Cedge
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- Jul 12, 2007
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Ok... you won't see it in any machinist manual. It's even a little hair brained and probably worth a good laugh, but a 5 year old just might have saved my bacon with Pla-doh. Yup... that brightly colored, smelly, dough like concoction that gets on everything within a hundred feet when they play with it.
As I've mentioned before, the Elbow engine has been defying all efforts to eliminate a persistent stiff spot . With 10 piston ends, 10 cylinders and 10 decorative balls that potentially limit adjustability, there are quite a few possible combinations to try when looking for a bummed piston set. Add in the fact that they all look alike and... well you get the picture. It's easy to lose track of what you've done in a real hurry.
My 5 year old grandson was over for the weekend and, as is his habit, he broke out the Play-doh. While he played with it, he pressed a number of objects into the goo, over and over. I wandered into the play room this morning and saw he had once again left some out of the container and it had dried to a solid imprint of his efforts. I was about to throw the small dried pancake away when a bell went off in my head.
I swiped a bit of the stuff, pushed it into a plastic container lid, put this into a plastic bag and rolled it out smooth with a water glass. I then located a piston set that seemed to be performing well and pressed it into the Play-Doh. When removed, it had made a perfect impression of the piece.
I then carefully laid each piston set into the imprint for comparison and immediately noticed a variance of about .020 in. with one end of the set. Each set showed the same variance. When checked with a depth gauge, the piston ends were all evenly matched in length. It took a couple of minutes to digest what I was seeing.
I compared the pieces again, but this time I placed the set in the mould and then reversed them for a second test fit. The variance was definitely present in each set, but it was uniform across the group. I began looking for a reason for this oddity. It was found in the bend of the elbow. I apparently missed the center point when I built the bending jig I used. It was ever so slight a miss, but enough to add .020 in to one end of the piston sets.
For the heck of it, I arranged the pistons on the work table so that I knew which end was a little short and began replacing them into the cylinders. I chose to place the long end in the upper drum. Since my adjustment point is the lower drum, I can easily move the pistons in and out to make the required adjustments.
Things feel much better and I'll be putting air to the little devil again this evening. Wish me luck.
I think I'll be keeping a bit of Play-Doh or modeling clay around the shop....LOL.
Steve
As I've mentioned before, the Elbow engine has been defying all efforts to eliminate a persistent stiff spot . With 10 piston ends, 10 cylinders and 10 decorative balls that potentially limit adjustability, there are quite a few possible combinations to try when looking for a bummed piston set. Add in the fact that they all look alike and... well you get the picture. It's easy to lose track of what you've done in a real hurry.
My 5 year old grandson was over for the weekend and, as is his habit, he broke out the Play-doh. While he played with it, he pressed a number of objects into the goo, over and over. I wandered into the play room this morning and saw he had once again left some out of the container and it had dried to a solid imprint of his efforts. I was about to throw the small dried pancake away when a bell went off in my head.
I swiped a bit of the stuff, pushed it into a plastic container lid, put this into a plastic bag and rolled it out smooth with a water glass. I then located a piston set that seemed to be performing well and pressed it into the Play-Doh. When removed, it had made a perfect impression of the piece.
I then carefully laid each piston set into the imprint for comparison and immediately noticed a variance of about .020 in. with one end of the set. Each set showed the same variance. When checked with a depth gauge, the piston ends were all evenly matched in length. It took a couple of minutes to digest what I was seeing.
I compared the pieces again, but this time I placed the set in the mould and then reversed them for a second test fit. The variance was definitely present in each set, but it was uniform across the group. I began looking for a reason for this oddity. It was found in the bend of the elbow. I apparently missed the center point when I built the bending jig I used. It was ever so slight a miss, but enough to add .020 in to one end of the piston sets.
For the heck of it, I arranged the pistons on the work table so that I knew which end was a little short and began replacing them into the cylinders. I chose to place the long end in the upper drum. Since my adjustment point is the lower drum, I can easily move the pistons in and out to make the required adjustments.
Things feel much better and I'll be putting air to the little devil again this evening. Wish me luck.
I think I'll be keeping a bit of Play-Doh or modeling clay around the shop....LOL.
Steve