Thompson Engine

[michael-au]

Cup washer and cerclip made for both valves



Test fit for the valves and rocker arm



as can be seen here, the measurement on something is not quite right between the rocker are and valve

It looks like the dimension for the rocker post is a quarter of an inch to long
I cut 1/4” off the post and it looks much better

 

[michael-au]

Pull start pieces are finished, not much had to be done just a clean up of the casting

 

[michael-au]

Started on the fuel mixer its not really a carry as it has no butterfly of barre, just a needle valve



made the bolt the holds the mixer to the head, this bolt is hollow and has a hole drilled in the side so the fuel can pass through it



Taped a scrap piece of aluminium to hold the bolt while drilling the hole in the side of it





made a start on the needle valve

 

[michael-au]

All parts of the air fuel mixer are complete

 

[michael-au]

Piston almost finished just have to put a grove in the gudgeon pin hole for a circlip on either side

 

[michael-au]

Out smarted my self with the crank, I decided to make it one piece instead of 3, I now know that was not a good plan
Starting to assemble the engine, go to the point of test fitting the piston and conrod, well there is now way to get the rod onto the crank ( bugga )
I ended up machining the pin off and making a bush to fit the rod and bolt it on like the plan said all good now

Just have to make rings and sort some sort of ignition

 

[michael-au]

Decided to make a finned exhaust

 

[michael-au]

managed to get grooves for the circlips machined in to the piston, I made a mandrel to hold the piston, was just a push fit as the machining ws very light and shallow, works well
Made the circlips out of piano wire
Two rings all most completed

 

[michael-au]

Rings done and installed


Piston and rod installed, just have to workout the ignition points

 

[raveney]

Rings done and installed

View attachment 147601
Piston and rod installed, just have to workout the ignition points

View attachment 147602

Hello Michael,
Very nice work on this. I really like the aesthetics/style of the engine frame and cylinder and may take a crack at it for a future project. Could yo please explain what the casting is that covers the crankshaft and connecting rod? Oil bath...splash guard..? Is it open below? A few pictures would be great if not too much hassle
thank you,
Russ

 

[michael-au]

Hello Michael,
Very nice work on this. I really like the aesthetics/style of the engine frame and cylinder and may take a crack at it for a future project. Could yo please explain what the casting is that covers the crankshaft and connecting rod? Oil bath...splash guard..? Is it open below? A few pictures would be great if not too much hassle
thank you,
Russ

Hi Russ
The casting is just a cover over the end of the crank, its not open on the bottom

 

[michael-au]

Got the points and ignition system sorted out, engine is now complete

 

[michael-au]

Time to see if it will fire and run, I put fuel in the tank, no Leakes that's good

Set the timing roughly, probably to roughly, it fired and then back fired and the result was the liner was pulled down and jammed on the crankshaft

It seemed like a tight fit, I had to heat the casting in the oven and the liner in the freezer to get them together

I did have some concerns about how the plans said to fit the liner as there is no lip on the top to stop it from being pulled down
I should have made a new liner from the start, lucky no real damage was done, I have striped the engine down and recessed the top of the cylinder casting and will make a new liner


(bugga)


Machined the recess in the top

 

[michael-au]

New Cylinder liner made and loctited in

 

[michael-au]

Managed to get the engine reassembled today

I did manage to get it to run but it does need a bit more fine tuning