glenn

I've done some searching and found that there are torsional differentials available for the off-road rc cars. Are there any lsd's (clutch or cone type) availabe for on-road nitro rc cars? I'm considering designing one for my thesis but it's pointless if they already make them.

kn7671

For Off-Road RC Cars has been the only application I have seen different types of differentials for. The physical room on off-road models is more than on-road cars since the off-roads are 1/8 scale while on-road are 1/10 scale.

This seems like a good subject, but the ball type differentials on on-road cars are really simple and do the job well. Traction on the track itself for on-road cars is usually not as huge a factor as dirt.

If you have the resources to design such a thing, I would like to see it. I think you will be limited to shaft-drive cars since they have more differential room than belt-drive.

dg2b

There are 1/10th off-road cars also and are not limited to just 1/8th.

You can check Kyosho's website. They have used lsds on their V1RR and Fantom. You can also check Kawahara negative diff. Same concept, slightly different design.

glenn

I checked out kyosho's website and all I found was an "active" differential, which I'm guessing is what you were talking about. Is that a true limited slip differential? I can't really find any writeup on either one. I'm just trying to see if it's worth my time or not. For kawahara the only site I found was some lotus car site that was mostly in Japanese but I saw a pic of their negative differential and on the outside it looks identical to kyosho's. Do you know what they mean by negative differential?

drf

Whenever I have an idea any search on the net to see if I am the first one to have though about that, 99% of the time someone else has already done it. I would say it sounds very interesting and worthwile to have a lsd in your rc.
Even if someone has already done it I would say go for it. I'd think of "they did it, I can do it better"
For waht scale are you looking at?
Also beware of the academics. The like lots of mumbo jumbo stuff in the reports so it will be a bit of pain in the *****. See if you can find enough literature on lsd's to support your design-they just love if you work with something that has already been discussed by other"acknoledged academics".
Are you Undergraduate or Masters level?

glenn

It's an undergrad thesis. I'm going to talk to my prof about this topic and see what he says. I already have a couple of potential designs in mind. You're right there can always be inprovements either in function or cost. For scale I was planning on using 1/10 scale car as a platform.

dg2b

The terms active, lsd, negative, and others are all different terms referring to the same thing. Another term you will hear which refers to the same item is "center force" = centax.

Anyway, the way the negative diff work is that there is an internal clutch within the diff. When power is applied to the unit, the clutch will engage and make the unit a solid diff (positive). Lesser power applied = lesser clutch pressure thereby slip. When there is no power to the unit, it acts like a differential.

Kyosho released the V1RR with an LSD which requires diff oil. Kawahara's negative diff only uses grease. One difference between the LSD and the negative diff is that the LSD does not lock up at a specific RPM, but the negative diff does.

BTW, your doing a thesis for undergrad? Glad I didn't [sm=wink.gif] Let me know if more info is needed.

otterball21

My Feedback: (1)

limited slip in a car is where the pads of a spring loaded mechanism is pressing against the gears to make them have equal amounts of power.. yet when turning a corner.. it still will be able to "slip".... they should lock the differential.. but then that would just make the car drive funny... My bronco had a open differential.... and now I have a posi = limited slip... quite a different.. every time I make a turn now the tires attempt to chirp and grab onto something... good luck on your undergrad thesis.. Man.. I wished my biology teacher would give me a thing to do on RC cars or something..

drf

1/10 is a bit small. Check if you university has a CNC machine to make it, otherwise check any company that could make something like that and ask them for cost(very roughly) have it on hand as you proffesor might be conserned of cost. They dont usually give a lot for undergrad level. Also be aware. He might say ok and then tell you to do it a complete simulation of it (probably Ansys or Abaqus) which is a REAL pain in the *****. It will take you a lot of time epsecially if you are not very good with computers and grinchy software. If you complete the simulation he may say that is enough so you wont need implementation which sucks as you wont get to have it in your car. Just check it out before hand so you wont have and problems (I talk from experience)
I will definatelly want to see what you've come up with, it really sounds interesting. Keep us posted!!!

glenn

Thanks for the replies, I was checking out the diff in my friends hpi rs4 (I think) and it does seem a little tight for space in the 1/10 scale but at the moment the scale isn't really a concearn. We have some cnc machines at my school but I can't remember what we have (haven't seen it in a couple of years). I won't have to do it on ansys that's more of a finite element program, I'll model it on adams (just like ansys but dynamic modeling) or just draw it up on autocad.