zilspeed
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| posted on 3/8/08 at 12:09 PM |
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El cheapo reverse update. (Long and boring)
Quick summary of where I'm at with this.
Audi diff used in the quattro II system up until around 1994. Has mechanical locking via a release arm powered by an actuator - this is the diff to
use in the tranny tunnel as a reverse box.
Remove the input shaft and extended input housing to leave the bare diff. Cut down the extended housing to provide cover to keep oil etc happy to stay
in 
Having thought about mechanisms for actuating it is now obvious that a purely mechanical system is actually counter intuitive. You would need one
lever to engage reverse and another to engage forward drive. Much too confusing.
For that reason, I have come to the conclusion that electrical actuation via relays actually makes much more sense.
The existing electrical actuator will be used to engage forward drive, another actuator will be used to engage reverse drive. These will be powered
via two relays which will be controlled by a simple switch. The switch will be an on-off toggle which will engage forward, or reverse final drives.
Elegant and simple, I hope.
Actuator states will be such that forward drive defaults to being engaged with no power applied to either actuator. This should lead to more reliable
running of the system.
Reverse drive will involve both actuators being engaged to 1) engage reverse drive and 2) disengage the default state from the forward drive. The
short running times for the reverse circuit will again aid reliability.
So in summary.
1) Switch up, both actuators unpowered. Reverse defaults to off, forward default to on. Car goes forward.
2) Switch down, both actuators powered.
Reverse is engaged, forward is disengaged, car goes in reverse.
That's it.
Nearly forgot.
Output and input shafts.
We want the drive flanges to be the same pattern as the sprocket adaptor for ease of procuring suitable driveshafts.
The diff uses CV joints with 8 bolt fixing bolts.
I will CAD up a pattern for an adapter plate which has countersunk fixings for the existing mounting bolts and has 4 tapped mountings for the 4 bolt
UJ as used in most props. This needn't be any thicker than 12 - 15mm and should be easy to have waterjet cut.
So there we have it.
An electrical actuated, but entirely engine powered reverse mechanism which does not depend on a whining motor on a cog.
Your input appreciated.
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BenB
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| posted on 3/8/08 at 02:33 PM |
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Do you know what the weight penalty is for adding the system?? You'ld hope it wouldn't be too much but some 4*4 mechs are pretty
industrial things...
Sounds very trick though!!!
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aerosam
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| posted on 3/8/08 at 04:02 PM |
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why don't you just add a trap door in the floor so you can reverse flintstone style?
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zilspeed
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| posted on 3/8/08 at 04:38 PM |
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None of this is tricky to do you know.
It's been more difficult to figure out and get to this stage.
P.S. What width of slicks do you reckon you'll need on the front of that car you're building to kill the understeer that V8s gonna
generate.
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