DIFFERENT differentials - do you beg to differ?

[Legacy555]

Originally Posted by Gayo

CR2 : I built my car with the Desert Truck gear diff. Franckly I found the car bad, a bit twitchy on carpet and hopelessly understeery on slippy indoor floor. Again I sold the car quickly but I'm afraid all the problems came from the gear diff. It was also badly made with very soft outdrives, not something I would recommend to anyone.

Agreed on the soft outdrives, but I've actually found the gear diff to be better than the ball diff on carpet. I use the desert truck diff with 35wt shock oil in it. With the ball diff, I was suffering through a high speed hairpin where the inside wheel was getting light on the exit and I was loosing a bit of drive. I put the gear diff in and although the car's steering does seem more dosile I find that you can hang onto a huge amount of speed through the corner and the traction out of the hairpin is almost like a 4wd. I'd recommend trying it, but we're not talking a huge difference, just that extra couple of %.

[Col]

Originally Posted by SHY

This makes me think of front one-ways for 4WD. When I started with 1:10 OR a few years ago, I got the impression that everyone used them. It was simply faster.

But when I finally tried with a front diff everything went way better for myself! Much easier to control, and I really cannot say that I got more steering from the one-way either. And MUCH better in the air of course.

It's not always a good idea to copy the set-up from the very best drivers... unless you have out of this world hand-eye coordination, an easy to drive car is always faster on average!

Originally Posted by jimmy

I was talking to someone this week about oneways - and they made a point I'd not considered and that's just the sheer power and speed of the cars might be too much for a one way now. A lot of drivers I knew running one-ways in years gone by have stopped running them.

I was under the impression that we simply didn't need them anymore due to better geometry built into the more modern cars. Everybody ran a one way in their xx4 to give them better initial turn into the corner and made do with rear wheel braking, whereas with (for example) the B44 has far superior steering built in that a diff is faster due to later braking? That's how I see it, anyway!

[SlowOne]

Originally Posted by mark christopher

10th and 8th ic run then... so they should not be weak?

It's a question of how the power is made up, not the absolute power.

Power = torque x revs. Strength of the system is a function of torque. Gas cars get their power through revs, so their systems can be smaller than electric cars, who get their power through torque. It doesn't follow that a system that works in a gas car will work in an electric car.

A Veyron has twice the power of a 38 tonner, but if you put the driveshaft from a Veyron in a Volvo truck, the Volvo would snap it with one lift of the clutch! All that luvverly torque...!

This is a great thread, full of interesting information. One thing I would be interested in is how you guys measure the torque limiting capability of the various diffs, and how you measure the percentage of lock-up. If this area is well understood, you'll be making good progress, and I'd love to apply your calcs to a 12th diff!

As for Torsen diffs, I doubt they could be engineered into the space provided. However, a smaller version of the Ferguson fluid clutch diff should be possible - imagine a Losi Hydra slipper scaled down and popped in a diff and you get the idea. A clutch-based LSD would also be possible - imagine a PTFE slipper clutch popped in the diff to give you adjustable amounts of limited slip.

If Cecil Schumacher is still up for a challenge, he could make a second living with a proper LSD for On- and Off-Road!!

[Richard Lowe]

Originally Posted by SlowOne

Power = torque x revs. Strength of the system is a function of torque. Gas cars get their power through revs, so their systems can be smaller than electric cars, who get their power through torque. It doesn't follow that a system that works in a gas car will work in an electric car.

Remember the diff is at the slowest rotating part of the drivetrain, 1:1 with the wheels, and therefore at the highest torque point in the car. If an electric car has equal sized wheels and power to a nitro the overall load will be about the same I'd imagine

I'd love to be able to run a one-way diff in 4wd, I'm sure I'd be faster over a single lap - but that's the problem. There's a much bigger chance I'll make a mistake on big stops into slow corners. Also a one-way has a bit of a mind of it's own accelerating through bumps in a shaft drive car, less of an issue on those rubber band cars

[Apricot Slice]

A 10th scale one of these couldnt be that hard to make.

[SHY]

Originally Posted by Jan Larsen

Precisely. The biggest problem with one-ways today is the inability to brake. I tried one in my Tamiya 511 on a big outdoor track. At the end of the 50m, 105km/h straight (we had a speed gun) there was a hairpin. With the oneway I had to brake almost 20 meters before. With the diff I could get that down to 5 meters and 4 tenths on the laptime. Its the sheer amount of speed we carry towards the corner that dictates the need for brakes and the main reason oneways arent used anymore, at least not in the faster classes.

Whaaaaaaaaat!!! You're saying a 1:10 OR car does 105 km/h on the straight???

I'm an experienced 1:8 TR driver, which is the fasted RC class. They do approx 110 km/h on the straight, and that's with super wide sponge tires, a 2-speed and a combustion engine doing 50.000 revs/min...

I know touring cars are faster now with brushless and Lipo, and can show equal or better laptimes than 200mm. But a 1:10 OR being as fast on the straight as a 1:8 TR... sceptical...

Very interesting about the braking!

[Bagman]

I do know that I would pay good money to anyone able to put Durango diffs in my spare FS2. PM me if you are that man.

[SHY]

Originally Posted by Apricot Slice

A 10th scale one of these couldnt be that hard to make.

Cool!

As I understand there's a guy in Germany that has made something like this for his B4- which works very well! But he wants to keep it a secret it seemed...

[SHY]

Originally Posted by Bagman

I do know that I would pay good money to anyone able to put Durango diffs in my spare FS2. PM me if you are that man.

Search and you'll find a tread about that on this forum. I think they were a direct fit vs. the B44 where you need some serious equipment in order to do the conversion...

And remember to order replacement Kyosho O-rings (JE Spares carry them)

Can those of you that know 1:8 OR list all the types of diff existing for those cars? Plus give a quick explanation of the "felt difference"?
-regular diff
-Torsen diff
-Fiorini diff?
...

[dodgydiy]

have been messing with a plated diff, only at early stages really, no friction plates as in a full size diff, just relying on the viscosity of the sillicon oil to provide the limited slip effect, how it compares i cant tell you as it hasnt been put in a car yet, but it feels when rotated to lock up harder than just oil and gears under pressure

[dodgydiy]

have a look at the quaife ATB differential, that would be easy enough to minaturise, they work well too, ond mugen 1/8 diffs were laid out like this but not with helical gears

[Hog]

Originally Posted by SlowOne

However, a smaller version of the Ferguson fluid clutch diff should be possible - imagine a Losi Hydra slipper scaled down and popped in a diff and you get the idea.

Didn't Ford try some of its Rally and Rallycross Capri's from the 70's era with Ferguson diffs and they were notoriously haphazard? Understeer one moment, oversteer the next - that's why you only see photos of them sideways as it was the best way to overcome it.

[Razer]

Originally Posted by Hog

Didn't Ford try some of its Rally and Rallycross Capri's from the 70's era with Ferguson diffs and they were notoriously haphazard? Understeer one moment, oversteer the next - that's why you only see photos of them sideways as it was the best way to overcome it.

I don't know how this compares to the Viscous LSD's that came with the Nissan S13-S14 200SX and my old Mazda RX7, but I remember them as totally horrible. As you mention with the Capris, it was oversteer/understeer/alloversteer/andtowardsthetreessteer in my RX7 as well....

I'm very skeptical towards a fluid based LSD, as I can't really see how that will deliver the precision we want in the size we demand.

Of course, I do not know what technology active differentials from WRC 5(?) years back were based on, but in all my experience, a purely mechanical diff that can be preset as you like it, is a lot more predictable than any viscous and oil based solution. At least with available technology to be put in a 10th scale car

But then again, I'm not familiar with all options, and I'm not an engineer

[Apricot Slice]

[SlowOne]

I had a couple of FF diffs in my Sierra XR4x4, and they were excellent.

Any of these diffs can be scaled to fit into a model, that's the easy bit. What you can't scale is the Laws of Physics, and they start to give different results when things get bigger and smaller. Those results don't always mimic in a model car what is experienced in a full-size car. The clutch-style LSD might not work correctly when the area on the clutch plates gets to be so small, for example. An example of this is the size of dampers we use. If a TC damper were scaled up to a full-size touring car, it would be so big it wouldn't fit in the space provided, but if the touring car one was scaled down, it would have so little fluid and movement it wouldn't work at all in a TC!

That's the challenge, finding a solution that does what you want it to do. Simply looking to full size and trying to scale it is probably not what is needed. Something different is likely to succeed IMHO.

[Apricot Slice]

Originally Posted by SlowOne

I had a couple of FF diffs in my Sierra XR4x4, and they were excellent.

Any of these diffs can be scaled to fit into a model, that's the easy bit. What you can't scale is the Laws of Physics, and they start to give different results when things get bigger and smaller. Those results don't always mimic in a model car what is experienced in a full-size car. The clutch-style LSD might not work correctly when the area on the clutch plates gets to be so small, for example. An example of this is the size of dampers we use. If a TC damper were scaled up to a full-size touring car, it would be so big it wouldn't fit in the space provided, but if the touring car one was scaled down, it would have so little fluid and movement it wouldn't work at all in a TC!

That's the challenge, finding a solution that does what you want it to do. Simply looking to full size and trying to scale it is probably not what is needed. Something different is likely to succeed IMHO.

Have found out about the scale/physics thing first hand building shocks. (that project is still alive. been hibernating.)
Was going to have a shot at making some durable diffs out of grooved race way thrust bearings but this LSD thing has got the old coconut thinking.

one daft idea was to have a cog on each outdrive meshing into an idler and then to another cog that carries a slipper linking each side.
It was the only manufacturable way within my means to do it as far as last nights thinking was concerned.
Probably take up too much space and too much rotating mass.

[Razer]

Fun fact: My latest ball diff did about 350 laps on Thursday and 440 on saturday, on carpet, and it still feels brand new;-)

Also, the B-fast stuff gets a lot of good words, I'll be trying that soon...

[SHY]

Originally Posted by SlowOne

I had a couple of FF diffs in my Sierra XR4x4, and they were excellent.

Any of these diffs can be scaled to fit into a model, that's the easy bit. What you can't scale is the Laws of Physics, and they start to give different results when things get bigger and smaller. Those results don't always mimic in a model car what is experienced in a full-size car. The clutch-style LSD might not work correctly when the area on the clutch plates gets to be so small, for example. An example of this is the size of dampers we use. If a TC damper were scaled up to a full-size touring car, it would be so big it wouldn't fit in the space provided, but if the touring car one was scaled down, it would have so little fluid and movement it wouldn't work at all in a TC!

That's the challenge, finding a solution that does what you want it to do. Simply looking to full size and trying to scale it is probably not what is needed. Something different is likely to succeed IMHO.

Indeed! This was why Team Associated were so successful from the get go! They designed their RC cars as purely RC cars with new ideas, and not trying to downscale a 1:1 car Those who did try to downscale 1:1 car more than anything else ended up with way too complex solutions, and WAY WAY(!!!) too heavy cars!

We also need to remember the INSANELY big jumps our cars face! Only thing that slightly resembles an upscaled RC as I can think of right now are those Paris-Dakar buggies. They have very long suspension travel and can jump like a kangaroo

Originally Posted by Apricot Slice

one daft idea was to have a cog on each outdrive meshing into an idler and then to another cog that carries a slipper linking each side. It was the only manufacturable way within my means to do it as far as last nights thinking was concerned. Probably take up too much space and too much rotating mass.

I'm no engineer, but that looks like a simple and good solution to me!!!

Originally Posted by Razer

Fun fact: My latest ball diff did about 350 laps on Thursday and 440 on saturday, on carpet, and it still feels brand new;-)

Also, the B-fast stuff gets a lot of good words, I'll be trying that soon...

B-fast stuff???

--------------------------------

But guys, have you all read about this?
http://www.oople.com/rc/photos/euros2010/day2/

Georg Kotzinger from Germany was running a pretty standard looking Associated B4.1 buggy - but we got a tip off about his unique gearbox which looks like nothing special from the outside.

Inside however - he's got something pretty strange going on. The differential is a geared diff that he's been running for the past three years and ABSOLUTELY won't give away it's internal secrets to us mere mortals.

The differential has the usual 'differential' action so one wheel will turn more around a corner but most of the time it locks or has a limited slip action. If the car lifts a wheel when going round a corner for instance, the car wont lose momentum and the wheel with the most grip (the one on the ground) will have full drive. Interesting - wish we could get to see inside!



If any of you guys were there to see it... did it perform well or not??? Often hard to tell if these home-made solutions are good or not, as "mad scientists" like these seldom are the best drivers...

[Razer]

Originally Posted by SHY

Indeed! This was why Team Associated were so successful from the get go! They designed their RC cars as purely RC cars with new ideas, and not trying do downscale a 1:1 car Those who did try to downscale 1:1 car more than anything else ended up with way too complex solutions, and WAY WAY(!!!) too heavy cars!

We also need to remember the INSANELY big jumps our cars face! Only thing that slightly resembles an upscaled RC as I can think of right now are those Paris-Dakar buggies. They have very long suspension travel and can jump like a kangaroo



B-fast stuff???

But guys, have you all read about this?
http://www.oople.com/rc/photos/euros2010/day2/

Georg Kotzinger from Germany was running a pretty standard looking Associated B4.1 buggy - but we got a tip off about his unique gearbox which looks like nothing special from the outside.

Inside however - he's got something pretty strange going on. The differential is a geared diff that he's been running for the past three years and ABSOLUTELY won't give away it's internal secrets to us mere mortals.

The differential has the usual 'differential' action so one wheel will turn more around a corner but most of the time it locks or has a limited slip action. If the car lifts a wheel when going round a corner for instance, the car wont lose momentum and the wheel with the most grip (the one on the ground) will have full drive. Interesting - wish we could get to see inside!



If any of you guys were there to see it... did it perform well or not??? Often hard to tell if these home-made solutions are good or not, as "mad scientists" like these seldom are the best drivers...

It must be a miniature Eaton Detroit Truetrac then Used the big version in my Ovlov, absolutely brilliant! Doesn't look too advanced in terms of making a miniversion either...


Shy, don't you read anymore? B-fast is mentioned for balls and rings every time someone complains about their balldiffs;-)

[SHY]

Tell me more about that diff! Looks like a medieval torture instrument! Sure does look long lasting!!!

Only audio books these days! Link please kiddo!!!

Ovlov? Lada model???

Btw got a 22 yet? Tempted to get one myself...

Then there's this thing: Fiorini center diff ("torque reactive differential")

http://www.rctech.net/forum/electric...tial-mbx6.html



Would center diffs be worth having in a 1:10 car? Or why not vs. 1:8?