Where to source bronze or brass plate

I've suffered a small setback in my effeorts to build my gearbox design. The gear selector forks are supposed to be made from bronze. I asked for a quote for their production and supplied a suitable drawing of the largest of the three. Unfortunately the casting producer has to sub-out the 3D printing of the moulds. The castings would have cost about £65, which I thought was very reasonable, but the mould printing was going to add another £135 or so to the cost! I can't justify that outlay, so I'm thinking that I might have to carve them out of bronze or brass plate. The finished articles are 10mm thick, so we're talking seriously thick plates here. Or I might get away with two brass plates of 5mm, soldered together. I can't go any thinner, or the joint lines will interfere with the machining. Any ideas, anyone? Or alternative suggestions. I could easily fit them on a plate 170mm x 60mm, as below:

John

P.S. The design has changed, slightly since I drew this, but you get the idea.

Get a bit of hollow cast bronze and make the "C" shapes, looks like you may get two from one piece and the third from a smaller dia. Then Silver solder on the other bits.

You could try Mallard Metals. They don't list Bronze flat, but they do say contact them if it's needed.

Brass I'm sure they will stock

**LINK**

Following on from Jasons suggestion, I happened to be on the Metals4U site and I had a look, they do 660 tube in a range of sizes up to 4 inch O/D with various wall thickness and PB1 up to 6 inch. I thought they had a minimum of 50mm cut length but it looks as if with the larger bronze tube they will cut even shorter.

Depending on size M-machine do 2" x 1/2" bronze flat and can cut blocks from 11mm GM sheet. They also do the hollow bronze and GM cut to whatever length you want.

This might be daft, if so someone will let me know, but can you machine them from wax, then send the wax bits to a lost wax casting man? Or even from polystyrene (they might be a bit small for that, but it works for full size loco cylinders) see **LINK**

Many thanks to you all for the input. I'll follow them in turn. I particularly like Jason's idea of utilising tubing. That'll be the most materially economic way to do it, I think. I'd only need to get a gas torch and learn to silver solder then!

I'll let you know how I get on.

John

Hi Duncan

This gas turbine inner section NGV machined as a tryout
from prototyping wax could be used for casting purposes
if tided up a lot ,as with all castings the pattern is the part that
takes up most time,the second photo is some model engine
parts from the early 90's ,the exhaust stub the semi-circular
part with the slot through the centre required the complicated
mould seen here top left .

John

Does it really need to be 180 degrees? Would 90 do? Then the bearing part could be machined from a bar with a bit more waste. Perhaps it could be bent from bar to get part way there. The mounting part doesn't need to be bronze.

I know you said you have changes the drawing now but if optimising material usage saves money the layout you show could be much improved (as long as its being cut with steerable blade like a fretsaw, but much more manly.

If these forks sit in grooves of gears that are close fitting on the shafts/splines then would just say 120 degrees of the circumferencial engagement rather than 180 be OK, would save even more material.

Ian P

Your price for having castings made seems reasonable.

Why don't you make the patterns from wood which is the traditional way of making them. Use plywood, craft wood, plastic or any other material which you can cut and shape. Cost of a pattern could be zero.

Paul

Ian P/Paul,

Yes, I'm sure that I can optimise the layout to use less material; the drawing was just one I bashed out to illustrate the basic shapes and scale. You're right about the angular dimensions, too. I'll bear that in mind.

I have some aluminium plate 12mm and 10mm thick, so I'm now considering making them out of these in the first instance. Firstly, it will let me practice the machining sequences and by making them 2% oversize, I could use them as moulds later. More thought required. In the meantime, I've got more than enough gear and spline cutting to keep me occupied!

John

Make up a simple pattern to give you a few ingots to machine the parts from and get it cast out of bronze .

Edited By XD 351 on 19/09/2019 00:32:31

What's the gearbox for? How much load? What speeds?

Plenty of motorcycle gearboxes use steel selector forks. Usually hardened but presumeably to a lesser degree than the hardened gears they engage with. The selector forks are only under load when shifting gear. Otherwise they are merely a placeholder and under very light load.

So you could get some 10mm thick steel gauge plate and cut the parts out and machine them then harden and temper them.

Or go to a motorcycle wreckers yard and get some ready-made selector forks out of a trashed gearbox.

If the central one could have a fractionally shorter arc they would all come out of the 2" x 1/2" bronze bar I suggested from M-machine if your sketch is 60mm high. and no need for any soldering.

M-machine can also supply 3/8" and 1/2" thick Phosphor Bronze PB 102 sheet so you could probably have a piece cut to the size that suits you if required/preferred.  And, referring back to your original post M-machine can also supply brass flats 1/2" thick up to 6" width cut to length required.

Regards,

Phil

Edited By Weary on 19/09/2019 09:02:44

I have taken on board all the leads and suggestions and have decided on the M-Machine metals route, using ½" x 2" bronze bar. By also reducing the angular bearing arc to 120°, I can further reduce the waste material. I don't want to go any less, for aesthetic reasons. It just doesn't "look right".

Thanks, once again, for everybody's input. I think we can consider the matter closed.

John

And just to keep you up to date, the bronze bar has been ordered and will be in my eager hands before too long, I hope.

John