Search results

Thanks Dale. Making the crankshaft next. Reason - it is easier to ream the bore of the crankcase nose to size, rather than machine the shaft. There are various ways of doing the crankpin onto the shaft, I used to prefer a pressed in pin, but more recently I have changed to machining it on...

Here is the cylinder with the slots cut in. Used a 40 mm diameter 2 mm thick slitting saw and went in 7 mm. I have a slotting arbor but it is too bulky for this type of work so made up a simple saw holder as shown and it works a treat. But you could achieve the same result almost using a...

Well here's another hours and a half's work, yet to be lapped. But I have to admit I spent about another 90 minutes playing with some 10/20 then 10/40 material that I was never going to be happy with the finish. Eventually found my 12L14 in a big enough size - then stuffed up the first attempt...

I built this from Ron's site plans about 2 years ago. It runs superbly, often starting first flick. Not the easiest of engines for a newcomer to builds as it requires quite a bit of thread cutting. And make sure you use a good heat treated alloy for the muff, those very thin fins are easy to...

Here's the maybe finished crankcase - maybe because not sure now if I will radius the outside edges above the nose and rear cover - was going to but don't mind the look of it with the square edges. total time so far 5.5 hours, with 4.5 hours spent this morning carving up this piece. Have...

Here is the start of the making of the crankcase. Had some beautiful heat treated 42mm diameter aluminium, it machines like a hot knife through butter. Machined off a piece just over the 41.25mm length then milled it 28mm square. So we have made a start - now to do the lawns before dinner...

Terrific news, Aussie Steve has been working with me converting the rudimentary drawings onto CAD. He is now up to date with all I have done so far and I can tell you it is very impressive. Steve has his own way of doing things, which is a bit different than past CAD drawings I have used and...

Here is the piston and the conrod drawings. The notes on them are pretty explanatory. Note the piston/rod assembly is probably a bit heavier than normal, so there will be some metal removed from the crankdisc to help counter-balance this. I think making these components just a bit heavier and...

We are now in the final phase of the design. A myriad of notes are on the drawing, I am using a 5.5mm hole at the bottom of the venturi with a 5.5mm hole in the shaft with a timing of 50 degrees BTDC on the upstroke of rotation. This gives around 135 degrees of inlet opening which then gives a...

Have now put the crankcase parameters into the drawing and initial thoughts on crankshaft design within the crankcase. Note the inlet transfer ports have been slimmed down to 6mm from 8mm. I think 8mm would slow the gas speed too much. Have also shown the exhaust ring with either a slitting...

OK next phase of the design is to decide on a few crankcase details. 1. gudgeon pin height - free to choose, if a bit lower down the piston than half way means the conrod can be a bit beafier and still have freedom of movement, so lets say 7.5mm from the top which is 5.5mm from the bottom. 2...

Here is the next installment - about 2 hours work laying out the cylinder. This aspect was done using the parameters developed from the initial sketch above. Note that the exhaust port has been narrowed from 3mm to 2mm. The various lengths have been decided now and incorporated into the drawing...

I haven't been too active here for a while, as I have been busy with finishing off a 1964 Lotus Seven which is so much fun to drive, along with building a 160% Tomboy powered by a modified Owen Mate for the recent Oily Hands weekend at the Cowra Model Aero Club in honour of David who I miss very...

Without a mill you do have some difficulties Maybe an approach you might consider is to bore the big end and little ends to size in a piece of suitable diameter rod with some overhang each end, then machine the central part of the rod using the chuck one end and a live/dead centre the other...

Neils, one day I will get around to making a backplate that allows a lot more volume in the crankcase and see what happens on a back to back test, I too am curious. I gave up on the throttle, no consistency, so made a normal venturi inlet with a PAW NVA. This then ran to 10300 with my test 9x4...

I was given these by a mate - and they have been incredibly useful for my model engine making. There were quite a few in the tin and I don't think I will need anymore - they range from those that can bore a hole just bigger than an 1/8th of an inch to internal threading down to around 1/4 inch...

Hadn't thought about that - but it would make a super powerful engine that's for sure. Might have to make a triple size Tomboy to use all that power !

Here's the finished engine. First time I've used a throttle and it idles quite well, but quits when opened more then about 60% - suspect the venturi size it a bit big and airflow slows at full throttle and suction decreases even though I've tried it richer. Here's a short video of it...

Blimey, that's amazing. I believed my mate but never thought wood pistons would be used as much as they obviously were in hard times to keep things going. And I bet I am in the majority in this lack of knowledge !

Anyone come across a wood piston in a working engine ? A good mate of mine when doing his apprenticeship swears the college had an engine given to them and they ran it before stripping it, and it ran ok. When they stripped it they found a piston made of hardwood ! He thinks it was an A model...