Author Topic: T head engine by Brian  (Read 8154 times)

Offline Pete49

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Re: T head engine by Brian
« Reply #165 on: September 12, 2021, 04:17:27 AM »
Looks good with the paint job as well. Nice little goer.
I used to have a friend.....but the rope broke and he ran away :(....Good news everybody I have another friend...I used chain this time :)

Offline Roger B

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Re: T head engine by Brian
« Reply #166 on: September 12, 2021, 02:07:35 PM »
Very nicely done  :praise2:  :praise2:  :wine1:

I tried some of those aluminium soldering/brazing rods with success. There is quite a small window between the flux and the rod melting and everything melting  ::)

https://www.modelenginemaker.com/index.php/topic,9433.0.html
Best regards

Roger

Offline steamer

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Re: T head engine by Brian
« Reply #167 on: September 12, 2021, 02:15:18 PM »
It's a runnah!    Nicely done Brian!

Dave
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Damned ijjit!

Offline Brian Rupnow

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Re: T head engine by Brian
« Reply #168 on: September 12, 2021, 03:43:25 PM »
Question--do you have to have a special tool to insert helicoils? I have a couple of 10-24 threaded holes in my aluminum cylinder head that are getting kinda funky. I can buy a bag of helicoils for $12, but I I buy a "helicoil kit" the price shoots up to $45

Offline Roger B

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Re: T head engine by Brian
« Reply #169 on: September 12, 2021, 03:47:22 PM »
The outside thread may be special  :headscratch: The inserting tool just has a slot in the end to drive the tang in the helicoil so it tends to 'shrink' it as it goes in.
Best regards

Roger

Offline steamer

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Re: T head engine by Brian
« Reply #170 on: September 12, 2021, 03:48:09 PM »
I have been successful using just a screw to insert them in a pinch.    You could try it that way and buy the tool if you need it
Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline Brian Rupnow

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Re: T head engine by Brian
« Reply #171 on: September 12, 2021, 09:13:55 PM »
After painting and reassembling the engine, it looks lovely but it won't start. It won't start because it has lost compression at the valves.
It started and ran fine earlier this week. The painting process didn't involve any of the things that would make the valves leak.  Valve timing and ignition timing have been checked, and they are "spot on". The only difference between this engine and other engines I have built is the exceptionally long guided area of the valve stems. I have a theory that the longer contact area is creating enough friction on the valve stem to keep them from closing properly. First and easiest thing to try will be stronger valve springs. If that doesn't fix things, then my other idea can be seen at the right hand valve in the drawing. The lower portion of the guide area of the valve cages would have a clearance from the valve stem, and an inserted, concentric supplementary guide Loctited into the very bottom. This may well be the reason that Vederstein couldn't get the valves to seal on the t head engine that he built.

Offline john mills

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Re: T head engine by Brian
« Reply #172 on: September 12, 2021, 11:27:20 PM »
to fit the helical you need the tap it is the same pitch but is a  size so when the insert screws in the inside is the
correct size for the original thread.so the hole has to be retapped with the helical tap.then the insert can be screwed in by a tool with drives it in by the tang  the tool has a slot and is of a size the insert fits over and the tang fits in the slot .when in the tang is broken off by bending .sometimes a light bump on the tang will do
some times the tool will grip sufficiently to bend enough up and down   and it should fall off.
The kit should have the helical tap.
John

Offline Brian Rupnow

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Re: T head engine by Brian
« Reply #173 on: September 14, 2021, 09:33:31 PM »
I dipped into the Rupnow fortune today and bought a 10-24 Helicoil kit which comes with all the necessary drills, taps, etcetera and about 40 inserts in different lengths for $116.00. While I was picking up the kit, I picked up some very heavy, bull-doggy looking compression springs to be used as valve springs. The valve springs I have on the engine now are 0.026" diameter wire size. The new ones I bought are 0.049" wire size. They are also larger in overall diameter, so tomorrow I will machine new valve cups that go on the valves to center the springs. This business of valves sealing one day good enough for the engine to run, and then not sealing the next day is ridiculous.

Offline Brian Rupnow

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Re: T head engine by Brian
« Reply #174 on: September 15, 2021, 09:13:56 PM »
The Helicoils worked great. I have never used them before and I must say, they work fine and don't require a lot of work to use them.  I did machine new spring cups and install them and the heavy valve springs on the engine, but it didn't really help. I then took the cylinder head off the machine and ran a 0.200" diameter drill up from the bottom side of the valve cages, about 0.6" to cut down on the amount of friction between the valve stems and the valve guide portion of the valve cage. I took the heavy springs and cups off and put the originals back on. I reground the valves. Nothing really helped get my compression back.  Something I have noticed over the years--When the seat portion of the valve cage gets too large, it is almost impossible to get a good valve seal. I'm stumped at the moment. I may machine new valve cages and reface the valves in the lathe, more or less starting over again with the valve sealing issue. I have rechecked the valve and ignition timing, but they are fine.

Offline Roger B

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Re: T head engine by Brian
« Reply #175 on: September 16, 2021, 07:01:17 AM »
Are you sure it is actually the valve seat that is leaking and not the joint between the cage and the cylinder head? There is quite a short path to the port.
Best regards

Roger

Offline Brian Rupnow

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Re: T head engine by Brian
« Reply #176 on: September 16, 2021, 03:34:51 PM »
I spent all of yesterday flogging a dead horse. Today I am going to make new valve cages and loctite them into the head. A close visual inspection of the existing valve cages shows that the seat area has become too large because of repetitive lapping to get a good seal on the valves. Also, due too the method I used when making them, the seat area is not perfectly centered on the guide area. I tried to take picture to post here, but my digital camera can't get a shot which shows it clearly.

Offline Brian Rupnow

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Re: T head engine by Brian
« Reply #177 on: September 16, 2021, 09:39:47 PM »
So, here is a family picture. The cylinder head with new valve cages pressed and loctited in place, the old valve cages which have been pressed out (You can see the excessively large valve seat area in the picture), along with valves, keepers, and springs. I haven't used my special tool for cutting new valve seats into the cages yet, I'll wait until the Loctite dries 24 hours. I am now using my wifes old digital camera, as it takes pictures much more clearly than mine. Design review came back to my customer today on the welding fixtures I designed, and it looks like I will have a full day tomorrow just making all the changes.

Offline Brian Rupnow

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Re: T head engine by Brian
« Reply #178 on: September 21, 2021, 12:29:06 AM »
It's been a wild and crazy two weeks since I first had this engine running. I have been very busy changing my shop around to make room for a big DoAll Bandsaw and preparing to sell my smaller metal cutting bandsaw. Strangest thing---the engine ran fine before I painted the flywheels and gas tank, but after the paintjob I couldn't get this thing to run for love nor money. These engines are not terribly powerful, and I was having enough interferance between the large timing gears and the aluminum casings over them to keep the engine from running on it's own. The engine ran again on it's own for the second time about 3:00 this afternoon, and I've been chasing down interferences and tight spots until about 20 minutes ago. The small carburetors from Traxxas are just right for these engines I build, but the throttle is very loose so that it can be operated by a servo. I don't use servos to control my engines, and the default setting is for the carburetor to open the throttle wide open just from engine vibration if I don't have something connected to that throttle. Tomorrow I will post a better video out in my main garage where there is lots of natural light with the garage doors open, and I have a better hook up for the engine throttle.---And yes, that little 10 blade fan being ran from the flywheel by a rubber o-ring puts out an amazing amount of air over the cylinder.---Brian

Offline Art K

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Re: T head engine by Brian
« Reply #179 on: September 21, 2021, 02:43:04 AM »
Brian,
It is good to see that you have sorted out the problems and have the T head running again.
Art
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