17 replies to this topic

[cheapracer]

I am looking for a very small differential center, anyone want to nominate what they think is the smallest, mass production one they know?

I just need the action not a crownwheel and pinion so doesn't even have to be automotive....

[cheapracer]

Hmm, after I posted that a 3 wheeled motorcycle arrived outside the offices, one of millions here - doh!

[Kelpiecross]

I am looking for a very small differential center, anyone want to nominate what they think is the smallest, mass production one they know?

I just need the action not a crownwheel and pinion so doesn't even have to be automotive....

Do you mean as small as a diff on a radio controlled car? Some have normal gear-type diffs - not just the ball type.

[cheapracer]

Do you mean as small as a diff on a radio controlled car? Some have normal gear-type diffs - not just the ball type.

Thank you, no - I meant as in a robust unit about the size that will fit into your palm. I didn't consider the model cars as I thought they would be all plastic.

Ball type is no good as I need definite mechanical engagement.

[kikiturbo2]

do you want a limited slip diff or normal one? and for what power?

I have a front diff from a EVO 7/8/9 at home and it is a really nice small unit.. (available in open / torsen / plate configurations)

[cheapracer]

No but thanks. Its for a specific mechanical action and needs to be a basic standard no thrills open type.

I have little doubt one of the 3 wheeler ones here will fit the bill, thanks again.

Oh I think I have found what I want, ride on mower type..

http://www.alibaba.c.../showimage.html

http://www.alibaba.c.../showimage.html

Edited by cheapracer, 17 September 2011 - 07:51.

[Kelpiecross]

No but thanks. Its for a specific mechanical action and needs to be a basic standard no thrills open type.

I have little doubt one of the 3 wheeler ones here will fit the bill, thanks again.

Oh I think I have found what I want, ride on mower type..

http://www.alibaba.c.../showimage.html

http://www.alibaba.c.../showimage.html

What are you aiming to do with your small diff?

[cheapracer]

What are you aiming to do with your small diff?

It's not for a vehicle per se. I need 2 levers to go opposing directions at the same time (linked) for another application.

Further to that does anyone know what you call that action? In this exercise machine for example the arm levers have this action where one goes forward and the other comes back because they are linked... I don't think it's "scissor action"?

[24gerrard]

Reciprocation?

Edited by 24gerrard, 18 September 2011 - 09:27.

[mariner]

For what it is worth the exercise machine is called a cross trainer, or sometimes an elliptical cross trainer as the joint between the horiziontal cranks and the vertical links follows an elliptical motion.

[cheapracer]

Reciprocation?

I heard some thunder earlier but no need for an umbrella I believe.


But no, thank you, "recipricating" implies a back and forth action where I need to describe a singular action on a lever that causes an equal but opposite reaction on another lever similar to the exercise machine's action ie; push the left lever forward and the right lever goes backwards - hmm going to look at definitions of "rocking".

[Tony Matthews]

A Newtonian system?

[MatsNorway]

There are 1/5 scale diffs for rc cars..

Kinda solid.

to small?

Then you have 1/4 scale diffs.




What power/torque values are we speaking of?

the 1/8 scale nitro cars got 2.5-3hp 0 - 100km`t can be over as quickly as in 1.4sec

Edited by MatsNorway, 18 September 2011 - 15:00.

[cheapracer]

What power/torque values are we speaking of?

Good question, halve to work it out i guess but those mower sized diffs 'feel' right.

A Newtonian system?

2 things, the car naming thread isn't this one and I'm not falling for your sneaky way to get your name on my car Mate...

[saudoso]

It's pretty much a reciprocating mechanism I also think. The inertia disk is the crank, the lady steps on the rod and the big diameter of the handle centered movement can be approximated to forward/backward movement

Edited by saudoso, 18 September 2011 - 15:41.

[Tony Matthews]

2 things, the car naming thread isn't this one and I'm not falling for your sneaky way to get your name on my car Mate...

Damn, rumbled...

[bigleagueslider]

But no, thank you, "recipricating" implies a back and forth action where I need to describe a singular action on a lever that causes an equal but opposite reaction on another lever similar to the exercise machine's action ie; push the left lever forward and the right lever goes backwards - hmm going to look at definitions of "rocking".

cheapracer,

You described the kinematic device you need in your post, it is indeed a center fulcrum lever, with end-mounted connecting rods. If the connecting rod geometries are symmetric about the lever fulcrum point at mid-stroke, then I believe you will have fairly balanced forces in the connecting rods.

You don't, however, want a common gear differential. Equal and opposing inputs into a simple gear differential would result in no net motion at the output. Think of a simple gear differential as a mechanical adding machine, with two inputs and one resulting output. If one input is +20rpm and the other input is -20rpm, the resulting output is 0rpm.

hope that was helpful.
slider

[cheapracer]

cheapracer,

You described the kinematic device you need in your post, it is indeed a center fulcrum lever, with end-mounted connecting rods. If the connecting rod geometries are symmetric about the lever fulcrum point at mid-stroke, then I believe you will have fairly balanced forces in the connecting rods.

You don't, however, want a common gear differential. Equal and opposing inputs into a simple gear differential would result in no net motion at the output. Think of a simple gear differential as a mechanical adding machine, with two inputs and one resulting output. If one input is +20rpm and the other input is -20rpm, the resulting output is 0rpm.

hope that was helpful.
slider

I know this much now, it's a class 1 lever. Maybe "reciprocating output center fulcrum mechanism" or "mechanically engaged scissor"?

A differential is perfect actually, the diff's casing will be clamped into place and the axles/side gears turn the planet gears so effecting opposite rotation ie; turn the left axle clockwise and the right axle will turn anti-clockwise or in this case push a vertical lever forward on the left axle and an identical vertical lever on the right axle will move backwards.

Help is always helpful that's why it's called help

Edited by cheapracer, 20 September 2011 - 08:48.