The Reasons why Automatic Gearboxes WILL Work with EV's & how to do it.. - DIY Electric Car Forums
Go Back  

DIY Electric Car Forums > EV Conversions and Builds > Technical Discussion

Register Blogs FAQ Members List Social Groups Calendar Search Today's Posts Mark Forums Read

Thread Tools Display Modes
Prev Previous Post   Next Post Next
Old 03-13-2009, 01:21 PM
Big-Foot's Avatar
Big-Foot Big-Foot is offline
Join Date: Jun 2008
Location: Minneapolis, MN
Posts: 39
Big-Foot is on a distinguished road
Arrow The Reasons why Automatic Gearboxes WILL Work with EV's & how to do it..

Who am I?
A gearhead like you are. I now make a living in technology but am a certified journeyman mechanic as well. I'm in my mid-fifties and old enough to know when I'm beat and how to capitalize on other peoples work as well as their mistakes. I currently do racecar fabrication and I drive as well during those hours that Corp. America does not have her hooks in me. Like many gearheads, I have more projects than time.. When I crossed the boundary into my 50's I realized that I was burning hours on the sofa in front of the idiot box that I'd never recover. So I guess now I've traded seats and now spend at least some of that time in front of my PC whilst enriching myself on the Internet. During my years turning wrenches - I've been through many automatic transmissions. Of course I was baptised by fire when thrown into the deep end with a Turbo-400 from a pickup truck was assigned to me. (worked like a charm thank you).. I've a thorough understanding of these myterious slush boxes and have grown to both love and hate each one of them equally.
I've had a dream since I was 10 years old to build a series hybrid. Yes over 4.5 decades ago. It was then that my Grand Pa (a brilliant engineer) and I sat down at the rail yards and he taught me how the "new" Diesel Locomotives worked.
It was that principle that I wanted to use (in essence) in the creation of my own EV. Start out building and refining the car as an EV and adding Waste-oil diesel generator to the mix for a range extender.
I have my own Mill and Lathe and, of course, welders.
Enough about me..

I've read through nearly 30 pages of YES YOU CAN and NO YOU CAN'T on the "other" thread.. I've addressed some of those issues here (if you can stand reading that much)..

I'd ask one thing of the participants to this thread -
Please keep on topic. Those of you that want to say how rediculous the idea is - please see other thread.

On with the show....
I see many people touting the line - "Well if you wanted a standard - why didn't you start out with one, that's what you're making your automatic into anyways!" Guys - read the PROs below - that's why..

PROs -
- Automatic is lighter
- Automatic does have "ParK" selector - Go ahead and use the parking brake on a Northern car that's 15 years old - You'll be calling a tow to the shop to un-freeze your rusted cables.
- Automatics are less intimidating to people that have never driven a std
- Many really good prospective donors have been passed up due to their transmission
- Conversion to a stick requires not only the transmission but retrofitting the shifter from auto to std.

Addressing the Green-ness -
- Automatic trans fluid can be recycled along with regular motor oil.
- ATF can be burned for heat very efficiently with super low emissions (it's done frequently up north here).
- Volume of ATF required is dramatically reduced over what's required with a torque convertor.
- Fire potential of the ATF? yes it will burn but you can pour it on a hot exhaust manifold and it will not ignite. It needs to be vaporized first just like diesel fuel or gasoline for that matter. I also think that the potential for fire and explosion is far greater from batteries not put inside of protective casings with crush-zones around them.

Various Notes made during the consumption of the "other" thread -
- Idling the traction motor to maintain pressure is out of the question in my estimation. Keep reading for more..
- Pressure leakage internally is minimal with a transmission in good condition. I've seen a transmission maintain pressure for as long as 30 minutes.
- Slippage on start-up - I don't think this is as big of a problem as some have stated it to be. Point in fact, you do want "some" slippage between shifts and startup due to the high levels of torque in the electric motor at lower RPM. Slippage and the torque convertor (not needed here) are where the vast majority of heat is created in an automatic trans.
- Most transmissions made since 1984 are controlled by the ECU or ETC (I-E Electronically controlled).
The interface to control it can be made quite simply since the actual control inputs to the transmission are binary (on or off). I would suggest that shifting of the transmission still be kept manual with a 4 positions controlled by the shifter. 2nd gear, Neutral, 4th gear (highest 1:1 rather than an OD) and Reverse. If you want to retain fully automatic controls, you could do that as well but with a higher degree of complexity.

If you have a transmission that's a bit of an internal bleeder - you could either overhaul it with new seals and gaskets or add an external accumulator. The Accumulator would have a low pressure switch to engage external pump motor to build pressure to a specific level (40 PSI would be enough). Depending upon the weight of the vehicle, you'll need between 40 and 100 PSI to keep clutch packs engaged without slipping. If you want to hot-rod it, you better be looking for pressures double that.

Speaking of Clutch Packs - I don't know of any automatic transmission shipped in a car that has bands any longer. They all use clutch packs now days. Clutch packs have far more friction / surface area than do bands so they require less pressure to operate properly.

Regeneration: Yes, the wheels will backfeed torque through the transmission to capitalize on Regen if using the AC drive system and appropriate controller(s).

Additional issues to be taken into consideration -
The input shaft of the standard transmission locates between the Pilot bearing and the front bearing of the transmission. This would have to be taken into consideration while making an adapter. This noted - the adapter will need to drive the pump of the transmission and be locked to the input shaft of the trans.

Let's have fun!
Regards - Randy
GT40 Replica in progress

Last edited by Big-Foot; 03-13-2009 at 07:22 PM. Reason: Cleaned up some Schpellink errors and punktiation
Reply With Quote

Share or Bookmark this

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Support DIY Electric Car

All times are GMT -6. The time now is 04:23 AM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Ad Management by RedTyger