the ratio of the diff which will be about 3.5:1 as a general average to give the spread. A ratio of 6:1 overall would be like driving around in second gear all the time.


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## Woodsmith (Jun 5, 2008)

The problem with too high a ratio is that the motors are running at low rpm for most of the driving.
This leads them to be very inefficient and run very hot. Having a lower ratio means that the motors run at higher rpm for more of the time and are, therefore, more efficient and run cooler.

With two 9" motors running at low rpm with a high ratio diff you will generate potentially distructive torque levels in your drive train.

This is, I believe, the usual reason for retaining the gears when using a dc series motor. Most of the driving is then done in 2nd and 3rd is used for higher motorway speeds.


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## Buckster (Nov 4, 2009)

Woodsmith said:


> The problem with too high a ratio is that the motors are running at low rpm for most of the driving.
> This leads them to be very inefficient and run very hot. Having a lower ratio means that the motors run at higher rpm for more of the time and are, therefore, more efficient and run cooler.
> 
> With two 9" motors running at low rpm with a high ratio diff you will generate potentially distructive torque levels in your drive train.
> ...


Having done the math now I see you are completely correct, so unless it is a town commuter you just cannot get away from some sort of gearbox, with standard 55 profile 16" tyres you are looking at about 406 wheel revolutions per minute to achieve 30mph, with a 3.5:1 diff this equates to 1500 rpm from the motor, most series DC motors have a sweet spot of around 3000 to 3700 rpm, however if you went to a parallel DC motor like the warp 13 then you get high efficiency at low rpm, say 1000 upto 3000 where you are still getting 70% efficiency. However you are right there in AC motor territory on price, so you would be within $2-3k of the price of a full AC setup, which has the potential of being a far better overall vehicle with a simple reverse function on the motor, available reduction drives and with a greater efficiency spread will give better range with the same batteries.


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