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Old 05-24-2008, 10:21 PM
mof4000 mof4000 is offline
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Default explain clutchless shifting

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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Old 05-24-2008, 11:24 PM
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Default Re: explain clutchless shifting

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Originally Posted by mof4000 View Post
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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Old 05-25-2008, 05:57 AM
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Default Re: explain clutchless shifting

Quote:
Originally Posted by mof4000 View Post
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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Old 05-25-2008, 06:10 AM
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Default Re: explain clutchless shifting

Excellent explanation. Matt, can we get this moved into the Wiki area?

ga2500ev
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Old 05-25-2008, 07:28 AM
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Default Re: explain clutchless shifting

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Originally Posted by ga2500ev View Post
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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Old 05-25-2008, 08:00 AM
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Default Re: explain clutchless shifting

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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Old 05-26-2008, 02:51 AM
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Default Re: explain clutchless shifting

Supplemented article submitted to the wiki
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Old 05-26-2008, 06:18 AM
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Thumbs up Re: explain clutchless shifting

Excellent, the wiki is starting to work like I've wanted it to all along!
I knew it would pay off, thanks DVR
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Old 05-26-2008, 07:08 AM
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Default Re: explain clutchless shifting

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.
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Old 05-26-2008, 08:42 AM
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Default Re: explain clutchless shifting

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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