The Lotus Grand Tourers

Out of interest Pete, why the new block?

Shaun

shaunw wrote:Out of interest Pete, why the new block?

Shaun

The 907 had a few problems with main bearing wear due to flexibility in the casting design of the block/girdle. The 912 block/girdle is much more stable; the castings are stronger. I was going to build up the 907 engine with a view to building a stronger engine later, but I've decided not to waste time by building two engines! . Of course this will let me build a more powerful engine without running into problems! .

Pete

Pete Boole wrote:

shaunw wrote:Out of interest Pete, why the new block?

Shaun

The 907 had a few problems with main bearing wear due to flexibility in the casting design of the block/girdle. The 912 block/girdle is much more stable; the castings are stronger. I was going to build up the 907 engine with a view to building a stronger engine later, but I've decided not to waste time by building two engines! . Of course this will let me build a more powerful engine without running into problems! .

Pete

Nurse! He's at it again.

Just one more - please!! I promise I'll be good!!

Pete

So here's the bit that's been holding me up for weeks:




Yes, it's a tapered roller bearing outer race from the diff crown wheel carrier and it does this to the differential casing:






Because the bearing has a large radius on its outer edge it reduces the diameter of the contact patch to less than 4mm and as a consequence it buries itself into the casting, leaving the groove you see in the photo. This immediately removes all the pre-load on the bearings and the diff becomes useless. I've now got four diff casings and they are all the same; some worse than others, but all unusable without machining the surface flat again, and it's difficult to get in there, so I've spent the last few weeks working out how to machine the bearing surfaces flat again. I've built a special one-off tool that allows me to re-face the casting:





To help reduce this problem in the future (especially because the diff might be subject to a little more torque ) I'm having some bearings made with reduced radii on their outer edges that will increase the bearing face area by over 90%. Of course if Salisbury had designed it better in the first place!!

Name-drop alert!!....

The company making the bearings for me make bearings for the Ferrari and Red Bull Racing F1 teams! .

When I get the bearings I can then re-build the diff (at the NEC) and get on with the restoration .

Pete

Always an excuse.....

... but a very good one.......

Progress coming soon! Hopefully

Pete

The sun came out today, and being inspired by the weekend's activities:





I decided to whip the body off!

Chassis in exceptional condition (although I won't be using it!). It was refurbished (not modified) by Spyder Engineering in the mid-eighties and has no rot on it that I can see - just a bit of surface rust here and there.

Pete

You selling the chassis Pete?

Hawaiis0 wrote:You selling the chassis Pete?

I am. Visitor to the show left his contact details - not too sure how serious he was.

Pete

Am i allowed to let it be known?

Yep - the sooner it's gone the better, now it's outdoors. Know someone who might be interested?

Pete

I heard a chap has rot on his and may be breaking the car otherwise. Trying to stave off the death nell. Let me know the price in case he comes back.

Little update; been doing a bit since the restoration show. Blast cleaned and etch primed - ready for top coat:




More problems caused by inadequately located bearings - front upright:




Thought this was scrap, but decided to machine it: The horrible brown tape is holding a balancing weight on!




bit better:




The felt seal will have about 0.5mm more crush than before, and the brake disc will be 0.5mm further inboard, but don't foresee any problems, and saved myself ~ £200 (both sides need machining) .
Still needs a new stub axle though.

I've found someone selling spacer kits that allow proper shimming of the bearings - this will prevent the inner races wrecking the upright/stub axle in future - proper engineering .

Pete