Model: (Click to see more) 58211: Rover Mini Cooper Racing
Status: How To Guide
Date: 10-Nov-2013
Comments: 15
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Fiddling on my Monster Beetle Slipper clutch last year, left me thinking a lot about different Tamiya bearing sizes. Having used sealed gear diffs for a while on my TB03, 417, and my M05 and M06 chassis, I still do not understand, why Tamiya doesn´t bring out a sealed diff for the M03. This would be a great seller for FF01´s, Manta Rays...
Then my Race buddy Jochen donated me his old M03 beginning of the year, as he cleaned out his mancave. It was quite battered up, but as I had all M-chassis with exception of the M03, I decided to restore it as fun runner. As the ball diff was done, an idea came to my mind, which I call now the '1280' trick: It goes rather simple: Grind up the bearing housings in the chassis from 11mm to 12mm, to fit 1280 ball bearings! Then I used a Spec-R oil filled M05 gear diff, which uses 1510 bearings. The Spec-R seemed ideal to me, as it is symmetric and has quite tough plastics. This was needed, as I had to turn down the bearing seats from 10 to 8mm to fit into the 1280 bearing. Finally, I grinded the chassis holes for the diff shafts to 10,5 mm. This is needed, as the diff has to go in completely with bearings and outdrives mounted. Now the door is open for a quite reliable runner without fear off a slipping diff.
I´ll also try some diff setups with very thick oil on this one, as the Mini experts do on RC-Tech.
The tools I sourced really cheap on the 'Faszination Modellbau Friedrichshafen' last week. So it was less than 20 € for both. Worth every cent, it worked really good. Can´t wait to assemble the whole Mini and try it on the track!

1150/1250/1280 bearings are typical Tamiya The 12 mm drill i bought for 7 €... The second one I used for the last mm´s Material enough on the M03 bearing seats. Test fit, already getting there! Diff comparison Spec R / M05 std. Spec R uses 1510 bearings like M05 ball diff. Thank god my Dad has a lathe! The result is the '1280 trick'. It´s in. Can´t wait to try it!

Comments

Poul_F

10-Nov-2013

What a cool idea ! Gear diffs are much easier to maintain.

ruebiracer

10-Nov-2013

Thank you Poul,
I´m really happy that it worked so far, as I hoped.

Steffen

11-Nov-2013

Neat trick, good work!

Aurigarius

12-Sep-2017

Like that. Maybe I'll try that on my old 03 as well

ruebiracer

12-Sep-2017

Car is still going strong. My friend Jochen uses it in our Mini Championship, and won even A-finals with it. (and even left me behind in the race).
Only service were a refill with 20k oil after the diff set in. No damages on the gear so far.
Can only recommend this, if your tech regulations allow it. But for a fun runner, it ´s useful as well, very low maintanance needed.

BruiseWayn

13-Jan-2021

Wow you are an inspiration. I love the TA03. I have yet to get 1 back since i got back to the hobby, sort of.

Do you think hypothetically it would work with a TA03 and the older cars? I went through some of the old manuals; TA02, TA03 etc. i am not sure its possible to drill out the space needed to fit a 12mm bearing.

Instead, do you think a '1170 Special' will work? Also does it absolutely have to be a Spec R gear diff?

ruebiracer

13-Jan-2021

Thank you for your kind words! It should principaly work on TA03 and TA02 and derivates, too! Bearing seats would have to be checked, if there is enough material. But in the end its just 1 mm more in diameter, so 0,5 mm thickness loss on the bearing seats. Was no problem on the M03, my friend is stilll running it this way in hard Racing.
1170! Didn´t know that this ball bearings exist! I chose the Spec R diff, as it had plastic side outdrives, which where good to work on in the lathe, and had much material. Although the screws are accessible with the bearings on. Other manufacturers would have to checked for the modification. On the Spec R, I think that the further reduction to 7mm outdrive diameter could still leave enough material for not getting problems! Interesting input, thank you for that! This could really enable the use of these diffs in the TA02/03 much more easy. Because the gears are not split l/r on thes cars, it´s much more difficult to enlarge the bearing seats to12mm without special purpose tools...
Guess i have to think again about that mod! And let´s hope you still can get Spec R diffs thes days!

BruiseWayn

14-Jan-2021

Thats the problem. The availability. They can't be found anywhere. The diff case and cover for sale from THQ i think, nothing more.

It seemed that the 3Racing diff was the one the guys on the RCTECH M05 thread went for after their Spec Rs failed them, and were glowing about them. They are still available too, so i had a good look @ them but sadly, from pictures i don't see that the aluminum cover has enough material to take out whats required

There's the Yeah Racing one but that thing also has an aluminum cover. Again, not enough material on the seats.

Also you mirror my thoughts exactly on the whole gear diff thing; why doesn't Tamiya make one for the older cars. Bloody hell it will open a flood gate because it can be used on almost everything back to the bloody Manta Ray....

ruebiracer

15-Jan-2021

Yes, you´re totally right! Even the old buggies could get a gear diff then. But you really got my thoughts going again on this theme. As you also found out, 3Racing gear diff and Yeah Racing are not suited for this mod. I´m not so sure about the Top Racing gear diff, but that´s also not so easy to get nowadays... Do you know, if you can get 1150 ball bearings somewhere, with 3mm width instead of 4? And shielded at least on one side? I know 1050 is available from the double cardan shafts in 3mm width...

BruiseWayn

15-Jan-2021

as i remember, the Top Racing one was the first one to go out of stock when the Spec R was still available. I been thinking abt a gear diff for the older cars for years. Even though i left the hobby but i always kindda kept up with news and what not.

I contacted 3Racing prolly a year or 2 ago asking them if they had any plans to release something like that but they shot me out of the sky lol. This morning i asked Yeah thru facebook if they felt it can be done. But they confirmed my 80% certain thoughts that it cannot be. Was hoping for a diff opinion ahah.

The case and cover for the Spec R diff are still available.... the question is, where am i gg to find the outdrives and the gears and what not. Also the reliability is questionably but as you say, your friend is still thrashing it with no problems so... haha

As for the bearing question.... try

[Click here]

Because seriously... whats not made in China these days. But please, contact them first. i see some listings with seal bearing pictures but may not be accurate.

ruebiracer

15-Jan-2021

I feel it can be done, imagine the spec R diff I used with Aluminum cover / housing on the outdrives. So your mentioned 1170 bearings could be used for sure. I even feel it would be stable enough on the Spec R housing turned down to 7mm.
Spec R brought later on a HD version of this, but it is even harder to find nowadays. And I don´t remember exactly, if only the internals were different, or the housing, too. Thanks for the link! There are really 1150 ones in 3mm width available, but shipping costs at the moment are crazy even for such small part. I still think such a 'Retro' diff would be a big seller for hazzle free Retro Racing, imagine it on a FF01 with 300k oil, or in a Topforce Evo with Brushless to stop the ball diffs from slipping, haha! It would fit so many TAmiya models including M01/M02 and all the others. I have the strong feeling it can be done in the end, just no company has the motivation at the moment. I feel I have to dig in again for a solution!

BruiseWayn

16-Jan-2021

i think the people behind Spec R has a new website. trying to get in touch wif them.

if i can't. then probably get the SR case halves and buy 1 3racing diff and c if i can mix/match parts to fit. keep u posted?

ruebiracer

16-Jan-2021

For sure, keep me posted! I always wondered what happened to Spec R, as they made quality stuff. In fact they made the first TB03 gear diffs, long before Tamiya brought them in TB04. I have some still going strong and being lighter than the Tamiya ones...

rc-martin

26-Aug-2021

Great mod, I've just fitted a Spec R diff that I had for my old xray into the standard M03 diff final drive. Machined the Spec R down to slide into the M03 gear which I removed the inners from. Turned the outdrive bearing mounts to 7mm and used 1170 bearings

ruebiracer

26-Aug-2021

Great info Martin! Didn´t know about the 1170 size! That´s definetely an step easier and still leaving enoug 'flesh' at the diff outdrives. And clever to change the Xray gearing into M-chassis size! Congratulations!


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