differential problem

[Stephen Provoost]

I'm trying to make an Unimog with differential lock.

I have built the back wheelbase with a pneumatick differential lock on a 24th clutch (see picture) To go to the motor I used an 16th gear and a black 12th gear on the same axle, connected to the 16th side of the clutch. with the black 12th gear I made a 90° corner so I have an axle to go to the motor. (hopefully you understand :p)

in the front I haven't figured out yet how i can make a differential lock so I used the original Unimog wheel base with this gear clutch:

when I attach the back wheel base to the Unimog the back wheels are faster/slower than the front wheels. I've searched for a solution but I can't find one.

Thank you in advance

Stephen

[timslegos]

The wheels travel at different speeds because you used different gear reductions between the back and the front axle.

hope this helps

tim

[Stephen Provoost]

The wheels travel at different speeds because you used different gear reductions between the back and the front axle.

hope this helps

tim

I know, but I can't figure out how I can fix it.

[captainmib]

As i understand this correct, the gears you used are different

so, the front gears are bigger than the back gears. A 12tooth gear will run faster then a 20tooth gear on the same axe (well, at least the outcome will)

If you want to run them at equal speeds, you will need to use the same differential, and at least the same gear combination.

So now you have in the back, a 12tooth gear powering a 16 tooth

And at front, a 20tooth gear powering a 28tooth differential

So i think there lies the problem

Hope you understand (hard to think and explain it in words...)

[Stephen Provoost]

As i understand this correct, the gears you used are different

so, the front gears are bigger than the back gears. A 12tooth gear will run faster then a 20tooth gear on the same axe (well, at least the outcome will)

If you want to run them at equal speeds, you will need to use the same differential, and at least the same gear combination.

So now you have in the back, a 12tooth gear powering a 16 tooth

And at front, a 20tooth gear powering a 28tooth differential

So i think there lies the problem

Hope you understand (hard to think and explain it in words...)

I understand, but the 16th differential is 1 stud wider than the 28th differential. it's difficult to make it fit in the front wheel base. In fact, I would also want to have a differential lock in it.

I've tried different times to make one, but then I have a problem with the steering.

[Alasdair Ryan]

I don't have a physical solution how ever you ccould try sariel's calculator.

Gear Calculator

[locoworks]

why not make a second narrower diff for the rear with the same gearing??

[trekman]

You can use a different size of differential on the front and rear axles. The important matter is that this should all be connected to a central differential. This will revolve to "make up the difference". As I understand it, the engine on the MOG is connected to this central differential. However, if you put a differential lock on this central diff, then the complete drive train would "bind up" due to the different gear rations.

It is the same principal which is used in modern agricultural tractors, where the front wheels are smaller than the rear. Even with variations in tyre wear, the wheels do not bind up because the engine and gear box feed a central diff, which inturn distributes the power to where it is needed.

Proper 4WD vehicles do need a central diff, as if all wheels are gripping when going around a tight corner, then they are all rotating at different speeds.

I hope this makes sense.

[locoworks]

You can use a different size of differential on the front and rear axles. The important matter is that this should all be connected to a central differential. This will revolve to "make up the difference". As I understand it, the engine on the MOG is connected to this central differential. However, if you put a differential lock on this central diff, then the complete drive train would "bind up" due to the different gear rations.

It is the same principal which is used in modern agricultural tractors, where the front wheels are smaller than the rear. Even with variations in tyre wear, the wheels do not bind up because the engine and gear box feed a central diff, which inturn distributes the power to where it is needed.

Proper 4WD vehicles do need a central diff, as if all wheels are gripping when going around a tight corner, then they are all rotating at different speeds.

I hope this makes sense.

in theory things would bind up, but in reality the wheels would just slip slightly. the rear axle on 99% of quads is 'live', like a go kart, and it just means there is some skating/slipping on tighter corners. the knack to turning sharply at slower speeds is to shift your weight to the outer edge so the inner wheel can slip more easily. it does put more strain on the motor and driveshafts, but they are built to take it. with tractors as you say there is a diff front to rear that needs to spin, but quite a few more modern tractors actually have the same size wheels all round so any central diff just needs to be limited slip.