I'm looking at making a gearbox mount like the (very!) rough drawing below. Can anyone recommend some suitable rubber mounts?

Blue is the gear box, black is a 3mm plate and chassis brackets. Red are the rubber mounts.

I'm looking for rectangular mounts up to about 50 mm wide, 150 mm long (or 3 in a row at 50 x 50 mm). Height isn't massively critical, although I don't want them too wobbly. The mounts could be angled on top like in the lower drawing, and I think that would actually be better to stop sideways movement.


Description

I do have a square bobbin here with me for an exhaust which seems a nice size, if a little tall, but I'm not sure if a few exhaust mounts would be stiff enough?

is that for a type 9 rear mount?

If so I bought a HD ford one,. about £10 or something...

It's for a Mazda MX5 5-speed. It has some M14 holes at the bottom going front-back but they're level with the bottom of the chassis. Can't lift the gear box any higher and can't have a rubber mount under the gearbox. I did try turning a Type 9 mount 90* a while ago but it was too narrow to fit onto the Mazda gear box.

I should have clarified that the drawing was looking forward through the transmission tunnel.

ok, understood.

Have you tried trelleborg AV, or similar?

boing

hth

Have you got some pics of the gearbox in the chassis?
(I've googled for pics but can't see any that sound like your setup - most look like they have more space underneath)


My vote would be for the setup shown at the top of your sketch.

Your engine mounts should be taking care of any twisting loads etc - by making the gearbox mount that can take too much of this sort of load can actually create extra stress.

The basic principle to avoid over constraining it is to support it at 3 points (because tripods are naturally stable and self aligning) and avoid having 2 mounts trying to restrain the same direction of movement.

So if the 2 engine mounts acting together can restrain it in nearly all directions and rotations - they only need the gearbox mount to hold its weight up (and stop it pitching up and down) - any more than this and it can create stress as the different mounts fight each other....

[Edited on 3/3/2016 by mcerd1]

[Edited on 3/3/2016 by mcerd1]

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50 mm wide, 150 mm long

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We've been using polyurethane TVR suspension bushes from SuperPro here for engine and gearbox, and even diff mounts, since the late 80's.

They fit into 1 1/4" od x 10g tube.

Done a few MX gearbox rears, just as you require. 5 & 6 speeds are the same.

Cheers,
Nev.

I used these in my mk3 2.0 fiesta conversion. Coped with the power no problem. Albeit it was FWD. cheap to replace too.

https://www.ebay.co.uk/ulk/itm/121575605331

I did the same and used TVR gear box mount rubbers.

Land Rover Series 2, 2a & 3 Engine and Gearbox Mount NRC2052 277513

Locost and plenty strong enough for bouncing around a field.

They don't need to be 50 x 150, that's just how much space I have and I wasn't actually sure what size I could get away with.

Those Fiesta and Land Rover ones look like just what I'm after, thanks.

If I just have one mount on each side, I could bend some 50 x 5 mm bar to shape and bolt it to one of the holes on the gearbox. That seems like a simple way to do it. Poly bushes would need a bit more fabrication with brackets etc.

I did come across Markymark's Fury build with the RX8 gearbox. The box is a little different but the mounting point is the same. In mine, the bottom of the gearbox is level with the bottom of the chassis. I don't have any space to lift the box up at all, so I'm not sure what's different with his.

Again, that's a bit more fabrication than just a bar sitting on some rubber bobbins.


Gearbox mount

http://www.locostbuilders.co.uk/forum/4/viewthread.php?tid=160426



Edit:

Here's how I've got it mounted now. It was kind of a temporary thing to get the car moving around. My plan is basically the same but with rubber mounts on the chassis brackets and the metal plate/bar bent to sit on top.


Description

[Edited on 3/3/16 by Furyous]

Whilst I've got the earlier box, and it's mounted a little differently, this may give you some ideas for other options if you need them. My rubber exhaust bobbins sit inside the bit of cut open box section. This arrangement should work as well if the tubes that bolt to the chassis were angled down rather than up.

[url=https://flic.kr/p/oi8BBk]

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Originally posted by Furyous
Here's how I've got it mounted now. It was kind of a temporary thing to get the car moving around. My plan is basically the same but with rubber mounts on the chassis brackets and the metal plate/bar bent to sit on top.


Description

[Edited on 3/3/16 by Furyous]

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