30cc Flat Four (Puma)

[doubletop]

Good news!

The relacement ignition unit arrived today. Sky-Fly Hobby Store, on AliExpress, were good to their word and replaced the single unit they'd sent in error with the twin I'd ordered. They didn't require me to return the single unit as it would have cost them more than their wholesale price.

Hobbying are still out of stock of their Phoenix clones of the RCexl units, I guess there may be a bit of a story behind that, so if you are looking for a supplier you could try these guys

https://www.aliexpress.com/store/group/Ignition/2622044_512156680.html

So next step is get the timing set up and see if I can get it to run.

Pete

[doubletop]

Well we have a runner!!

It was pretty painless, if you take operator error out of the equation.

The first issue was quickly apparent. Air was being forced into the fuel tank rather than fuel being drawn from it. I’d set one of the camshafts on the wrong face of the lobe so the timing was out. It was sorted without a major disassembly. With the magnet disk removed and the grub-screw on the sprocket loosened the shaft can be adjusted. I used a small drill chuck to grip the end of the camshaft.

Next was the setting of the timing of the magnet disks. The RCexl tacho (the thing that falls off the bench about 1 min into the video) triggers as the magnet comes near the Hall sensor. I was using that as my indication of the trigger point. There is no indication in the RCexel documentation what edge is used by the unit. I was also concerned when the spark seemed to be intermittent. I now know that the unit requires both edges of the pulse from the Hall sensor to be seen before it will spark. The stable state is a high level, it goes low on the leading edge of the magnet and then high again on the trailing edge. That’s when the spark is generated. These edges need to be in relative quick succession, which may be a reason why these units don’t work that well for slow speed engines.

The carburettor I’m using is an ASP clone of the OS engines carb for their OS180FSR engine. I found the OS and ASP setup manuals and used the instructions to preset the carb. This video is directly after me doing that initial setup.

[youtube1]https://youtu.be/WM5IEEMxxNc[/youtube1]

All in all I’m pretty pleased with the result at this point. As Jason reported with his flat twin, a bit of oil is being burnt by cylinders 1 and 3 as oil is lifted by the rotating crank. At the moment I don’t have any baffles.

That’s it for this weekend, we have a beautiful weekend here in Wellington so neighbours are out enjoying the spring sunshine so any more runs can wait for a weekday.

Pete

[Jasonb]

That's running well for the first attempts, oil is not too excessive just hope you don't have an oily residue down the side of your car!

[Jo]

  Well done Pete

Jo

[bruedney]

Nice one Pete

[doubletop]

Jason, Jo, Bruce

Thanks.

Fortunately, any oil didn't get as far as the car, as I had only washed it this morning. I do have an oil leak out of the crankcase but haven't discovered yet where that came from.

I've tweaked the cam settings a bit, my eyeballing of the exhaust valve opening wasn't as accurate as it could have been so I've re-done it with the DTI. I've also discovered why it shut down when I closed the throttle. The slow running stop wasn't set so the barrel closed off completely.

It looks like tomorrow will be another fine day. That said, it isn't as loud as I expected so may just give a brief run and get some close-up video, particularly of the timing belt in operation.

Pete

[Roger B]

Excellent for the first run     

[doubletop]

Thanks Roger

I'm as surprised as anybody how well it went for a first try. The Bobcat and Lynx took weeks to get to run and even then they weren't that good. I'm learning a lot from this project, particularly what to expect. I'm already thinking that the Bobcat and Lynx will need to be dusted off and given another chance.

Pete

[Jasonb]

So Whats Next?

Malcom did not get far but you could do the NE30-I4 or NE45-V6, it's really just the crankcases that change and he also went with Schillings style built up crankshafts..

[doubletop]

Jason

The thought of making six of everything doesn't appeal that much. We did discuss whether this project should be a V4 or flat 4 and went for the flat 4.  Although it does cross my mind that, if I donated the parts from the Bobcat and Puma, I already have six of everything. With range of crankcases, cranks and camshafts the builder could assemble whatever took their fancy. A bit like Lego. Singles, Twins, 4 or 6 cylinder, inline, flat or V or even radial. RCexl do an ignition for 3, 5 or 7-cylinder radials.

BTW - I do like the way Malcolm reduced the spacing of the cylinders on the inline 6 I could have done that with the Puma, saved a bit of length on the crankshaft and reduced the 6mm shoulders on the journals.

Pete

[Jasonb]

I think a one piece head would also go well with the straight 4

[Brian Rupnow]

Congratulations. A very pretty little engine and definitely a runner.---Brian

[Dave Otto]

Nice work, congrats on the first pops!

Dave

[doubletop]

Jason

A one piece head could look good but would move away from the concept of a modular design for many configurations

Brian

I'm pleased and it certainly appears to demonstrate the benefit of O rings vs CI rings which I picked up from one of your videos. In my case I've made the piston grooves to take CI rings but used 2 x 1mm section Viton O rings instead.

Dave

Thanks for your support

Pete

[Art K]

Pete,
Sounds great for a first run, congratulations. DTI Is how I set the timing on my VAL. The indicators don't lie.
Art