Thompson Engine

[michael-au]

I recently started to build a Thompson Single Cylinder Engine

The first operation was to machine the base flat





Next was to machine the bottom and the top of the cylinder flat and then bore out the casting for the steel liner



Taping the holes out that fix cylinder to the base

 

[michael-au]

Next operation was boring out the casting for the steel liner



Line up on the centre mark using a laser pointer


First drilled a pilot hole, starting with a small drill and ending with a half inch drill



Then on to the boring head to bore out to final size

 

[michael-au]

Mounting face for the conrod cover was milled flat



After matching the flat two holes drilled and countersunk mounting to the base

 

[michael-au]

Drilling and reaming holes for the main bearings
I machined two locating plugs so I could line up the centre of the cylinder, to make sure the crank and camshaft were straight inline with the cylinder

 

[lee webster]

I don't know this engine, I am fairly new to model engineering, but that looks great! I love watching build threads, a chance to learn.

 

[michael-au]

Turning the crankshaft
The crank for this engine was meant to be made in 3 pieces, but I decided to make it in one piece

first I turned the front end down to size, then I had no way to hold it in my 4 jaw chuck, the jaws couldn't close down far enough to hold it with the offset I had to have
So I then made a fixture to hold it in the 3 jaw chuck, using a piece of round aluminium I drill and reamed a hole to fit the shaft, I then cut a slot along the hole
The hole and the seat came out to be almost the same size, I pushed a small screwdriver into the slot and that allowed the shaft to slide in, taking the screwdriver out and it locked on to the shaft
This allowed me to turn the rest in the 3 jaw chuck, pressure from the chuck jaws also held the shaft solid

 

[Steamchick]

Hi Michael, LOVE IT!
But just as an observer, and not really knowing how stiff the farme is, (it looks quite "flexible" for machining?) I would have put a support beneath the cylinder while you were skimming the top and drilling the bore? (first pic #2):

Anyhow, it looks like you managed a good job.
Wll done on an excellent and enjoyable log!
K2

 

[michael-au]

Drilling and reaming the rod was next
I made a fixture to hold the rod so I could machine both sides flat and to size then drill and ream them

 

[michael-au]

Hi Michael, LOVE IT!
But just as an observer, and not really knowing how stiff the farme is, (it looks quite "flexible" for machining?) I would have put a support beneath the cylinder while you were skimming the top and drilling the bore? (first pic #2):
View attachment 146163

Anyhow, it looks like you managed a good job.
Wll done on an excellent and enjoyable log!
K2

Hi K2

Thank you

Your probably right but it was very rigid though and only very light cuts

Michael

 

[GreenTwin]

Good machining and photography.

Getting good photography in a shop setting is very difficult for me, as is good machining sometimes.

.

 

[michael-au]

Cutting the slot for the woodruff key in the crankshaft

 

[michael-au]

scrap one plug :-(

\

put that down as a practice one

 

[michael-au]

Pushrod for the exhaust valve, this engine doesn't have a pushrod for the inlet valve

 

[michael-au]

Cleaning up and broaching the slot in the flywheel

Mandrel was used to machine the second side of the flywheel

 

[michael-au]

Machine a grove in the bottom end of the fuel tank to take an Oring

Also turning the inside of the top of the fuel tank and drilling the holes

 

[michael-au]

turned a short piece of aluminium to fit inside top and bottom of the fuel tank so the two holes would line up when drilled
The holes in the bottom plate were taped and brass dome nuts for the top

 

[michael-au]

Turned the dome on small cnc lathe and hex was on the cnc mill using the 4th axis

 

[michael-au]

Mounting for the fuel tank was milled flat and then drilled and tapped

 

[Steamchick]

You are making this faster than I can read your posts!
Well done!
K2

 

[G54AUST]

Hey Michael.

Following your current build closely. (And the Demon build) What's the origin of the casting kit/plans ???

Is that a HM50/51 mill your playing with ??? I've got the HM52 H/V with plans to retrofit for CNC.

Regards,

Trevor,
Melbourne, AU.