Differentials = Balls (are gear diff gone forever?)
 

Re-staring RC, and gearing up, I met only cars with ball differentials...

What I don't like about them, is the requirement for maintenance

My first question(race) is : The advantage over gear differentials is only the ability to reduce freedom (by tightening). We could envisage the same with gears after all : very high viscosity grease(coarse adjustement) and slight tightening(fine adjustemen). Do you agree with that ?

Second question(play): for bashing around with insane motor power, ball differentials become the real weakness. Can some cars be fitted with gear differentials(I mean not toys, real cars like B44/B4, BJ4, zx5/RB5, D4, ...) ?

Thanks!

AE are coming out with the new SC10 and it comes with an gear diff.
So you can run an gear diff in a T4/B4.

Firstly I get about 4-6 months out of my diffs before they need attention, stock Kyosho parts but with Kyosho Ceramic main diff balls.

On top of that the ability to make an adjustment without having to strip the car down makes the ball diff a huge tuning aid. Also they are MUCH lighter which improves throttle response etc.

As for bashing you can just tighten them up a bit and set the slipper a bit tighter then back them off when you go racing and handling becomes the main focus again.

SC10 gear diff is the same weight as the Ball diff.........

Is it a direct fit into a B4 gearbox Pidge?

nope, you will need to order the SC10 gear box housing and rear plate, i think thats the only other parts you will need....

That's really good news, at least a solution exist

Pidge, I am impressed you have precise info like that : I could not find any details about sc10 parts on the AE website

Is that solution also valid for b44/bj4 ?

I use a 4.5 turn in a TC with 2 diffs no problem.
If you want geared diffs with electric offroad then how about 1/8th electric class. :thumbsup:

Remember with smaller wheels there's much less stress on the diff... ;)

Diffs in a touring car have an easy time of things.
Small wheels and no bumps or jumps mean they have to deal with far less torque, and much lower shock loadings.

Was wondering if kyosho do a geared diff that fit's the ZX5 gearbox, myself. - Maybe something from one of their nitro cars.

I'm also reckon that a bit of mass in the transmission could be quite useful.

I'm sure that was one of the main reasons losi Hydradrives made the car so smooth to drive.

Good point... Actually the ZX5 being also a RTR/cheap platform, I would expect some gear diiff in the RTR ?

ZX5 RTR uses the same basic diff design as the rest of the ZX5 series

Losi xxx-cr can also use gear diff. One guy up here in the north has modified his and it works fine.

Looks like I am not the only person to want geared-diff...

After Asso latest car, the SC10. It's now Durango that uses gear diff. Could it be that the cat sx was the last car to use ball-diff ?:D

That is bad news for the RC manufacturer though? (was a good cash caw these balls put under extreme stress between plates)

So has anyone put an SC10 gear box in a B4 yet? Is it a worth while mod?

Er... not quite! Stress on the diff is a function of the torque the diff has to transmit, and the weight of the car, not the size of the wheels. In off-road, there is so little grip compared to TC that the diffs take less of bashing.

As Warped says, the main stress that an Off Road diff takes is the constant shock loads of the car skipping across the terrain, and the wheels spinning up and then gripping again. What amazes me is the abuse an off-road diff will take before it cries "enough!" In a TC, it is the large amounts of torque in quite a weighty car that shorten their life, and in off-road that isn't the case. Wheel diameter is just a reflection of gearing, not load.

Either way, a geared diff is going to be much stronger from a life point of view, but will need more work to tune. However, once oyu have the space for a geared diff, you have the space for a Torsen diff - and they are awesome!

Sorry but i have never seen a TC wheelie, where as i know numerous 4wd's that you can flip on grass. I remember from TC that they would spin the wheels up on the line, this is not the case with off road unless its wet or on dirt

typical 'UK' off-road - dry astro turf with yellow mini-spikes is incredibly 'bitey'

xxx-s plastic outdrives can be had for lunch in the xxx-4

so could the xxx-s front spool in a xxx-4

and blowing xxx-s one-ways in the front of a xxx-4 was considered normal.

all of these items lasted (at least for 5 minutes) in the xxx-s

:D Voice of experience there Chris

With larger diameter wheels the diff is spinning slower for the same ground speed. As power is 'torque x RPM', given the diff is spinning more slowly to give equal power transfered the torque must be higher :)

So what effect will a gear diff have on a 2wd and 4wd?

I had a gear diff in my Serpent S400 TC, was good as far as maintence was concerned but it used to kick the rear end out under hard acceleration due to no slip.

having read through the thread, does anyone have a definitive list of the parts needed to convert to a gear diff on a B4 ?.

i reckon you'd need the following :-

gearbox halves
rear chassis 'T' piece
outer diff bearings
rear motor guard ?

anything i've missed ?.

does anyone know when they might be available ?

http://67.199.85.166/main/productdet...ory=3015.sc10x

http://67.199.85.166/main/productdet...ory=3015.sc10x

al least

nick,

As far as im aware you need:

Gearbox Halves
Rear T plate
Gear Diff Kit
Bearings.

Dont think you need the motor guard.

thanks for the info. i forgot the diff itself off the original list - doh !!

i'll keep a look out for the spares when they arrive in the UK

i realise that its a bit early to speculate but any thoughts on a good starting point from an oil weight point of view ?

cheers,

nick

Cool! I will have a look on the AE website for the part numbers, not sure if will be a waste of money for use on the B4? But will be interesting to see the results.

I wonder if anyone across the pond has tried it yet as they prob have all the parts in stock to do it.

I know that it's very easy to convert XXX to gear diff - I belive theat you need only Speed-T gearbox and gear diff? Rest looks the same.

Just got the SC10 manual down loaded, looks like you will need:

9826 gearbox case
9832 10x16 bearings
9827 gear diff kit
9818 rear t piece

Time to get them on order!!

Sorry it's desert truck that has gear diff.

:thumbsup: Durango are coming !!! with gear diffs:woot:

what is a Torsen diff?

that is a limited slip diff,

if your going to change over to the geared diff, you may as well take full advantage of it and get a set of diff oils, so that you can get the right amount of drive you need,may be a spare diff for quick oil changes.?

Torsen diffs are TORque SENsing differentials.

They basically work via a group of interlocking worm gears. The helical tooth form on the worm gears create load between each other the more torque that is put through them, which in turn causes more resistance between said gears.

The net result of this is that the wheel with the most torque capacity (thus most likely to have the most grip) will load the diff up in it's favour. The more load the more torque is sent to that loaded wheel.:thumbsup:

Equally, unlike a limited slip differential, if there is no load across the diff there is no torque bias thus you can still spin up an unloaded wheel.

The advantages over both open & limited slip diffs

1) It doesn't ever fully lock so it is unlikely to ever try and drag the car left & right as it accelerates over bumpy surfaces as each wheel becomes loaded/unloaded

2) It doesn't ever fully lock so it means that on a steered axle there is always a true differential action so both inner and outer wheels correctly are driven and thus the steering loads remain stable as you come on and off the power

3) The torque biasing is much more gental thus it looks after the transmission better as there is less violent load changes.

Disadvantages to LSD

1) It never fully locks so on dead smooth surfaces with very consistent grip levels it will always divert a little of the torque to the wheel with little load (or indeed unload the diff altogether if traction is full lost on one wheel)

Disadvantages to open diffs

1) weight, it's always going to be heavier than a simple bevel gear open diff
2) cost


When to use what type of diff?

Open diffs are cheap and perfectly adequate under most light load situations. Also great for very smooth easy to drive front wheel drive cars.

LSDs are great for smooth tarmac use and / or when your main concern is that you always have to get 100% of the torque to a tire contact patch (which may or may not be able to use it). Great for the rear axle of off-road / low grip cars too as the locking can help you turn the car on the throttle.

Torsen diffs are brilliant for variable grip surfaces or over stressed axles and the daddy for the front of a powerful front wheel drive car or front axle of a 4wd car.


Basically anybody who has driven a fast road going front wheel drive car with a traditional LSD will tell you that on smooth surfaces it's fine but when the roads get rough or the grip level gets patchy it is constantly tugging at the steering and the car becomes a real handful.

When I first build my first turbocharged Mini I ran an open diff. Basically I was constantly loosing tractive effort due to spinning a wheel up and the constant change in load beat the diff / drivetrain up so badly it lasted less than 1000 miles!
Next I fitted a traditional LSD (on the lowest available ramp setting) and no word of a lie it was so aggressive it would rip the steering wheel straight out on my hands (thought I'd broken a thumb once) and it would need a 2 lane road to be able accelerate as when the diff locked it threw the car violently to the right!
As soon as the Quaiff Torsen diff went in the car was no more difficult to drive than it had been with the 998cc lump in and hardly ever broke traction on straight line acceleration.

Hope that helps to explain

Different types of Torque / Torsen Diffs .

http://www.thercshack.com/ProductImages/mp7a.jpg http://www.ofna.com/teamjammin/image...-10596-big.jpg

http://www.losi.com/ProdInfo/Gallery/LOSA3600-Gal1.jpg

Last picture looks like a locking diff to me, ramp type LSD??? Hard to tell for sure from such a small picture (I need to get work to buy me a bigger monitor)

top one is torsen diff, LSD diff don't lock up fully ether, hence the name limited slip diff

just fitted an SC10 diff in my B4 using the parts listed previously. it all went in very well indeed :D (thanks to Marc from MK Racing)

using 1000wt associated diff oil it felt a bit tight to start off with but after a quick 5 min blast around the garden, everything has freed up nicely. it feels like a tight(ish) ball diff at the moment but will free up a bit more after racing tomorrow i would think.

i'm happy so far but we'll see what it goes like on the track....

Nope I prefered gear diffs on carpet too, and funnily at Worksop. I prefered vaseline packed in and that helped big time, but you may prefer thicker.

how did it go?

I'm still waiting for the diff to turn up, got all the other bits sat here! Hope Cml get them instock soon!