Replacement F1 Diff Assembly

[sparkyboy22]

I have a HPI Super F1 that I am looking to take out for a few races.

The rear wheels are warped but it uses the wgt type fixings and I really should go with the same as the others are running.

Does anyone know if the rear axle and diff etc from a f103, f104 or f109 will drop straight onto a super f1?

Long shot I know!

[terry.sc]

The simple option is to just use WorldGT parts, after all they use exactly the same rear end as the Super F1. If you are planning on racing it then you will need to modify it to make it fit standard F1 wheels, the problem is almost every F1 kit uses metric 6mm diameter rear axle so they won't drop in without a little work. The exception is the HPI F10 which also uses a 1/4" axle like the Super F1, the problem is the HPI ball diff set has a list price of £65.

You can fit a much cheaper Tamiya or Tamiya compatible rear axle in there by opening the holes in the rear height adjusters to 10mm and using a pair of 6x10mm flanged bearings. Standard F1 axles would then drop straight in. You can fit F1 wheels on the front using Tamiya front steering arms.

The wider F103 tyres which you would want to balance out the front width are around 55mm in diameter, so should be just about big enough. The narrower F104 tyres are 60mm in diameter, but they will make the rear end about 20mm narrower.

[sparkyboy22]

I didnt realise the axles were different sized!

I was worried about the left/right offset! The distance from spur to wheel hub on each side.
Do you know if this is the same between the cars?

[terry.sc]

Having measured mine the HPI rear pod is 3mm wider than the F103 pod, but the HPI pod is offset 2.5mm further. A standard F1 diff will be centred if you use a 10mm spacer on the non diff side, but to end up at the same width as a Tamiya car you need to add a 2mm thick spacer on the diff side and use a 12mm spacer on the non diff end of the axle to get the alignment right.

Gearing isn't much of a problem as both Tamiya and 3Racing make a spur gear adapter to fit standard spur gears in the F1 diff, but the amount of movement in the HPI motor mount means it can cover the normal F1 gear range anyway.

[sparkyboy22]

I have gone for the simple solution and bought a F109!

[sparkyboy22]

Terry, I am having a look at dropping the F109 rear axle into the HPI Super F1.

My measuring skills are pretty poor, I dont suppose you have an F109 to measure against and let me know the size spacers required?

[sparkyboy22]

Also just realised I am a donut as the axle is metric and the ride adjusters are imperial.
The F109 rear ride height adjusters dont fit.

Has anyone come across metric versions? I think they are the same as the ones used in the RC10 and Cyclone 12?

[terry.sc]

The F109 is basically a set of hop up parts for the F103 that have had a chassis made to join them all together. The rear axle spacing is the same as I stated above.

As for the rear ride height adjusters, as I said earlier you need to open out the holes in the HPI adapters to get the F109 bearings to fit in them. The holes in the HPI adapters are made for 3/8" bearings, which are 9.5mm so you can enlarge them with a 10mm drill, then use a pair of 6 x 10mm flanged bearings to fit the axle into the HPI.