Twin cylinder open crank marine engine

kuhncw · Mar 27, 2016

Hi Dougie,

Your engine is looking great. I especially like your exhaust manifold and stack.

How will you control engine speed? I'm guessing the plate and lever on your carb is the choke.

I'm certainly looking forward to hearing it run.

Chuck

fourstroke · Mar 28, 2016

Thanks Chuck

I'm hoping to use the shutter on the carb to set the speed, I dont know how well this will work but I hope it wont take much fiddling between needle valve and shutter to get it running at a steady beat
I'm aiming for a slow speed set up, if you have any advice then let me know

Regards

Dougie

kuhncw · Mar 28, 2016

Hi Dougie,

Your carb setup is like the mixers I use on hit & miss engines where rpm is controlled by the governor latch out. I can't say your design won't work, but I'd think it would be very touchy to adjust in order to hold rpm and keep the mixture correct.

I think you'd need a throttle of some sort, maybe like the barrel throttles used in simple model airplane carbs. George Britnell has designed and built throttling carbs for his multi cylinder engines. Perhaps George will chime in on this.

Chuck

fourstroke · Apr 5, 2016

A little more progress

I needed to come up with a system of getting oil to the big ends, I had left very little room between the nuts holding the bearings together and the vertical part of the con rod
The solution I came up with after a lot of thought is shown in the first few pics. Its a length of 5/32" brass tube reduced to 1/16". I drilled a hole 1/16" dia as close to the base of the rod as possible, through the steel part and a little way into the top half of the bearing. This hole was then drilled at an angle through to the bearing surface using a 0.6mm drill

The oiler will be held to the conrod with a 1/32" rivet through the tang filed at the top, I will fix it with loctite on final assembly

The last couple of pics show the main bearings with their oil cups fitted

Not very exciting but every little bit helps

Regards

Dougie