Cita
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| posted on 18/4/04 at 05:51 AM |
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Differential
Hi,i'm a new so expect this question to be completely stupid...but i'm willing to learn.A few weeks ago i started the build of a light
weight formula style hillclimb car based on the locost principle ( what ever that may be).I got hold of a Mercedes 190 diff with halfshafts,disc
brakes etc...witch i'd like to couple to a Honda 500 cc dirtbike engine.
The problem is that looking at the diff's flange it need to be turned clockwise in order to turn the wheels forward.My engine has it's
output shaft on the right hand side meaning the output sprocket turns anti clockwise.
The easiest solution IMHO offcourse is to turn the diff upside down (god bless those with a simple mind) et voila, problem solved.
Since this car wil be running for short periods of time only and with moderate power feeded into the diff,perhaps,just perhaps i can get away with
this aldo i have very strong doubts about it.
Any help concerning the use of a upside down used diff is appreciated.
Thanks
Gilbert
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Mark Allanson
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| posted on 18/4/04 at 10:32 AM |
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I am no expert on diffs, but there was talk on here a while ago about the pinion acting on a different parts of the crownwheel if run upside down. In
your application (offroad) I would have thought it would no be a problem, as long as the mileage is not high, and you are willing to change the diff
if it breaks (make it easy to get out!)
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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NS Dev
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| posted on 18/4/04 at 10:47 AM |
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Other than the oil supply, the differential doesn't know whether it's upside-down or not. The pinion is still turning the same way. If the
input direction to the axle was reversed then the issue of loading different parts of the pinion would become greater. In your case it will be fine as
long as you sort the oil breather for the diff out so it doesn't all leak out!
Ultima kit cars, as well as many other kit cars, use an upside-down porsche 911 transaxle with no ill-effects at all for normal mileages (40,000 miles
with no problem anyway) and in the Ultima that is with a 500hp V8 so I don't think you will have a problem.
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britishtrident
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| posted on 18/4/04 at 03:56 PM |
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One problem is the propshaft centre line is higher not so bit a problem with IRS as a live axle.
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Cita
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| posted on 18/4/04 at 04:56 PM |
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Thanks for the reply's guys.Dave has a point when he mention the fact that the diff turns in the opposite direction from normal in my case.
I have not sorted out yet if i gonna use a short chain drive or a adaptor flange unit but i guess that the chain allows more innacuracy (one of my
habbits!) than the direct adaptor plate.
As soon as the frame is in a showable (is this English ? )state than i will try to post some pictures about my Gocost ( a cross between a locost and
an oversized gokart)
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NS Dev
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| posted on 18/4/04 at 09:47 PM |
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quote:
Originally posted by Dave Ashurst
NSDev
That sounds like excellent news, but would the pinion actually still be turning the same way in Cita's case?
If it IS then that's OK as you say, but in Cita's case I think the pinion actually rotates the opposite way to normal.
If so then the helical gearing on the pinion and crownwheel will reverse the forces on the thrust bearings won't it? Perhaps that's OK
if the diff is designed for big engine braking forces? But perhaps it's not.
If so then those counter-rotating, front wheel drive, honda multivalve car engines might start to look more attractive.
As Mark says, I'd be tempted to give it a go anyway. Let us know what happens and good luck!
Meanwhile I'm going to have a look at Ultima's set up.
regards
Dave
[Edited on 18/4/04 by Dave Ashurst]
Oh sh1t, yes, I must apologise profusely, you are quite correct Dave, and I now feel like a complete idiot for not reading the post properly!!! You
are quite right, it is the wrong way, and yes, I wouldn't want to load it in reverse like that. I do not know what that would do for the
bearings or the oil film on the pinion teeth/crownwheel teeth.
The Ultima setup is turning the diff upside down but also 180 degrees around too so the pinion is still going the "right" way.
I got all muddled, and I must apologise again, sorry!
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Cita
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| posted on 19/4/04 at 04:48 PM |
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If the Ultima uses the diff upside but also 180 degree turned does this mean that the diffs output shaft flange is pointing backwards or am i
completely lost on this?
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NS Dev
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| posted on 19/4/04 at 05:06 PM |
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Yes and No!! It uses a Porsche 911 transaxle (with diff in it obviously) and the Porsche is rear engined, so the input normally points backwards, they
flip it over and turn it 180 degrees so it points forwards and connects to the mid-mounted chevy v8! I got myself all muddled too when I replied, must
apologise again for my incorrect answer!
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Cita
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| posted on 19/4/04 at 05:22 PM |
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Thanks NSDev, now i understand.Didn't know they used the Porsche diff.were the engine is placed "behind" the diff.It's all
clear to me now.
So to get back to my original post,it is not advisable to use the diff turning against it's original direction?
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NS Dev
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| posted on 19/4/04 at 05:27 PM |
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No, after all that and now I finally understand the question!! I would not recommend it as the "spiral bevel" type gear is designed to be
loaded in one direction, and you would be loading it in the wrong direction, bearing and oil film on the gears would be two issues I would worry about
if it were my car. Have you got any photographs of how the engine is mounted etc?
I race in autograss racing in the UK which is dirt oval racing and a lot of people use bike engines (though mine is car engine based), maybe some help
there??
[Edited on 19/4/04 by NS Dev]
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NS Dev
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| posted on 19/4/04 at 06:18 PM |
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Just added some pics of my autograss car to my photo archive. Not a locost but has similarities, perhaps should have cleaned it a bit more first
though (although you should have seen it after the race....correction, you couln't see it after the race!!!)
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Cita
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| posted on 19/4/04 at 06:21 PM |
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I will post pictures as soon as possible but the general layout is:engine is mounted in a craddle wich will be connected to the diff via a adaptor
flange or i can mount the engine a liitle bit beneath the diff and use a short chain.
The main problem is that my output shaft of the engine is on "the wrong side".meaning to the righthand side when in its original bike
frame position
I really have no clue how to solve the diff problem other than using some sort of gears.
ANY help is most welcome.
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Cita
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| posted on 19/4/04 at 06:26 PM |
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That's a hell of a nice car NS Dev!!Did you built this completely yourself?
Especially like the rear suspension!
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NS Dev
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| posted on 19/4/04 at 06:30 PM |
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Yes, completely self built, far from perfect but I cannot drive well enough to get the best from it yet! The rear suspension is trailing arm, as used
by most cars in my classes of racing, and is designed to keep the wheels quite upright and allow the car to "sit down" off the start line
and grip on the dirt surface.
The engine in the Vauxhall 16v XE engine which I keep ranting on about in the engines section, this one makes around 200hp.
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JoelP
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| posted on 19/4/04 at 08:05 PM |
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whats the can of stella in piccy 3 for?! 
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NS Dev
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| posted on 19/4/04 at 08:13 PM |
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Drinking before the race
No, it's just the catch pot for the crankcase breather, doesn't get much in it but it stops it going on the floor!
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Cita
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| posted on 20/4/04 at 07:07 PM |
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It's not important how much you can get IN a Stella can,but how much you can get OUT of it (beer that is).This is probably one of the two things
that we Belgians are still good in,making beer is the one thing and the other... i'm not sure about it but it has to be producing a massive
hangover or...messing things up!
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NS Dev
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| posted on 21/4/04 at 08:08 PM |
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yes, the old stella does give a bit of brain ache in the morning!! Does a world of good to your racing abilities next day!!
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ady8077
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| posted on 21/4/04 at 08:19 PM |
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Hi all
Does anyone no which direction the front diff off a sierra 4x4 turns?
Adrian
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Cita
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| posted on 22/4/04 at 08:05 PM |
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Yes NS Dev,Stella does give you a bit of a brain ache the next day,only the less brain one have....
Have giving that diff problem a good thought and decided to rebuild it to a chain drive.
Tonight i have dismanteled the diff and everything seems to be in excelent condition (must have been cause the poor bastard who bought that Mercedes
in the first place plunked down a lot of money for an "average" car and some long gone prestige).
At first glance i dont see to many problems to the rebuild except for the ratio.I would like to keep the diff housing as intact as possible
strenghtwise so the sprocket replacing the crownwheel will be of modest diameter i guess.Only hope that the smaller wheels,compared to the rather huge
rear wheel of a dirtbike,compensate for the marginal ratio between the engine sprocket and the diff sprocket.
I have an idea of using heavy duty SS steel door hinges to replace the metalastic bushes for the suspension.Dont know if it will work but i guess
it's worth trying giving the low price these hinges cost.
Constructive (and not so constructive) critisism is allways welcome.
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