T head engine by Brian

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djswain1

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I just ordered a set of three plates for my rotary table. Is there a chart available which would give settings or some type of calculator or a formula? So far I have not found anything. I can find some for 40 turn tables but mine is 90 turn.
Brian great Job you are doing there yet again.
I hope you don't object too much to these replies to Gordon in the middle of your thread.

Gordon l used my "new to me" rotary table and dividing plates for the first time at the weekend.
It came with some instructions and has the 90:1 ratio. See the attached pictures.
Cheers, Dave.
 

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Brian Rupnow

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Things are going to slow down for a little while. One of my old customers has come foreword with a request for some new welding fixtures for one of the big three automotive companies. It's design only stuff. Fabrication will be done elsewhere. I'm not sure just how much work there will be, but probably not much.---It would be nice if there was a couple of weeks work---that would buy me a new metal cutting bandsaw. My current bandsaw is an old woodcutting saw that I modified to cut metal. It works, but it is painfully slow.
 

Brian Rupnow

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The welding fixture is completely designed and sent to my customer, who has to go to his customer for "design review". After that has happened I will complete it and make detail drawings.---Now--Back to my own stuff. I finished the welding fixture design about noon today, and spent the rest of the day machining valve cages. In a perfect world, they would be a press fit into the head. In the real world, you can't press them too hard because they are made of brass. So, they are coated with #638 Loctite and lightly pressed into place with my shop vice. After they set up for 24 hours or more I will drill the intake and exhaust port thru the cylinder head and the valve cages at the same time. I have not used my special valve guide cutting tool yet to prepare the seats to mate with the valves. That is just about the only thing left to do to the valve cages. I will make the valves later today or perhaps tomorrow. I did stop by my metal suppliers today and picked up a foot of 1 1/2" diameter "stress-proof steel to machine a one piece crankshaft from.
 

Brian Rupnow

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Todays nifty trick was to machine a pair of tappet guides. They set between the 50 tooth gears and the sides of the engine frame. They have a 7/8" clearance hole on center to clear the cams, and there will be a 5/16" i.d. sintered bronze bushing pressed into the hole in the top of them to guide the tappets which ride on the cam. The cam is attached to the side of the 50 tooth gear.
 

Brian Rupnow

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I had to take my chainsaw over to my oldest son's place and play "Johnny Lumberjack" this morning and take out a couple of big trees for him. This left me with a bad case of "lazyitis" this afternoon, so I made two parts for my engine that didn't require a lot of thought. The brass part is the adapter for the Traxxas carburetor, the aluminum piece is the exhaust.
 

Brian Rupnow

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I ran into something a bit strange yesterday. When I threaded the ends of the exhaust and carb adapter for the engine yesterday, the parts were held in the lathe chuck and the die was held in a collet in the tailstock chuck. No problems were encountered, I even ran a standard 3/8"-16 nut up the thread to ensure that everything was Kosher. When the cylinder head was tapped 3/8"-16 it was held in the milling machine vice and threaded by hand with a tap and standard handle. After screwing things together yesterday afternoon, they were crooked!! It doesn't show in the picture I posted, but they were quite visually crooked. I didn't want the Loctite to set up, so I disassembled things. This morning I held the cylinder head in my mill vice and a tap in the milling machine spindle and turned the spindle by hand, and the tap was cutting metal. I ran the tap in until it bottomed out, removed it, and cleaned up the ends of the cylinder head. I then held the inlet (carb adapter) in the chuck of the milling machine, applied a bit more Loctite and turned the spindle until the shoulders on both pieces were touching each other. I must have had the tap turned at an angle when I first threaded these parts. I would stand and deny that I would make such a dumb mistake, but I can't figure out what else it could have been.
 

CFLBob

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Thanks for the confession. I personally learn more from reading about mistakes than just marveling at well-machined parts.

Do you think something like one of those tap guides that's basically a clearance hole in piece of thick stock to keep the tap perpendicular would help? Those seem to depend on the work having nice flat surfaces to sit it on. You mentioned the cylinder head being on the mill the first time you tapped it; would something held in the spindle to indicate being perpendicular help?
 

Brian Rupnow

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It hasn't been a horrible morning, but it sure as heck hasn't been productive. I have one valve to show for it. Beside the valve sets a piece with a 0.1875" hole reamed thru it to check the valve stem for when it is exactly the right size. I can't even begin to tell you why it took so long, but suffice it to say, I've never sanded on anything in my life as much as that valve stem to bring it down to size. I did use a live center in the tailstock to keep the outboard end from flexing while the valve was machined. Maybe tomorrow I'll get lucky and make another valve.
 

Brian Rupnow

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Bob--Most times, if the tapped hole is deep enough, the tap will pull itself straight as it goes in. These holes were very shallow, and consequently they stayed a bit crooked. I never use tap guides, and I seldom put a tap in the mill quill. Sometimes that comes back and bites me.
 

CFLBob

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After breaking off too many taps I started trying to tap on the mill, usually with the drill chuck holding a 1/8" dowel pin. That size because it fits in the tap wrench when its holding smaller taps and it will touch the top of the tap. Most of those have a square section with a point in the middle. I've used that to make sure it stays perpendicular for the first couple of turns. It sounds like this might keep me safe.
 

Richard Hed

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I ran into something a bit strange yesterday. When I threaded the ends of the exhaust and carb adapter for the engine yesterday, the parts were held in the lathe chuck and the die was held in a collet in the tailstock chuck. No problems were encountered, I even ran a standard 3/8"-16 nut up the thread to ensure that everything was Kosher. When the cylinder head was tapped 3/8"-16 it was held in the milling machine vice and threaded by hand with a tap and standard handle. After screwing things together yesterday afternoon, they were crooked!! It doesn't show in the picture I posted, but they were quite visually crooked. I didn't want the Loctite to set up, so I disassembled things. This morning I held the cylinder head in my mill vice and a tap in the milling machine spindle and turned the spindle by hand, and the tap was cutting metal. I ran the tap in until it bottomed out, removed it, and cleaned up the ends of the cylinder head. I then held the inlet (carb adapter) in the chuck of the milling machine, applied a bit more Loctite and turned the spindle until the shoulders on both pieces were touching each other. I must have had the tap turned at an angle when I first threaded these parts. I would stand and deny that I would make such a dumb mistake, but I can't figure out what else it could have been.
Many years ago (probably before you were born) I happened to have bought a thread gage from Sears. The 3/8ths - 24 was the single gage I used the most. I kept getting the wrong reading and was wondering what was wrong to the point of I started kicking things. This went on for months. When I used someone else's gage, there didn't seem to be a problem but I didn't really realize what was happening. I thot it was my own mis use or misteaks or wat ever. Well, one day I happened to have another thread gage and I compared the two 3/8-24 gages. The Sears one was WRONG! I was so shockt that I recheckt it on other gages. The other gages all agreed with each other but not the Sears one. so I tood the set back to Sears and the fellow there did not believe me, so I demonstrated it with his other, in store gages. He, like myself, could not believe it. Sears had somehow gotten a gage that was stamped with "24" on it which was incorrect. After he realized that I was correct, he handed me a new one and took the old one probably to send to quality assurance.

My point is that "sh*t happens" and some times it's simply inexplicable. You already know this, of course, but some times it's misery loves company. LOL
 

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