Here are a few files I made up on 3D printer while setting up carbs, 7mmp1.stl is a 7mm height gauge for floats together a 30 degree setting piece both printed on PLA also a 4 hole gasket for the fuel taps on MC19 you will also need a M3 Tap and 2 3mm x 12.5mm screws to replace rivets. This is printed from TPU. The STL (3d Print files are in a zip as "STL" file type is not allowed.
Good stuff Brian. Have you tested the TPU in petrol. My first choice would be Nylon or PETG for parts exposed to petrol. I printed some small velocity stacks for some MC19 carbs (used on my RC162 tribute bike) in Nylon. Nylon is a bit of a pig to print. In hindsight, PETG might have been the better choice. Peter.
The TPU has been in petrol for 2 weeks and no change in size or feel, you can still see the printer marks. I printed at 100% fill and still flexable enough to feel more like butyl rubber. PETG is no good I saw a video where someone made a little bottle from PETG the filled it with petrol, it became porous (petrol seeped out) and brittle. TPU may be a little soft for stacks, I am printing some parts in carbon fibre PLA for a speedo bracket for a 1934 BSA and they were easy to print and appear to be very strong. I do worry about PLA for velocity stacks however because of heat and I am setting up to do some aluminium castings for some custom parts including the speedo brackets using the PLA prints for a pattern.
We did some testing with a little PETG cup and left it in petrol for 1 month with no noticeable issues. It should be fine for stacks. PLA is definitely no good where heat is involved. PLA is good for patterns (lost wax style). We have been using PETG to make tooling for carbon fiber parts casting as well. I will be interested to know how you get on with your aluminium cast parts. Are you still going to do a sand box setup with the PLA part/pattern in the middle. I wouldn't mind trying some metal casting at some point.
Yes greensand PLA pattern still trying to get a good mix for greensand using ground kitty litter and river sand but will buy some very fine bentonite and <60mesh sand to try.
Speedo bracket is sandcast as it was done that way in 1930 the mold is fairly simple so doesnt need the complexity of lost PLA with investment plaster. These are PLA carbon fibre.
