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explain clutchless shifting

11624 Views 15 Replies 9 Participants Last post by  Manntis
I am obviously a novice at this ev converison but am determined to have one up and running by next spring.. I am studying everything i can get my hands on as well as scouring the internet. I just have one simple and i mean simple question about a direct drive without using a clutch/flywheel etc.. What exactly are you keeping on the transmittion and how does it shift without the clutch etc...? please help.. thanks!
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I am obviously a novice at this ev converison but am determined to have one up and running by next spring.. I am studying everything i can get my hands on as well as scouring the internet. I just have one simple and i mean simple question about a direct drive without using a clutch/flywheel etc.. What exactly are you keeping on the transmittion and how does it shift without the clutch etc...? please help.. thanks!
Some keep the clutch, some just shift at the proper RPM like you can do on a regular manual car.

As for keeping the transmission, it's about ratios. If your motor RPM is, say, 2,000 and you're going direct drive, you're turning your driveshaft at 2,000 RPM - which may not be desirable given the torque or speed you're attempting to attain.

Keeping the transmission allows you to keep a reduction ratio.
 

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I just have one simple and i mean simple question about a direct drive without using a clutch/flywheel etc.. What exactly are you keeping on the transmittion and how does it shift without the clutch etc...? please help.. thanks!
It depends on what you mean by direct drive.

By the way you worded your question, I think you might be referring to hooking the motor "directly" to the gearbox without a clutch. In this situation an adapter is normally made from an old clutch plate that hooks the motor shaft solidly to the gearbox input shaft with no way to dis-engage it. You remove the WHOLE clutch assembly. None of it is used. Not the flywheel , the peddle, nothing!! When you want to change gear it is made possible by the fact that an electric motor has virtually no mass(compared to an ICE motor). This allows the syncro's in the gearbox to match the internal gear speeds reasonably quickly which allows the gear to be selected. To change gear you just take your foot off the gas and slip the leaver into neutral. You then GENTLY & SLOWLY introduce the gear leaver to the gear you want to select. The syncro's will match the gear speeds and you will "FEEL" the gears mesh and the leaver will sort of "fall" into place. Then you put your foot back on the gas:)

This may sound complicated but it can be done easily with practice and it only takes only a few second longer than changing with a clutch. The important thing is to remember NOT TO RUSH IT!!

You can actually do it with SOME normal ICE cars, but it takes a lot more concentration to use the gass peddle to balance the motor speed to the gearbox speed. It's harder because the the ICE motor has far too much mass for the syncro's to overcome and they can't match the speeds. The clutch helps out here by removing the motor mass from the equation so the syncro's can do their job with only the mass of the clutch plate to deal with.
An electric motor has more mass than a clutch plate thats why you can't shift as fast when you go clutchless in an EV.

Normally, "direct drive" means that the motor is attached directly to the tail shaft of a rear wheel drive car with no gear box at all. You need a large motor for this that is capable of supplying the torque necessary to drive you up hills and your speed is limited by the ratio in your differential and you motor redline. Reverse is attaned by reversing the direction of the motor through the controller.

Hope this helps:)
 

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Excellent explanation. Matt, can we get this moved into the Wiki area?
I second that! Before I've been a bit ambivalent about removing the clutch or not, but after that splendid explanation it sounds like I'm not gonna miss it. Off with the clutch, as the queen of hearts would've put it. :)
 

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Go right ahead, just copy and paste from his post and start a new topic called 'clutch versus clutch-less". I could do it myself but I'm trying to encourage more participation in the wiki.
 

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Excellent, the wiki is starting to work like I've wanted it to all along! :D:D:D
I knew it would pay off, thanks DVR
 

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I drive a 93 honda civic and 97 jeep TJ (both ICE) on a regular basis. I can shift both with out the clutch. If I drove with out the clutch all the time It would effect my gas mileage negatively I believe. I can't confirm that though. I don't know if that would translate to slightly less range on an EV or not. It seem to me that starting in first gear and shifting up to 3rd would keep things more efficient too.
 

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I've heard that clutchless shifting can be hard on the syncros, more so on some transmissions than others. Also, you do lose the emergency physical disconnect between motor and trans when you remove the clutch. Something to consider.
With a kill switch installed, which should be there anyhow, there's no need for a physical disconnect. :)
 

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You've still got the gear leaver in your hand. Push it into neutral if you need to disconect:)

As far as syncro's go I think the jury is out on whether they suffer in a clutchless setup, they are designed to slip every time the gears are changed in a regular setup. Yes they slip more in an EV but you rarely need to change gear anyway so I believe it's not an issue for normal use.
If your after MAX performance and want to have the motor buzzing in it's sweet spot all the time then yes, you would probably want to keep the clutch. There is however a chance of the inexperienced over revving the silent motor with the clutch in and you also have a lot more rotational inertia which saps acceleration.

Messes with your head dunnit?:D
 

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With a kill switch installed, which should be there anyhow, there's no need for a physical disconnect.
True, though I prefer redundancy.
You've still got the gear leaver in your hand. Push it into neutral if you need to disconect:)
Would there be a problem getting into neutral under load? I've never tried to shift into neutral under full throttle :eek: DC controllers fail full on after all.
As far as syncro's go I think the jury is out on whether they suffer in a clutchless setup, they are designed to slip every time the gears are changed in a regular setup. Yes they slip more in an EV but you rarely need to change gear anyway so I believe it's not an issue for normal use.
Good point.
 

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Just remember: Your clutch/gears would always have to be a last resort because your motor without load would just rip apart in the engine bay with full power but no load... Not something you would want to rely on.
 

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Just wanted to throw in my 2 cents.

My 97 S-10 is clutchless with an ADC motor, 2-1/2" dia. steel coupler, and New Venture 5 speed manual trans. I've been very pleasantly surprised at how smoothly this thing shifts. I generally drive in 2nd gear in town and 3rd gear on the highway (rural NW IL)

2nd gear: 2.37 gear ratio, 3.73 rear axle ratio, 8.84 final drive ratio, 3,000rpm = 26mph, 4,000rpm = 35mph
3rd gear: 1.49 gear ratio, 3.73 rear axle ratio, 5.56 final drive ratio, 3,000rpm = 42mph, 4,000rpm = 56mph

If I shift in the same manner and speed as I did with the ICE, I can feel a very slight drag on the synchros and the shift is smooth. If I take just a 1/2 to 1 second longeer to wait for the motor to slow slightly, the trans falls into gear completely smooth without any drag on the synchros whatsoever.

As far as safety, I can somewhat agree that not having a clutch could be an issue in a runaway, but you're correct that freewheeling a runaway is going to absolutely destruct the motor and probably the coupler and trans input shaft also. My system has three methods of disconnect. The secondary contactor disengages at throttle-off, the primary contactor disengages at key-off, and I mounted an emergency e-stop mushroom style palmswitch/panic button on the dash that kills both the primary and secondary contactor coils if activated. I don't know if I could physically force the transmission into neutral under full power; I really don't want to ever have to try.
 

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My 97 S-10 is clutchless with an ADC motor, 2-1/2" dia. steel coupler, and New Venture 5 speed manual trans. I've been very pleasantly surprised at how smoothly this thing shifts. I generally drive in 2nd gear in town and 3rd gear on the highway (rural NW IL)

2nd gear: 2.37 gear ratio, 3.73 rear axle ratio, 8.84 final drive ratio, 3,000rpm = 26mph, 4,000rpm = 35mph
3rd gear: 1.49 gear ratio, 3.73 rear axle ratio, 5.56 final drive ratio, 3,000rpm = 42mph, 4,000rpm = 56mph

If I shift in the same manner and speed as I did with the ICE, I can feel a very slight drag on the synchros and the shift is smooth. If I take just a 1/2 to 1 second longeer to wait for the motor to slow slightly, the trans falls into gear completely smooth without any drag on the synchros whatsoever.

As far as safety, I can somewhat agree that not having a clutch could be an issue in a runaway, but you're correct that freewheeling a runaway is going to absolutely destruct the motor and probably the coupler and trans input shaft also. My system has three methods of disconnect. The secondary contactor disengages at throttle-off, the primary contactor disengages at key-off, and I mounted an emergency e-stop mushroom style palmswitch/panic button on the dash that kills both the primary and secondary contactor coils if activated. I don't know if I could physically force the transmission into neutral under full power; I really don't want to ever have to try.
Great post, Carroll :)
 
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