Tarmac Rally Stratos Build begins

[ByrneEngineering]

here's a good shot of the gearbox sterngthing plate, we milled it out of a 12mm plate so we could leave a 6mm edge to aid with welding and leave a 12mm rib, but that was overkill and due to a crippling Milling machine addiction, a simple 6mm plate would have been fine



Some more pics of the front strut mount to follow
cheers

[Basher]

Colin, Enjoyed a brilliant compilation of videos, the car looks and sounds great , good luck on the rallies , Cheers

[Stableblock]

Thanks Colin, Its been great to follow your rebuild and see everything you have done. I imagine I'm not alone with my workshop (and skills) envy! Good luck with your season.

Best wishes

Peter

[Strat Fan]

here's a good shot of the gearbox sterngthing plate, we milled it out of a 12mm plate so we could leave a 6mm edge to aid with welding and leave a 12mm rib, but that was overkill and due to a crippling Milling machine addiction, a simple 6mm plate would have been fine


cheers

I haven't actually seen an Alfa box fail in the bearing area but I have seen a couple that have worn through from rubbing on the inner wings when the top engine steady in the donor car fails.

The one I have seen that failed in a Stratos replica (former member on here) was much more catastrophic and the weak point was actually around the outer edge of the end casing.
The increased traction of the mid engined layout must have been too much and the thrust put back up the shaft from the crown wheel was too great for the casing.
The old 164 gearboxes were much stronger in this area where they had the additional bolt on end casing.

[Guy Mayers]

Isn't there a similar problem with Integrale boxes on uprated cars? I have a vague memory of casings being machined around bearing houses to accept a sandwiched steel plate to strengthen them.

[Strat Fan]

Isn't there a similar problem with Integrale boxes on uprated cars? I have a vague memory of casings being machined around bearing houses to accept a sandwiched steel plate to strengthen them.

I can't comment on the Integrale but there is the 3mm steel strengthening plate which can be added to Fiat/Alfa boxes between the bell housing and the gearbox casing which is used to help prevent the diff/crown wheel from separating from the pinion shaft. This requires 3mm to be machined from the gearbox casing to me it fit.
Neil did this to his old 164 box. That bit didn't fail but he stripped 4th gear shortly after....

[westonTB]

Thanks Colin, I have learnt a lot from watching all your video's and the 105 Alfa stuff, 2 years & on the track = Result! Me = 6 years in and still bleeding air out me brakes!!! = idiot.

More Beer needed to help I think.

[Bernard]

If I remember correctly when he machined Erics gearbox for me he took 1.5 off the bell housing and 1.5 off the Gearbox casing.

I can't comment on the Integrale but there is the 3mm steel strengthening plate which can be added to Fiat/Alfa boxes between the bell housing and the gearbox casing which is used to help prevent the diff/crown wheel from separating from the pinion shaft. This requires 3mm to be machined from the gearbox casing to me it fit.
Neil did this to his old 164 box. That bit didn't fail but he stripped 4th gear shortly after....

[Strat Fan]

If I remember correctly when he machined Erics gearbox for me he took 1.5 off the bell housing and 1.5 off the Gearbox casing.

It sounds viable, I've never had one done.

[ByrneEngineering]

The one I have seen that failed in a Stratos replica (former member on here) was much more catastrophic and the weak point was actually around the outer edge of the end casing.
The increased traction of the mid engined layout must have been too much and the thrust put back up the shaft from the crown wheel was too great for the casing.

So this was the sort of failure we were attempting to avoid with the additional strap


Now 'm not saying this is absolutely correct, but here was our thinking on the situation


- the failed section is after the gearbox mount, so it won't be subject to any loads generated between the diff output to the chassis


- the only Force that part of the gearbox casting is subject to is created from the gear shaft bearings


- As the gears are loaded up the shafts will try and spread apart, this is reacted by the bearing housings in the casting


So our thoughts were, a failure occurred in the casting between the 2 bearings, as mentioned it is very very thin in there, once a crack formed the 2 gears spread apart further and caused the carnage seen in that photo


What would be super helpful would be a photo of the failed casting parts, if the 2 bearing housing are still attached together in the end plate that would falsify our theory