spunky
|
 posted on 10/8/04 at 12:46 PM |
|
|
Stupid question in the wrong section
Hi all,
this could be posted in 'running gear' section but is sod all to do with cars.
I understand how a diff works, but will a diff allow wheels to turn in opposite directions while under power?
Try again......
What I'm asking is, does a diff limit the turning circle of a vehicle to one wheel driven and the other static or wll it allow the vehicle to
turn around the center point of the rear axle.
Hope that makes sense.
Many thanks in advance
John
The reckless man may not live as long......
But the cautious man does not live at all.....
|
|
|
|
|
locoboy
|
| posted on 10/8/04 at 01:05 PM |
|
|
lost me 
ATB
Locoboy
|
|
|
ned
|
| posted on 10/8/04 at 01:12 PM |
|
|
I underetand what you're asking, but wouldn't like to hazard a guess ! You must either have a long wheelbase or need a very tight turning
circle for this application..?
Ned.
beware, I've got yellow skin
|
|
|
locoboy
|
| posted on 10/8/04 at 01:14 PM |
|
|
come clean Spunky, what sort of idea have you got doing laps in your head? 
Some insane plan must have prompted this question
ATB
Locoboy
|
|
|
ned
|
| posted on 10/8/04 at 01:25 PM |
|
|
how do those little kybota mini diggers with 4 wheels with tyres on that scrub a lot work?
Ned.
beware, I've got yellow skin
|
|
|
Peteff
|
| posted on 10/8/04 at 02:13 PM |
|
|
They have slewing levers to brake each side independently while the other side still drives, usually by hydraulic wheel motors I think. Some reduction
diffs as used on artic units may do what you are asking.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
|
|
|
heinlein
|
| posted on 10/8/04 at 02:38 PM |
|
|
Almost 30 years ago my cousin had a tractor that had two levers; each one controlled the track on its respective side. You could spin it in its own
length.
But to answer your question I don't think its possible to do with a differential.
When you're lying in the midst of the Afghan plains and the women come out to cut up the remains; just roll to your rifle and blow out your
brains and go to your god like a soldier.
|
|
|
andyps
|
| posted on 10/8/04 at 02:49 PM |
|
|
There is only one way to find out - build a really short wheel base car with a very tight turning circle. I think it maybe would turn both ways but am
not sure. Need more thinking time.
Andy
An expert is someone who knows more and more about less and less
|
|
|
spunky
|
| posted on 10/8/04 at 03:29 PM |
|
|
Thanks fellas for those inconclusive replies
I've given it some more thought and still drawn a blank.
With one wheel locked the other will turn at double speed. If the turning radius was decreased further to less than than wheelbase then on wheel is
required to rotate 'backwards' I can see no reason why this would not simply increase the speed of the opposing wheel proportionately. But
doesn't sound right to have opposite wheel rotation.
Curious innit.
John
The reckless man may not live as long......
But the cautious man does not live at all.....
|
|
|
Viper
|
| posted on 10/8/04 at 04:51 PM |
|
|
Something for robot wars?
|
|
|
spunky
|
| posted on 10/8/04 at 05:32 PM |
|
|
quote:
Originally posted by Viper
Something for robot wars?
You're on the right lines.
I'm actually making preparations for my fancy dress costume for New Year.
Picked up a motorbilty scooter yesterday ready for chopping it up.
A shame really, it has alloy uprights all round, rear live axle with alloy diff and axle, front wishbone suspension and split rim alloy wheels
Oh yeah, if anyone wants to know the answer to the question, I just tried it and yes, the diff allows wheels to turn in opposite directions. So
spinning on the axis is possible.....Yippee
John
The reckless man may not live as long......
But the cautious man does not live at all.....
|
|
|
carcentric
|
| posted on 10/8/04 at 06:30 PM |
|
|
Spunky John -
That sounds right, because when you jack up the rear end of a RWD car with an open diff and spin the propshaft, each drive wheel turns in a different
direction.
That's how I test to see if a donor has a LSD - if it does, both drive wheels turn in the same direction under the circumstances above.
M D "Doc" Nugent
http://www.carcentric.com
|
|
|
Bob C
|
| posted on 10/8/04 at 06:32 PM |
|
|
If the centre of rotation is in he middle of the back axle, there's no way you can make the turn happen under power from the prop, cos in this
case it's impossible to turn the prop! I dare say you can get quite close to it though.
You see what I mean - if the axis is in the middle the inner wheel will go EXACTLY as far backwards as the outer wheel goes forwards. Put another way,
to do it on a trike the front wheel would have to be exactly at 90degrees to the way the back axle's pointing - you ain't going
nowhere!
cheers
Bob
|
|
|
hortimech
|
| posted on 10/8/04 at 06:33 PM |
|
|
ned, the kubota mini diggers with tyres on are actually small tractors fitted with backhoes and loaders. the reason they can turn so fast and tight is
the front axle changes gear as you turn and the front end pulls you round.
Why does everything happen to me
|
|
|
JoelP
|
| posted on 10/8/04 at 09:22 PM |
|
|
it wont work, cos when the wheels are turning in opposite directions at the same speed, the prop isnt turning. If you turn it, you will move forward
or back. However, if you have the equivalent of a FWD bow thruster it would turn...
|
|
|
Stuart Walker
|
| posted on 10/8/04 at 09:48 PM |
|
|
I think it would only work without power (ie. the wheels turning each other - no prop movement), but once the prop has power i reckon it wouldnt work.
Bear in mind this is based on a highly (in)conclusive test with a remote control car and could be wrong...........
|
|
|
spunky
|
| posted on 10/8/04 at 11:31 PM |
|
|
quote:
Originally posted by JoelP
it wont work, cos when the wheels are turning in opposite directions at the same speed, the prop isnt turning. If you turn it, you will move forward
or back. However, if you have the equivalent of a FWD bow thruster it would turn...
Thats what I thought Joel, but it appears to work. the diff internals turn to compensate for the direction and speed differences.
I agree that to spin around the centre the rear axle is probably unlikely as the steering would need to be perpendicular to the driven wheels but you
should get close.
Only one way to find out for sure and thats get building....
john
The reckless man may not live as long......
But the cautious man does not live at all.....
|
|
|
hortimech
|
| posted on 11/8/04 at 12:00 PM |
|
|
to spin around in circle you need two power sources, one wheel goes one way, the other goes the other. try driving a zero turn mower, they are great
fun
Why does everything happen to me
|
|
|
