rj
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| posted on 27/11/06 at 01:02 PM |
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electric reverse
Hi, my car build is progressing nicely, and i wish to have electric reverse,I was thinking of just using a car starter motor engaging with a gear
fixed between prop & diff, diff is bolted to chassis.
Before spending many hours doing this,I thought I would ask to see who else has done it, and does it work,if it does what starter was used,what gear
diameter etc
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BenB
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| posted on 27/11/06 at 02:19 PM |
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You really need some kind of engagement / disengagment mechanism. Otherwise you'll destroy that starter motor... IE it is designed to run turn
quite slowly when working, if you spin it up really fast passively you'll just destroy it 
Choice of starter motor isn't that important- I know of people who have used bike starters, some use car starters... Whichever you've got
handy. Bike starters are often lighter....
Ring gear mechanism clamped between prop and diff is usual. Often people have the starter on a slider mechanism as their engagement / disengagement.
If you choise this one, as you slide the starter motor into place you will probably have to gently blip the reverse button to get it to mesh to
the ring gear...
Electric reverse mechs tend to be quite slow (slow walking pace) and they put a bit of drain on the battery (especially as you'll be idling so
the alternator won't be working). On a flywheel-less BEC keeping the rpm at a set revs whilst in neutral and travelling backwards is difficult.
If I was using a reverse I'd try and make up a throttle bypass air valve to raise the RPM to 3k when reverse is engaged to try and
compensate.... Otherwise you can kill your battery...
CEC it's less of a problem. Often chunkier batteries and easier to give it a tickle on the throttle to up the revs...
Ben
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rj
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| posted on 27/11/06 at 04:48 PM |
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thanks for that ben,I was thinking of using the starters own solenoid to engage the pinion, so it wont be in mesh except when reversing
I was also thinking of running the bike engine at a high/very high ! tickover speed to generate enough amps to run the reverse motor,hopefully this
will mean I can just use a bike battery
I think that the gear on the diff will be quite limited for size,i wondered if that will be a problem ?
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BenB
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| posted on 27/11/06 at 05:48 PM |
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Yup. Getting the right size ring gear (ie within the limited space available) is the main problem...
Can't think why using the solenoid wouldn't work- I'll check with my bro. He's made a couple of homebrew reverse mechs (one
for Fury, one for a Ginetta) and he's researched it all to ridiculous levels!
You can get them laser cut to custom sizes if necessary....
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ruskino80
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| posted on 27/11/06 at 07:21 PM |
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why bother-i have never had reverse and it has posed no problems at all!!
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