Dang--Ya gotta love it when a plan comes together---
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Double acting Double Oscillator
- Thread starter Brian Rupnow
- Start date
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One piston fits really good, one is a little looser than I like, but when I put in a couple of v shaped oil grooves on each piston, that will displace enough material either side of the V to make them fit perfectly, in fact they might have to be "Wrung in" again to get them into the cylinders.
I was wrong about that. Putting the v-grooves in the cast iron pistons didn't raise a "berm" of displaced material on each side of the v-groove like it does when working with cold rolled steel. On the cast iron the v is cleanly cut but no metal seems to get displaced on each side.--I live---I learn.
I was wrong about that. Putting the v-grooves in the cast iron pistons didn't raise a "berm" of displaced material on each side of the v-groove like it does when working with cold rolled steel. On the cast iron the v is cleanly cut but no metal seems to get displaced on each side.--I live---I learn.
I decided not to solder the piston rod ends in place on the rods. The holes in the piston rod ends were reamed and provided a good "fit" for the rod end itself, so I used some 638 Loctite and when it had set up I cross drilled with a 1/16" drill and loctited in a 1/16" mild steel pin. A great tip here that was given to me by someone else--It is difficult to buy 1/16" diameter cold rolled steel rod, but the welding supply store sells 1/16" diameter steel welding rod that seems to be perfect for jobs like this and also on pinned crankshafts.
It has been suggested by folks on a different forum that heating cast iron pistons to "bright orange" and then letting them either air cool or quenching them in oil (There is some confusion which) will make the piston "grow" a little bit in diameter. I have never heard of this, but am conducting a test to see if there is any truth to the suggestion.
Okay--Here we have two rather dirty cast iron pistons that were made and only used for about half an hour. They have never had any kind of heat treat from me. One will be heated to "orange" and then dropped into a container of oil. The other will be heated to orange and left to air cool back to ambient temperature. I have measured multiple positions around the diameter on both pistons and they are all 0.875" +/- .0005" diameter.
Okay--Here we have two rather dirty cast iron pistons that were made and only used for about half an hour. They have never had any kind of heat treat from me. One will be heated to "orange" and then dropped into a container of oil. The other will be heated to orange and left to air cool back to ambient temperature. I have measured multiple positions around the diameter on both pistons and they are all 0.875" +/- .0005" diameter.
The results are in. The piston which was heated to bright orange and then allowed to air dry did not change in any way. The heating and air cooling had no effect whatsoever.---BUT---The piston that was heated to bright orange and then tipped into a can of oil has grown, and uniformly measures 0.876" , measured at multiple spots around the piston. So, yes, about 0.001" of growth on the 0.875" diameter. I will set the "grown' piston up in my lathe and turn some off the diameter to see if the machineability has been altered by this test.
The third test has just been completed. I burned up two drill bits trying to enlarge the center hole in that "grown" piston, to mount it on an arbor. So--not only does the heat and quench make the piston marginally larger, it makes it harder than the devil's horn. Test is over. I conclude that "growing" a cast iron piston is possible, but not advisable because the iron becomes super hard and can no longer be machined with conventional tooling.---Brian
I've been faffing about all weekend trying to convince myself to make both of the crank arms out of steel. Not difficult, just an awful lot of offset turning in the 4 jaw chuck. I chased my tail round and round and finally decided to make them a three part assembly. Probably use aluminum for the slime green hub and brass for the arm itself, with three #4 shcs holding everything together and a steel shaft press fitted into place..
I tried to delete the previous post, but this new hosting software doesn't seem to allow me to do this.
I tried to delete the previous post, but this new hosting software doesn't seem to allow me to do this.
Anatol
Well-Known Member
Thanks Brian, interesting test. Coincidentally I was watching one of a series vids on utube where guy is doing a competent job (to my eye) casting and building a quite big engine. He made cast iron rings and heated and water quenched to both spring out and harden.
After a "machining free" weekend I decided to build some crank arms. I could have used the four jaw chuck in my lathe and turned them from solid (not including the rod journal) or I could make them from built up pieces. I decided to make them "built up" assemblies. Honestly, I think it would have taken about the same amount of time either way. I've been dragging my feet a little on the cylinder assemblies because I need a couple of rather "special" set-ups" involving my rotary table and mill to put a partial radius on the center side of the cylinder caps. Will probably get to that tomorrow.
What a monster!!! With the cylinders and crank arms finished, there isn't much to do now except the angle frame and the flywheel. There are very few "small bits" on this engine anywhere.
Here is a rather interesting video showing how I take any "sticky spots" out of an assembled cylinder and piston assembly. No lapping compound is being used, just 30 weight motor oil.
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Remember that piece of 2" aluminum plate from way back at the beginning of this thread? Today it's slowly becoming a 1.6" thick flywheel. The key word here is SLOWLY. There's a lot of turning in that 6" dia. flywheel.
A slight change to the game plan this morning. I didn't like the flywheel being so far up in the air, and I really didn't like having to work with the frame angles when everything was going to be at such strange angles to machine them. So--this morning I spent a couple of hours bringing the frame around to a more conventional setting. Nothing is lost, but it should be a bit more stable when running, and a lot more easy to machine the frame.
Here we have a rather nasty "in process" shot of the 7/8" holes being drilled around the flywheel, and a family shot of all the completed pieces. That flywheels borders on the ridiculous, but it's what I wanted. I have to figure out a way to deburr the 7/8" holes, and then it's time to move into working on the angle frame.
The ultimate evil deburring tool. Some strange tapered thing I inherited from my father, held in a keyless chuck that I repurposed from an old 3/8" drill.
By redesigning the frame, it not only simplifies the construction of the frame pieces, it also gives me a nice vertical surface on which to mount the intake/exhaust manifold.
After what seemed to be an amazing amount of band sawing and milling, the 6 x 6 x 1/2" aluminum angle has been reduced to two angles 4 1/2" x 2.4" x 1/2" x 7 3/4" long. They are as identical as I can make them, and anything done next is going to make them right and left hand. I am off to a party this afternoon for my old electrical engineer friend who turns 60 years old today. He has been working in Germany for the last 15 years, and just returned to Canada last week. I haven't been to a party in years so I'm looking forward to this.
Brian. Just an idea: instead of porting in the end face of each angle, the central spacer block could have porting in it, making the external pipework tidier - no need for tees & elbows. Could build in a reverse control as well.
Also, I suggest a couple of drill-rod dowels in holes reamed through all three parts to ensure proper alignment of the crank bearings on re-assembly.
Also, I suggest a couple of drill-rod dowels in holes reamed through all three parts to ensure proper alignment of the crank bearings on re-assembly.
Trying to post a pdf of a cad model of the spacer block porting idea. Let's see if it works.
Edit: not really what I was trying to do, but you can open the file.
Edit: not really what I was trying to do, but you can open the file.
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Good wife and I drove down to the "big smoke" (Toronto), partied like it was 1999, and got back to Barrie like good old geezers before dark. Great time was had by all, my electrical engineer friend plans on returning to Germany for six more years. You can retire with a pension at sixty six in Germany. Then he is coming back to Canada for his retirement.
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