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Guest Message by DevFuse

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Gear reduction units...

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7 replies to this topic

#1 StormTrooper


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Posted 20 September 2003 - 03:12 AM

Talked to a subie gyrocopter engine builder from Marysville Cali through e-mail, and he says that his Gear Reduction Boxes are compatable with an automotive tranny. So there are kits available for lower gears via a setup that would bolt up between the motor and trans...

this would involve moving the engine back, id assume...

what does 2.18 to 1 compute to when reduction is ran from in the front of the driveline?

unfortunatly they cost a grip...just curious how significant the gearing for off road purposes would be improved..this could do wonders for someone's buggy or hatch!

#2 GeneralDisorder


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Posted 20 September 2003 - 09:15 AM

Sounds more like it would move the tranny back... or the engine forward. Doing that before the tranny would make the car a tractor I would think. Basically would break your RPM's in half, so to do 75 in my wagon, I would have to run 4th gear at 8000 RPM's. Needless to say it would make freeway driving impossible.


#3 JonOfScio



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Posted 20 September 2003 - 09:49 AM

yeah, GD, my hatch does 75 at 4 grand in 4th gear. But unless I need to move quickly or something I just use 5th gear after 55mph.

#4 asavage


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Posted 20 September 2003 - 10:50 AM

Unless I'm mistaken, the GR units they use for aircraft have NO provision for a clutch. Whatcha gonna do?

#5 StormTrooper


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Posted 20 September 2003 - 11:26 AM

yeah, I meant engine foward, not back....

as far as clutch goes, I pretty much figured one would have to stick with a 3sp AT if they wanted to reap the benefits of using a reduction like this...

wow a tractor huh? Be pretty funny to be driving down the highway, and look into a cut cornfield, to see someone's hatch discing a field!!! :banana:

Seriously though, I just threw this out there because I saw a few people on the board fantasize about something like this, and I happened to stumble across someone who actually makes em...

they are availabe for EA81 and Ej22's..

So whose gonna build the next rock crawler??!!!!

#6 bushbasher


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Posted 20 September 2003 - 06:33 PM

The transfer case mod +front diff that mudrat, adam, and others have done has solved that problem, and they can still be driven at highway speeds. Putting a reduction between the engine and tranny would put twice the torque through all the gears too. The next step is some high-angle axles and long travel suspension.

#7 asavage


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Posted 20 September 2003 - 07:03 PM

You can't put a reduction box between the engine and the 3AT's torque converter, 'cuz the TC won't work properly (until you really rev it up). And the 3AT won't shift at the right RPM, you'd be able to use 1st & manually use 2nd (snow mode feature), but never 3rd, it just wouldn't ever upshift.

Talk about a high-stall converter!

RE the tractor thing. There was a time when you could buy a sort of "tractor kit" for a Ford Model T. GR boxes at the rear axles (think of the setup on the pre-68 VW Transporter: same idea), big rims, etc. People found out pretty quickly that you can't put tractor-type loads through a T's frame for very long -- they break. So did everything else. There's a reason why a tractor weighs as much as it does ;)

Same goes with the hatch -- you wouldn't want to try to haul semi-trailer loads behind one, because actually putting that much torque into the hatch's drivetrain (and frame and suspension) for very long will quickly find all the weak parts.

Short bursts is another matter.

The GR units available are designed to let the engine run in its optimum torque range, and keep the prop from overspeed -- the prop tips reaching the speed of sound, which is bad for props. Or, at least, that's what I've heard.

#8 StormTrooper


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Posted 21 September 2003 - 09:06 PM

I was totally kidding about the hatch tractor...i know you couldnt do that.

But the guy who makes them says they go in, someway or another...

look at http://hometown.aol....yro/jsgyros.htm

e-mail him and he'll tell ya how it works

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