4 stroke single

[Roger B]

Thank you both    This engine was intended as a learning/training exercise and I am slowly reaching my goal. I want to really understand how things work and what affects what (it's part of my day job as well  ). The way it runs now is approaching what I hoped for when I started sketching it out (on the back of an airticket) but I still want to understand why it would not initially run with the CDI but now seems to run best with it    Other than the heat insulator playing with the cams and the carbs does not seem to have had much effect.

[Roger B]

As the sun was shining I opened up the R&D department to make some measurements.

Using the Rcexel ignition and the commercial carb as before it would run between ~2000 and 8000 rpm. It didn't seem very sensitive to the mixture needle or timing. I then connected the load bank and a got a best result of 11.5V at 1.8A = 20.7W at around 6000 rpm. As with my horizontal engine the cooling was insufficient under load so I need to consider a water pump and a fan.

I may also make a crankshaft mount for the hall sensor so that the ignition is sensing at the correct speed and the advance is not doubled 

[Roger B]

I spent some time tidying up this engine. The coil and amplifier ignition was removed and the CDI was fixed in place. I made some fixing holes for a cooling fan (the one fitted is the shell of the one I burnt out on my horizontal engine and then tried to see if I could dismantle it and fix it). I shortened the universal shaft driving the generator by 20mm so the terminals didn't hang over the edge and made a proper spacer to get the generator at the correct level. I need to buy another fan and also fit a voltage regulator to protect it so as not to repeat my previous experiment.

[Roger B]

I decided to make a crankshaft sensor mount for the ignition to see how it responded compared to a camshaft sensor. It is a brass  top hat bush soldered onto the timing gear cover and an aluminium carrier for the sensor that can be rotated to adjust the timing.

Unfortunately I misread my drawing and turned the top hat bush to 22mm instead of 20mm and then bored the first carrier oversize  I was able to salvage the bush by making an 18mm mandrel that I could mount in a 10mm MT2 collet and then clamp the timing cover to the face plate.

[Roger B]

The Hall sensor mount was then rounded on the RT and slitted for the clamp screw. The recess for the Hall sensor cover was initially drilled with two 2mm holes and one 5.5mm hole and was then cleaned up with a 3mm end mill.

[Admiral_dk]

Nice holder and I especially like your attention to protect the wires - looks good and should last forever 

[Roger B]

Thank you Per    The protection for the sensor and wires came with the sensor from Just Engines so I decided to use them. They are designed to mount by the prop driver of a model aircraft engine so I guess they have to be quite robust 

[Roger B]

I drilled a 2mm hole right through the starting freewheel housing and then opened one side up to 3.9mm for the magnet. The idea of the through hole was to allow the magnet to be removed if necessary. I also added an M2 grub screw above the sensor to stop any chance of it vibrating out.

The first trial runs did not show a significant difference between the crankshaft and camshaft sensors but I was having problems with the engine suddenly stopping during load testing but it would immediately restart without changing any settings. This happened with both sensors and both carbs  The only obvious change I can think of is some different, larger bore fuel tubing. I think there was a discussion on here some when in the past (possibly in one of Brian R's threads) regarding petrol attacking certain materials 

<a href="https://www.youtube.com/watch?v=eVDhSmm1AXI" target="_blank">http://www.youtube.com/watch?v=eVDhSmm1AXI</a>

[Brian Rupnow]

Roger--You're right. I did post about fuel attacking the tubing used as fuel line. On one of my engines, the fuel didn't flow very freely---in fact it had turned to a semi jelly. I don't remember now, but I think it was generic hardware store clear vinyl tubing. I changed to a fuel line made specifically for gas fueled model airplane engines, from my local hobby shop, and haven't had any more problems.---Brian

[philjoe5]

Nice runner Roger.   I'm catching up on some of the posts here and hadn't looked in for a while. 

I hope you sort out the problems soon.  They don't seem formidable.

Cheers,
Phil

[Admiral_dk]

Fuel lines for gasoline, methanol and dielsel (CI) engines are three different materials and you need to use the right kind.

[Roger B]

As we had some nice weather outside I had another play with this one. I put the old fuel pipe back on and then tried some load testing. It runs better with the commercial carb than the one I made (which I think is too small).
It will start and idle quite well although I do need to make a throttle lever. The light bulbs are around 10W load and then I tried with my load bank. I could drive around 10.5V into a 6R8 resistor so around 16W, nothing like strictly businesses outputs but I'm happy 

I think that is the end of trials with this engine as I am planning a revised version with the same external dimensions but double the capacity.

<a href="https://www.youtube.com/watch?v=9FOV1FHP8ww" target="_blank">http://www.youtube.com/watch?v=9FOV1FHP8ww</a>

<a href="https://www.youtube.com/watch?v=TxuoA5YyDZI" target="_blank">http://www.youtube.com/watch?v=TxuoA5YyDZI</a>