Author Topic: Thompson Engine From Scratch  (Read 5763 times)

Offline flopearedmule

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Re: Thompson Engine From Scratch
« Reply #15 on: December 15, 2020, 11:40:50 PM »
That looks nice Jason
I really enjoy your pictures and how you silver solder everything together.  You have the talent and patience that I need/ or wish I had.

Offline Bear

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Re: Thompson Engine From Scratch
« Reply #16 on: December 16, 2020, 03:31:39 PM »
Excellent! I like your YouTube videos as well.

Offline mnay

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Re: Thompson Engine From Scratch
« Reply #17 on: December 16, 2020, 07:26:05 PM »
Thanks for spending the time to show us your methods and process.
It looks great.
Mike

Offline Jasonb

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Re: Thompson Engine From Scratch
« Reply #18 on: December 21, 2020, 07:31:38 PM »
Thanks for the interest Guys.

Just a small post tonight. I was not that keen on the fuel tank or carb shown on the earlier engines so I decided to go for something similar to what I made for the Midget not least because I still had five of those miniature jam jars to find a use for!



Apart from having it screw into the cylinder head rather than use a flange mounting the only other real deviation was to have a lever to rotate the throttle barrel rather than using the actual jam jar. The CNC made quick work of this with a 3mm 3-flute cutter blending all the internal and external radii perfectly, I set the CAM to leave a couple of tabs so the part did not fly off part way through cutting and these were easily cay and removed with a needle file.



<a href="https://www.youtube.com/watch?v=GwlnREMKA0s" target="_blank">http://www.youtube.com/watch?v=GwlnREMKA0s</a>

I used a piece of 8mm copper brake line for the exhaust which was filled with lead to stop it collapsing while being bent over a former. The lead melted out without sticking to the uncleaned copper so it was easy to silver solder on a short length of brass drilled 6mm and threaded M8 x 1.0mm so it could be screwed into the head and like the carb locked with a round nut with two spanner flats as I felt that looked a bit nicer than the usual hex nuts.



That just about completes the construction. I have test run the engine but did not bother to video it, these tests did show that it gets quite hot so my hopes to paint it in Kawasaki green have had to be put on hold as I felt some VHT paint may stand a better chance of surviving and their "kermit" green is not as bright :(. Now that the paint has had time to harden I'm waiting for a bright day to take some photos before the paintwork gets mucked up with oil etc doing the video run but hope to have pics and a video for you soon.


Offline mnay

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Re: Thompson Engine From Scratch
« Reply #19 on: December 21, 2020, 07:38:58 PM »
We will look forward to the video!!!
Mike

Offline Jasonb

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Re: Thompson Engine From Scratch
« Reply #20 on: January 18, 2021, 01:11:24 PM »
Well I finally got round to taking some photos of the finished engine, apart from the colour which was darker than I intended I'm happy with the way it turned out.










Offline Bear

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Re: Thompson Engine From Scratch
« Reply #21 on: January 18, 2021, 03:24:22 PM »
Great work.

Offline Dave Otto

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Re: Thompson Engine From Scratch
« Reply #22 on: January 18, 2021, 03:58:47 PM »
Very nice!

Dave

Offline Admiral_dk

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Re: Thompson Engine From Scratch
« Reply #23 on: January 18, 2021, 08:51:09 PM »
Elegant result  :ThumbsUp:

Offline scc

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Re: Thompson Engine From Scratch
« Reply #24 on: January 18, 2021, 09:45:49 PM »
A lovely engine Jason.     Silver soldering fabrications looks a better alternative to my welding......I need to get a new torch. Apart from all the programming, etc  the cnc makes light work of fancy shapes.  Thanks for your educational posting.           Terry

Offline AlexS

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Re: Thompson Engine From Scratch
« Reply #25 on: January 20, 2021, 07:50:51 PM »
wow very nice! green paint fitted very well!

Offline Brian Rupnow

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Re: Thompson Engine From Scratch
« Reply #26 on: January 20, 2021, 09:45:47 PM »
Jason--that is a lovely engine.-I really like it.---Brian

Offline gbritnell

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Re: Thompson Engine From Scratch
« Reply #27 on: January 21, 2021, 12:09:18 PM »
Well done Jason! Quite a unique engine.
Talent unshared is talent wasted.

Offline b.lindsey

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Re: Thompson Engine From Scratch
« Reply #28 on: January 21, 2021, 02:30:03 PM »
Very nice Jason. I like the color too!!

Bill

Offline Jasonb

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Re: Thompson Engine From Scratch
« Reply #29 on: January 21, 2021, 04:32:56 PM »
Thanks for all the appreciative comments, even from those who like the shade of green. It's growing on me a bit but having always pictured this one being painted with Kawasaki green in my mind while designing and building the VHT Kermit Green was a bit of a let down  :disappointed: There is always this option if I still don't like it.



But onward to the important bit before anyone thinks I may not have fully finished the engine before moving on to the Heinrici. Unlike a few engines this one seemed to run better after stripping and painting and starts first time after a pull of the cord which I can get 5-6 winds around the starter pully. It's still running quite hot particularly when I lean it out which also ups the revs and makes the throttle a bit more responsive. Richening the mixture a bit slows it down to a more pleasing (to me) speed but then the throttle has little effect.

I did not play with the timing on the video as it is hard to do up the adjuster one handed and did not want to risk things coming loose as during initial testing that did happen and the brass ignition contact went through the open gears and was spat out the other side in several pieces :'(

The exposed gears and crank make it a bit noisy but it does make for a more interesting engine when running rather than having everything hidden away inside a crankcase and the dirty oil seems to wipe off Ok ;)

<a href="https://www.youtube.com/watch?v=JJZusJ63Huk" target="_blank">http://www.youtube.com/watch?v=JJZusJ63Huk</a>

 

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