Ball differential for Hornet/Lunchbox chassis

[kontemax 1725]

Hi people,

I would like your opinion about it.

I could, through a company that I know, design and build the ball differential for this frame.

Obviously would fit on the following models:

Hornet

Super Hornet

Grasshopper

Grasshopper 2

Vanessa Lunchbox

Montero

Pajero 58044

Midnight Pumpkin

and all chassis derivatives.

I'm not sure about the DT01 Madbull and similaria, Falcon or other, but maybe you can help me about this.

Do you think the product would sell?

Or it would remain in my house?

And what would be the right price?

Many thanks

Max

[SteveU30 1011]

Well I would have one for my Lunchbox that's for sure!! I think it would sell really well as most of those models are still really popular and I think a ball diff coupled with a nice brushless setup would work really well together.

Not sure on price, I think it would have to be reasonable to sell in any great quantity though!

[mr crispy 2293]

What is the advantage of fitting a ball diff over the standard gear diff on such a basic chassis?

Now if you could make a diff locker that just drops straight in, I'd be interested.

[Butler 338]

A locked diff on a lunchie? It'd never turn!

[GregM 1109]

I would like your opinion about it.

I could, through a company that I know, design and build the ball differential for this frame.

This sounds interesting, although I've got to admit I am used only to geared diffs and have no experiences with ball diffs so far. I would like to know the advantages and disadvantages of a ball diff for this purpose.

I'm not sure about the DT01 Madbull and similaria, Falcon or other, but maybe you can help me about this.

The DT-01 chassis uses an encapsulated gear differential in traditional Tamiya style, unlike the old "open" geared diff of the Grasshopper, Grasshopper II and Lunchbox chassis types. If you browse through the manuals (most of them are available for free download at www.tamiyausa.com ), you'll see the differences.

[mr crispy 2293]

A locked diff on a lunchie? It'd never turn!

It'd be a better beach runner though and wouldnt dig itself into a hole and spin up one whee on sandl

So far I've locked the rear diffs on 2 CC01's, a TL01 and a TA02 and I can't say I've noticed a massive reduction in their turning circles. Now the LB isn't great when it comes to corners so you maybe right, but if that's the case I can swap the old diff back in.

[kontemax 1725]

A ball diff is a limited slip diff so it's in the middle between a totally free gear diff and a locked diff.

A ball diff makes the vehicle more driveable and in case of a lifted rear wheel from the ground the car will not stop with a spinning wheel.

DT01 and Lunchbox have different gearboxes for sure and different diffs but I don't know if they fit and it's impossible to check it via manual.

Max

[BadWagon 146]

I'd be interested Max, depending on the cost of course.

[shenlonco 1156]

I would say use a sealed oil filled diff so you can use oil to tune it... How would you reach a ball diff in the hornet type rear to always adjust it? Oil diff all the way that would be awesome!!!

[kontemax 1725]

Oil diff it too much difficult to do I think.

Don't know, there will be problems with leaks.

Max

[waterbok 1282]

price of tamiya diff's go from 25€ (DT02) to 37€ (SRB), so if you want to sell, then somewhere in that range.

that reminds me that I wanted to drop some AW grease in my WW2 geardiff.

[OldSchoolRunner 116]

Lets see some pics? If these people have done this before I am sure they have pics Max?

OSR

[qatmix 794]

I can't really see what it would give you over the std gear diff in something as primitive as a grasshopper. The rear end isn't planted so you will have a lot of digging out that will quickly lead to it needing to be serviced. The gear diff is tough (I have a hornet that's 20 years old and has been to badword and back a land the fit has never broken). If you want a stiffer diff pop some AW grease on it.

Don't get me wrong, I live this hobby and I like the idea, but I can't see any benefit from it other than it would be different to stock.

There is a saying, you can roll a turd in glitter, but its still a turd .

[qatmix 794]

Btw I mean diffing, not digging but you can't edit posts on a mobile!!!

[slinky2000 0]

I'd be interested that's for sure!

[XV Pilot 1936]

I'm not sure about a gear diff due to the need for adjustment and maintenance, and I get where you are coming from about the issue of leaks on an oil-filled gear diff, so how about a third option?

We all know that we can limit the slip of standard gear diffs by filling them with sticky grease, but this isn't really an option on the Hornet/Grasshopper/Lunchbox/Pumpkin diff because it is open to the rest of the gearbox. Smear it full of sticky grease, and the grease will quickly distribute itself all over the inside of the gearbox, making everything sticky and not doing it's job on the diff.

So how about making a pair of covers for each side of the standard gear diff that will keep the grease in? They don't need to make a perfect seal like they would have to on an oil-filled diff, and such an arrangement would need a lot less maintenance than a ball diff.

What do y'all think?

[MadInventor 3884]

I'm not sure about a gear diff due to the need for adjustment and maintenance, and I get where you are coming from about the issue of leaks on an oil-filled gear diff, so how about a third option?

We all know that we can limit the slip of standard gear diffs by filling them with sticky grease, but this isn't really an option on the Hornet/Grasshopper/Lunchbox/Pumpkin diff because it is open to the rest of the gearbox. Smear it full of sticky grease, and the grease will quickly distribute itself all over the inside of the gearbox, making everything sticky and not doing it's job on the diff.

So how about making a pair of covers for each side of the standard gear diff that will keep the grease in? They don't need to make a perfect seal like they would have to on an oil-filled diff, and such an arrangement would need a lot less maintenance than a ball diff.

What do y'all think?

This sounds like the most common sense option, although I think the spur gear runs pretty close to one side of the diff so may not be feasible in practice.

My ideal solution for the hornet / grasshopper would be to ditch the standard gearbox and fit something where you have a gearcase with the suspension directly attached with relatively short shocks, such as a thundershot rear gearbox. This gets rid of all the unsprung weight of the gearbox and motor, and gives independent rear suspension into the bargain. The thundershot rear end also has an enclosed diff so sticky grease is an option, and it's quite high geared when hotshot sized wheels and tyres are fitted.

[GregM 1109]

The DT-01 gearbox uses an enclosed differential. It can be easily attached to the Grasshopper II chassis tub, as Tamiya did it with the Rising Fighter. I'm not sure if this gearbox could be attached to the Grasshopper I chassis, too.

Using the DT-01 gearbox however will restrict the pinion choices to 17T & 19T, in contrast to the Grasshopper gearbox (18T, and 10T when using the Lunchbox motor mount). The smallest pinion you could fit to the DT-01 is 15T, when using a custom motor mount. Another disadvantage of the DT-01 gearbox are wheel axles which uses splines for unique metal hex wheel adaptors instead of regular pins. The hex adaptors strip frequently if the wheel locknuts aren't 100% tightened down and using large Mad Bull wheels. So extra care and pristine locknuts are needed to prevent damage.