Gearbox Fitting - Chassis Changes

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Had to take a few steps backwards over the last few days to enable me to make enough room to fit some seats and an engine...

After visiting a fellow Locost V8 builder from a nearby town (Hi Bruce) I decided to rebuild my transmission tunnel to maximise seat room. Bruce managed to keep the tunnel width to a minimum and is still having trouble fitting his seats. My tunnel was 3 inches wider so I'd have ended up with a child's booster cushion for a seat! I also took some advice from Bruce regarding engine space and moved my engine and gearbox 3 inches further back to avoid my crankshaft pulley from impacting my steering rack.

Anyway, the tunnel has now been replaced and is almost complete with just a couple of extra uprights and some fillets to put in place. As you will see from the following pictures, I have also cut out tubes Q and C to allow the gearbox to go back into place. I have also changed the way that the two foremost 'H' tubes attach to Q and C by inclining them. This give more foot room for the driver which was another concern I had previously. Finally, I don't have a photo of it in place but I have modified the standard SD1 gearbox mounting and welded it to a couple of SHS tubes which will span across the tubes 'm' and 'l'

 

View of gearbox in place in modified tunnel

Rear part of tunnel. Just needs another pair of uprights and some cross braces

Here you can see how far back the gearbox is now. The mating face is just 93mm from the front edge of the bulkhead. I also fitted the engine block to establish a level and it looks like I'll have to make do with the sump being 2 inches below chassis rather than the recommended 1 inch. At this level the flat top of the rocker cover is 6.5 inches above the chassis tubes J1/J2 with the SU carbs sticking a good bit further up than that. Ideally I hope to get a Holley or Webber carb setup to avoid having a bonnet bulge the size of Mt. Everest!

Low angle showing transmission tunnel detail. Note how frontmost 'H' upright is sloping towards the gearbox at the top. It has to stay wide at the bottom to clear the clutch slave cylinder bulge. Also note staggered lower tunnel tubes. This is not ideal for strength but I will add in a fillet using 20mm SHS to restore strength. This arrangement was required to allow the standard gearbox mounting to be used and to accommodate the odd shape of the LT77 gearbox whilst maintaining a parallel tunnel width.

Next main development should be engine mountings followed by completion of the rear suspension. I can then turn attention to the front suspension and work towards getting this thing rolling!

 

Starting To Take Shape

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Quite a bit of progress from last update, both visibly and "non-visibly". When I say "non-visibly" I mean that some key decisions have been made or key parts have been sourced which may not be visible but are equally important.

The main non-visible progress made was in the resolution of the rear suspension dilemma. This has been my main source of delays in the past few weeks and it is a real step forward to put that behind me. The resolution came in the form of an MK Engineering de-dion suspension kit which I bought second-hand but unused from one of the other LocostBuilders.co.uk forum members (Thanks Chaz!) He bought it a while back but it is now surplus to requirements. He also supplied me with Sierra rear hubs, disks, hub carriers, driveshafts and a differential with mounting brackets. This comprises most of the rear suspension system with only trailing links, panhard rod and brake calipers left to be sourced.

The only problem with the above setup is that it is designed for a standard width chassis and I am using a +4" chassis. This has meant that I have had to effectively re-engineer the rear chassis to make it standard width in some ways and +4" in other ways to allow the suspension to mount correctly. In practice this meant moving tubes K3 and K4 outboard 1" each so they are now in line with A1 and A2 and also moving tubes RU1 and RU2 inboard 2 inches on each side to allow the de-dion assembly to articulate correctly without fouling. This also means that I have to mount my rear trailing links on the inside face of tubes M1 and M2 instead of the outer face. I intend to use spherical bearings to help minimise the intrusion into the cockpit and create a box section around the arms which should be okay. Since my chassis is 4" wider than standard the 1.5" intrusion on each side should not be a problem.

Recent Progress

As you can see, the rear suspension tubes are now in place behind the seating area. Note also that I've created the first section of transmission tunnel. I can't complete this until the diff position is finalised though.

Here is the diff and one of the shafts in place (roughly).

This image shows the changes made to accommodate the de-dion axle and ears. The changes are designed to allow the ears freedom to come down below the plane of RU1 and RU2 which is necessary on full rebound. You can see that I have highlighted the tubes involved and shown how they have moved. Note that there is now a clear line between the mounting lugs on the "ears" and M1 for the trailing links.

 

Well that's about it for now. I'm busy creating a CAD drawing of my chassis in Solidworks so that I can see how things will go together before I actually weld them from now on...