# anyone go with clutch? just to rev the motor?



## TeZla (Feb 18, 2021)

my thoughts is that its kinda dumb.
Electric motors are almost completely silent, not sure what noise you expecting to hear when you rev it, but you'd be better off with a sound generator and then you can play any engine sound you want, even a lada if that really tickles your fancy.

From a mechanical point of view, your proposing to keep the clutch, which adds rotational weight (Flywheel, pressure plate, clutch disc, clutch arm, throwout bearing etc) for no purpose and creates a weak point (the clutch disc) that'll fail under the high instant torque output of the motor.
Do you want to change gears while driving? Why? The useable rpm range of an electric motor makes that virtually pointless and if you did want to change gears while moving, its pretty simple to match the rpm's, use the syncros and shift up or down gears. its something that you would program into your inverter/controller and have a little practice while driving.


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## brian_ (Feb 7, 2017)

Many builders who use the original transmission, or another similar transmission, keep the clutch. While it is not needed for the usual reason (with an engine) of slipping to avoid stalling the engine, it is helpful for shifting. Shifting allows different ratios to be used for different driving speeds and conditions, but in practice most DIY EV conversions are rarely shifted, even if they are capable of it.

Spinning the motor with no load ("revving" it) would produce no significant sound, and in the case of a brushed DC motor risks destroying the motor because it is easy to over-rev.


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## t0astm0nkey (Jun 23, 2020)

If you can pick a gearcase or transmission with a neutral position, that would be better.
The Brammo/Victory Empulse bikes had a 6 speed gearcase with a clutch - but most rarely used the clutch. @TeZla is correct that it will make relatively little noise, but for EV conversions the noise is usually more pronounced than production EVs due to the lack of sound deadening and typically a less robust design.


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## tj4fa (May 25, 2008)

brian_ said:


> ... but in practice most DIY EV conversions are rarely shifted, even if they are capable of it.
> 
> Spinning the motor with no load ("revving" it) would produce no significant sound, and in the case of a brushed DC motor risks destroying the motor because it is easy to over-rev.


Agree with the over-rev and it will destroy the brushed motor. With no drivetrain load of the vehicle, it would over-rev to death in micro-seconds.


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## lawrencerhodes (Mar 31, 2008)

Keeping a clutch allows you to keep the gearing. However only a weenie thinks reving an electric motor is cool unless you call your car "the sound of silence." They sound cool accelerating and pushing the weight of a vehicle.


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## mikehello (Jun 26, 2021)

lawrencerhodes said:


> only a weenie thinks reving an electric motor is cool


😭the motor i have if you spin it it makes a sound. not like an engine sound but you know what i mean lol


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## mikehello (Jun 26, 2021)

t0astm0nkey said:


> If you can pick a gearcase or transmission with a neutral position, that would be better.
> The Brammo/Victory Empulse bikes had a 6 speed gearcase with a clutch - but most rarely used the clutch. @TeZla is correct that it will make relatively little noise, but for EV conversions the noise is usually more pronounced than production EVs due to the lack of sound deadening and typically a less robust design.


im such a noob i forgot about neutral 😅😲😲😲!


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## gdirwin (Apr 7, 2009)

I kept the clutch, but not for the sound. It makes shifting of a manual transmission easier (some cars are easier to shift without a clutch vs others) plus the safety if the motor controller shorts (ie DC motor drives). I also have a "big red button" to press which opens the battery.


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## remy_martian (Feb 4, 2019)

TeZla said:


> *my thoughts is that its kinda dumb....*
> 
> From a mechanical point of view, your proposing to keep the clutch, which adds rotational weight (Flywheel, pressure plate, clutch disc, clutch arm, throwout bearing etc) for no purpose and creates a weak point (the clutch disc) that'll fail under the high instant torque output of the motor.
> Do you want to change gears while driving? Why? The useable rpm range of an electric motor makes that virtually pointless and if you did want to change gears while moving, its pretty simple to match the rpm's, use the syncros and shift up or down gears. its something that you would program into your inverter/controller and have a little practice while driving.


Much of what you wrote is "kinda dumb"

A clutch disc has much lower rotational inertia than a direct coupled motor rotor. That means smoking your syncros in no time if you speedshift your electric motor, even with your skillful matching of RPM, even with current cut off, with no clutch. It's not "simple" at all because the rotor is so massive...you'll smoke the syncros. Ever notice how light clitch discs are, how their mass is minimalized as radius increases? Ever look at the friction surfaces on a synchro?

Changing gears multiplies torque. You want 0-60? Yeah, low gear. You want top speed? Yeah, motor geared for that 0-60 won't get you there.

Not to mention efficiency, since most 1:1 ratios on transmissions these days are extremely efficient...but your 0-60 is gunna suck if you keep it 1:1.

So, yes, there's a reason the Rimac and the Rimac-sourced Taycan has a two speed gearbox. There's also a reason why Tesla Roadster 1.0 moved away from one.

Half the fun is working the tradeoffs in any EV design, whether OEM or shadetree mechanic. There's nothing "dumb" about including or deleting a transmission. Or, wanting to rev the motor...then dumping the clutch for even crazier launch torque.

To the point of revving for the sound, who's to say whether he's got a playing card clipped on with a clothespin or not? You all assume silence, sound deadening, rubber isolators, etc.


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## TeZla (Feb 18, 2021)

remy_martian said:


> Much of what you wrote is "kinda dumb"
> 
> dribble dribble dribble, etc.


cool story bro.
would have been cooler a few months ago rather than getting on your high horse on a zombie post...

Do whatever you want, im not the boss of anyone


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## remy_martian (Feb 4, 2019)

I posted 8 hours after the previous poster.

The high horse I got on is the one you fell off of


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## TeZla (Feb 18, 2021)

lol, nice come back, Such an absolute zinger. 
I see we've found the expert in all things and greatest man that ever lived. Oh my shock to see its an American...

run along child


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## remy_martian (Feb 4, 2019)

Second greatest

Obviously


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## TeZla (Feb 18, 2021)

Thats right bitch tits, remember your place


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## brian_ (Feb 7, 2017)

remy_martian said:


> ...
> There's nothing "dumb" about including or deleting a transmission. Or, wanting to rev the motor...then dumping the clutch for even crazier launch torque.


Increasing motor speed then "dumping" the clutch doesn't increase motor output torque at all, since electric motor torque doesn't increase with speed; the fundamental reason for doing this with a combustion engine doesn't apply in an EV conversion. There is the flywheel effect, but all that does is provide a spike of torque for the period of time that the clutch slips, which in turn does nothing except risk breaking tire traction. If tire smoke is the goal, by all means get the highest-interia motor and the heaviest flywheel that your bearings can stand, and dump away. For everyone else, if you use a clutch then minimize the flywheel inertia.

I agree that there are arguments for and against using a multi-speed transmission, and that the decision depends on factors such as the vehicle context and the builder's goals and abilities.


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## yves.carrier (Nov 21, 2021)

I personnally plan to reuse my manual transmission for my EV conversion project for 2 reasons.
1- I may be wrong but I feel like fitting a new motor to the current transmission would be easier than fitting it to the driving assembly if I remove the transmission

2- from a design stand point, since I kind of guess the required torque vs speed of my vehicle, having the ability to shift the transmission gear will mechanically "tweak" the motor's torque vs rpm curve so that I will have a level of flexibility to adjust the motor's drive the the vehicle behavior. As a general rule, I expect that using a lower gear will increase the motor's rpm for a particular vehicle speed, taking down the required torque for a particular number of required HPs, requiring less current to flow in the motor and as a result, keeping the motor temperature lower. This is really a totally different minding than for a combustion engine... Obviously, it makes sense only if your maximum RPM remains within the operation zone specs of your motor.

And I think that when I will find this sweet spot gear ratio, I will rarely shift the transmission gears except for very specific circumstance.

Comments and ideas are welcome.

And regarding the sound "problem" reported at first, I would personnally use a getho blaster with pre-recorded combustion engine sounds having its volume control connected to the throttle potentiometer... 😁 Just kidding. 😉


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## piotrsko (Dec 9, 2007)

You'll be suprised how noisy the powertrain is.

My Kostov runs like a small block chevy, happiest between 2500 & 3500rpm, 5 forward speeds is handy there, but 10 is overkill so I don't use 4low much. Had to buy a motor adapter and mount system so keeping the rest of the drivetrain stock was a cost reduction.

As my homebrew malt purveyor likes to say "it's yours, make it anyway you like"


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## 52International (Feb 13, 2021)

I think two speeds would be awesome. I've played with the spreadsheets a ton and can't meet two different goals. First is great low end 0-60 with top end maybe 70. Second is for economy and road trips where is like the RPM at 70MPH to be at peak efficiency, around 5500 RPM. That max is 140MPH+. I don't think you'd need to shift on the fly though. 



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## remy_martian (Feb 4, 2019)

Peak efficiency becomes a bit of a lost cause if you put a geartrain in the powerpath or try to push a brick through the air where 5MPH eats the gains up.


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## brian_ (Feb 7, 2017)

remy_martian said:


> Peak efficiency becomes a bit of a lost cause if you put a geartrain in the powerpath...


There's a geartrain in any viable powertrain path. The difference in transmission efficiency of having a two-speed instead of single-speed gearbox would likely be difficult to measure; this assumes, of course, that the gearbox doesn't have something stupid such as a torque converter or traction drive.


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## remy_martian (Feb 4, 2019)

You are going to be dragging more gears through lube on a multispeed, which leads to windage losses on a two speed manual unless it's a planetary two speed. There's increased weight in carrying the extra gears, a shift mechanism, and a larger case for it all.


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## 52International (Feb 13, 2021)

Well the only way I know to get what I'd like is to have two gear boxes in a row. I don't think running 11,000 RPM into anything made for a 6,000 RPM has engine is a good idea. So start of with the first reduction, then the two speed box. 

This, yes, there's a who lot of extra drag in this scenario. 

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## remy_martian (Feb 4, 2019)

Why not make the truck front wheel drive?


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## brian_ (Feb 7, 2017)

Yes, a multi-speed manual transmission has more lube drag than a single-speed, causing a drop from what - 97% to 96% transmission efficiency? Two gearboxes in sequences would be less efficient, and the input speed capability of a transmission intended for use with a car or truck engine is a concern.





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5 Transmissions | Cost, Effectiveness, and Deployment of Fuel Economy Technologies for Light-Duty Vehicles |The National Academies Press


Read chapter 5 Transmissions: The light-duty vehicle fleet is expected to undergo substantial technological changes over the next several decades. New pow...



www.nap.edu


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## brian_ (Feb 7, 2017)

remy_martian said:


> Why not make the truck front wheel drive?


Because the result would be a front wheel drive 1952 International truck.


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## remy_martian (Feb 4, 2019)

ELECTRIC 1952 truck 😂


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## 52International (Feb 13, 2021)

Hey Brian, Remy, thanks, this truck is going to be awesome!

I've narrowed down to two options for the truck I first learned to drive as a kid at grandma's farm. The best option is intimidating as I need to build my own chassis. I just wonder how long the wait list is for the Ford ecrate. I would need two of them for 4x4.

Just about time to start my own thread and quit hijacking others threads. 

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