So I'm considering the feasibility of casting these in either investment or shell using al-bronze. Ideally with the hex hole in place, can be broached clean afterwards. The other holes can be machined post clean up. I can use the originals as patterns and the minor shrinkage should't be an issue. I would hope to cast 6 or more per mould to be economic. Any ideas how much shrinkage I can expect with al-bronze, any pointers or suggestions? I'm not geared up for either process yet, just chunking around ideas.
I'll try and get some pattern vs al-bronze casting measurements tonight if that would help. Right now I just have pix for comparison, note the extent to which the handle did not fit in as far as the coreprint made from an almost identical handle: Risers in C954 Al bronze also show much more piping/shrink than in wheelium Al. FWIW. Jeff
Thanks Jeff, I didn't want to disrupt your axe thread. These parts wear and suffer stress cracks (poor design) If you have an idea on shrink much appreciated, otherwise I should just give it a go. Now for David to tell me investment and our 'top gun' to say shell..... either way I think they are too small to not consider vac cast
The standard parts were aluminium, then they went die cast, these are machined replacements. They suffer with stress cracks and wear on the holes that screws up the tuning. (It's a pedal steel and there is a huge amount of force on them from the knee levers) I thought an al-bronze would have better strength (along with an added generous fillet in the leg) and better wear. maybe I can get that from everdur but i'm out in the cold here with little experience of either materials.
Didn't get to measuring that shrink last night, sorry, I wound up having to go out and never made it out into the shop. Tonight for sure... Jeff
No worries Jeff, I'm not in a rush. My father is hand machining these bits very slowly and I thought maybe there is another route.
Well, I used some cheapo plastic calipers I don't really trust to take some measurements of casting and pattern to compare. Casting works out to 96% of the size of the pattern when I average out my calculations. Plus or minus about 96%... Jeff
I said it was an unreliable measuring device, right? Plus I had done some grinding and sanding on the casting already. Better off just looking it up, I guess. Hey, I tried... Jeff
Thats ok, Fifty lashes should make up for it I still question the 2% I would have expected it to be lower in the <1.5% range. Im not sure that .5% would make that big of a difference on a 2" long part anyways...
Thanks for looking Jeff, ignore the reprobates! The only part that worries me is attempting to include the hex in the investment and hot tears (that and I have no damn idea what I am doing away from sand cast stuff). Turns out there are at least 6 different types of these 'bell cranks' all with wear and fracture issues. These pedal steel guys are very serious about the tuning on their kit (I was dragged up listening to country music and I hate the damn things but each to their own......)
What materials are they made from? all aluminum? The more I think about this project the more I feel that casting may not the best method of reproduction. Maybe its better to machine them from alloy steel and nickel plate the pieces.
Some were aluminium, then Sho-Bud moved to a die cast Zinc/al alloy. Machined aluminium parts work well as replacements but they still suffer wear spots where the rest of the mechanism grinds against the crank in a very small area. The chrome plate holds up for so long and then once the surface is breached everything goes to pot. It may not be a sensible option to cast them and I may not even have the time to give it a go but thought I'd throw it out there as a bronze may well take the wear issues in the right direction.
