Time for Ringmaking-Take2. I am now going to make 4 more rings using the Trimble? method. I do have a 0.020" slitting saw. So---the rings will be turned to (3.142+.020)-3.142=1.006" o.d. and 0.898" inner diameter. This will give an inner diameter the same as rings I have purchased form Debolt. They will be cut to 0.063" thick. Instead of being broken, these rings will be cut using my 0.020" slitting saw. No farther work on cleaning up the i.d. nor the o.d. nor the thickness, until I have spread them individually over a 3/16" piece of steel inserted into the sawn gap and heat treated them to cherry red and then allowed them to air cool. Then they will be polished to 0.062" wide and cleaned on a sheet of emery paper on a flat surface, then positioned in the cylinder bore and if needed the gap will be filed to give a 0.004" wide gap.
I know this is going back a ways (post #57) and please don't take this criticism of what methods & effort you eventually employed. But the Trimble? (question mark) is appropriate because its just not the Trimble method on multiple fronts. I'm not saying what's right or wrong, just reading the SIC article and making the comparison.
- nowhere does Trimble mention a slitting saw. He goes into quite a bit of detail saying consistent success eluded him until he eventually settled on cleaving the rings. Basically trying to get as close to a zero width part such that the rest of the procedure & heat setting apparatus would ensue with a known reference. The only gap treatment prior to heat setting was minor clean. Basically eliminating a micro carrot of material stuck on one side of ring which originated from corresponding carrot hole on other side. The protrusion had to be levelled so the two faces aligned properly to the dowel diameter as intended.
- other folks have offered input as to how to compensate the OD if a slitting saw is uses. No comment because of many examples where it obviously works. I'm just saying it wasn't in Trimble's method. The post heat treat gap width calculation is defined in the writeup.
- the pre-heat set Trimble ring OD & ID are fully defined in his description. The OD has a very minor +tolerance but he says toss any rings that come out under bore B. The ID is a calculation result of the T/B ratio, not related to the piston or anything else. ID = OD - 2*T
- re heat set, there is an interesting chart in the article (Fig-12). It took me a while to digest it & anyone please comment if I'm misinterpreting. He is showing the effect of supporting the open ring on a rectangular spacer block as opposed to on the dowel. However the gap opening between the two setups are identical. The difference is that the ring is supported on its inner corners in the case of rectangle plate vs. resting on the ring neutral axis tangent point in case of dowel spacer. The resultant plot then shows the X-axis around the bore and Y-axis delta R (radius in inches) deviation to the bore. The rectangle spread curve deviates as much as 0.0035" from bore wall vs. the dowel based curve which he is saying is the theoretical perfectly circular curve plot (consistent radial seal). '
the dotted line shows the same data for the ring spread with a spacer as in fig 11, it has the proper curvature in two places where the dotted and solid lines cross, Everywhere else the curvature is too large or too small. Particularly disturbing is the area near the gap where the curvature is less than the cylinder curvature, There is no way for this area of the ring to touch the cylinder when installed because it is more sharply curved than the cylinder itself. So this seemingly minor subtlety with the same effective opening results in basically a barn door sized opening relative to high pressure gas. The significance of varying the dowel diameter would be greater still, which is why he provides the T/B vs D/B constraint chart.
Also note, the calculated dowel diameter is not actually the maximum opening for ring during heat set. I had to stare at those unfortunately teeny SIC diagrams & re-read the verbiage to realize - its the combined effect of his mandrel diameter, dowel diameter & their relative spacing on the fixture that positions the ring with the correct opening with dowel contact at the neutral axis as described above. And this fixture is intended to assist so its hard (er) to misalign ring in spread mode.
