Gearbox mount rubber manufacture

[cardiffrob]

Hopefully this helps explain Plan B. Ends welded to the box section and then the top cut off with a slitting disk. I now need to drill holes for the mounting studs through the base of the trough and hang the 5mm top plate from brackets to be welded on each end. Once the rubber has set it can have the ends cut off the trough and 4 completed rubber mounts can be separated by hacksaw. The 5mm plate needs the holes drilled and something done to the bottom of it to hold it more securely in the rubber, as per earlier comments.

 

[colnerov]

Hi, You could just tack weld the centre plate to the closed ends of the trough, if you're going to cut the closed end off it will separate it. You could drill holes in the centre plate so the rubber flows through it or weld short pins through them giving a better mechanical attachment to the rubber. Looks good so far.

Colin

 

[tinman123]

this ill be interesting rob.

if you dont mind me saying,
id of been inclined not to have cut the top of the box there so wide, i think id of left a step in on both sides of maybe 10mm or so to give the rubber some hold.
then id consider running a nut up on a cup head bolt to the head of it and tighten it up, pass it through the box and run another nut up on it to hold it in place, remove that when your fitting it.

id also be concerned about the smoothness of the inside of the box, id be inclined to sand blast it or something to give the rubber a key.
and as for the flat plate, id probably just weld on a bit of flat to the bottom of it if you have the room to make it the shape of a T piece, or maybe drill a few holes in it and put pins in it to give it grip again.

 

[cardiffrob]

The company who have offered to perform a rubber pour say they blast it in pieces before adding the bonding agent and then pouring so it will be abraded before the materials go in. I can't change the size of the hole in the top or it won't look original enough to pass scrutiny by the prospective owner. All mods need to be hidden. Holes in the centre plate sound a good idea!

 

[tinman123]

aha, i thought maybe you were going to pour them yourself.
still, an interesting project, the longevity will be the one,
but as we said about the Titanic, she was grand when she left here...

 

[cardiffrob]

5mm plate, holes drilled and bottom edge sliced off for re-welding to make a 90 degree lip. The long legs at the ends, when finished, will hold the plate so that the holes are at the right height. I can get 4 mounts made in here in one go and then slice them up. More holes to drill in the plate to let the rubber join through it.

 

[colnerov]

Hi, good job, I can see that lasting longer than original.

Colin

 

[tinman123]

make sure and tack the flat plate in before you send it off, the next man mightnt be as worried about it as you are when he goes to pour it.

 

[Pete.]

Rob is there any reason why you aren't just buying some pourable ShoreA60 and making them yourself?

http://www.mbfg.co.uk/polyurethane-rubbers/pt-flex-60-rubber.html

 

[tinman123]

Rob is there any reason why you aren't just buying some pourable ShoreA60 and making them yourself?

http://www.mbfg.co.uk/polyurethane-rubbers/pt-flex-60-rubber.html

this bit would bother me, not exactly reassuring for an engine mount application, on the outside at least but i know nothing about the stuff sither, just a reading observer when it comes to diy rubber compound.

which has been developed specifically for prototyping and model making applications

 

[Pete.]

It's just rubber, and further down it does say:

It is excellent for casting decorative objects, production parts....

 

[tinman123]

indeed it dose, i cant argue about it tbh as ive never used it.

 

[cardiffrob]

I spoke to them on the phone a couple of weeks ago. MB Fibreglass, Belfast, t.a. MBFG. The stuff they sell is mixed at the factory with release agents so whilst it is ideal for casting stuff it is totally unsuitable for making rubber/poly mounts, according to their company expert.

As for tacking the plate in before sending it, I can't because they need to get it apart to abrade the internal faces and paint them with their magic fairy dust compound before the rubber gets poured or the liquid won't bond properly, hence the small bolts used for alignment. [Ooops not shown in that picture.]

 

[tinman123]

aha, if you can bolt it together for pouring then your laughing.
a bit more work but a good plan.

 

[cardiffrob]

Just need to drill some holes in the bottom of the trough and weld in some studs.

The ends will be cut off to separate the 4 finished mounts. If this works I'll be able to make the whole lot from several feet of material to knock up a much bigger batch.