Gearbox mount

[morris]

Hi all,

Has anyone actually mounted a gearbox yet using the new style mount or am I the first to try? I've asked Marlin if they have any photos but looking through other recent builders logs I think I'm the first.



The first problem is that the rubber doughnut fouls the back of the gearbox preventing you actually bolting the V shaped bracket on. this is easily solved by sticking a smaller doughnut in. The real issue is how to mount it up underneath the transmission tunnel without fabricating extra brackets to bolt into the sides, just like the old on. If this is the case it's actually a weaker design as it's no longer a single piece of steel. The only place you can fix it vertically is through the lip that the floors sit in which is only 25mm deep. With a pair of M8 bolts either side it would certainly take the weight of the box but I'd not have much confidence in it once loaded during driving. Maybe I'm underestimating the strength of that lip?

[peterux]

From memory, when the engine and gearbox are bolted together they are quite well balanced when installed on the engine mounts so there is actually very little weight at this point.
Let's see what Mark says, but I suspect the flat piece is mounted with two M8's each side and will be strong enough.
I hope those tunnel lips are strong because they take the passenger and driver seat runners
And thinking about it, that flat piece will add to the strength of the tunnel by not allowing any tendency to 'spread' under sideways the stress from the seat runners.

[mashtun]

It wouldn't surprise me if it attaches like you suggest - the one for the Cabrio does (well did in my kit, which was one of the first - I don't know if the design changed later). And mine didn't use anything as beefy as M8 bolts - just 3 x M6 machine screws each side (as used to fix the rest of the floor in place).

I think you'll find it's quite a stiff arrangement overall, particularly when the floors are in.

[morris]

the thing with the floor and seat is that the load is spread right round the lip rather than in a single point. I was planning on running some box section under the seat mount points the full width of the chassis because the floors provided strike me as too flimsy, I'd be getting into the car very gingerly

It was more the stress from the weight of the box under cornering that I was worried about because as Peter says, most of the downward weight is taken at the front by the engine mounts. It sounds like it should be ok though

I'll see what Mark comes back with

[morris]

Marlin have confirmed that the mount does need to be bolted up through the lip but have also pointed out that if I do it though the floor panel too, that will further strengthen it, something I hadn't thought of.

I'm now back to the doughnut problem.

I thought that one of the smaller 58mm ones from CBS would do the job but after measuring up I need to loose 20mm from the front side which equates to swapping my 80mm diameter on for a 40mm diameter. That will mean way too much overall lose of stability so my current plan, unless Mark comes back and tells me of a more suitable part, is to hacksaw 20mm off the front of the doughnut. that way it will retain much more of the lateral and longitudinal stability of the 80mm than the overall lose in all directions of a 40mm doughnut.


some pics of the issue

[morris]

TaDa, this should solve the problem. To be honest the over hang on the mount probably wasn't providing any support anyway