DPittman
Ultra Member
Not yet.. 95% done. Maybe by the time Peter gets another 3 radial engines made and an airframe to put them on I'll get mine done.Is that ultralight of yours actually airworthy
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Radial engine build
- Thread starter PeterT
- Start date
I haven't been posting much, but I have been progressing at my usual glacial speed. I found these glow plug ignitor modules out of China. I think they are voltage regulators but have some desirable features. they can accept elevated voltage input, say from a 2 or 3S lipo battery at 8 or 12v respecively, but delive the requisite 1.5-2.0 volts to the plug. Each plug can draw 2-5A depending on some variables which makes them a bad match for any kind of standard cell for all 5 cylinders, especially old school NiMH cells. Anyways I ganged them in parallel, made some copper bus bars & basically have a dedicated switch for each plug. Turn them on to start, turn them off when running/glowing. I can test combinations like lower cylinders only at idle. I tested on a mockup & the plugs all lit, so magic smoke escaped. I also found these nice harness plugs which engage the glow plug stem. They have a contact spring inside.
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I made a model scale version of a leak down tester like auto engine techs use. Basically you have high pressure feeding a gage from a compressor regulator, then an orifice restriction in between the second engine reading gauge, then a hose to a shop made plug fitting. Pressure was set about 40 psi initially. I initially used a sensitive needle valve rather than what would be a teeny small orifice hole, somewhat guessing at diameter. The procedure is: put piston at TDC, open the inlet valve to source pressure, open needle valve slightly & observe. Ideally both gages should read the same number with no hissing coming past either intake or exhaust valves, or blow-by past ring into crankcase.
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Did I mention the initial TDC thing? Yeah if its not there the prop kicks when it sees pressure causing much bench commotion LOL. I didn't have enough hands to hold the prop in position & snap the trophy pic with both gages gages reading very close to equal pressure for as long as I want to stare at it (ie. success!). I have no valve loss & just very slow leak off past the ring gap. Everything is new so should get better yet when broke in. For sanity check I pulled one of my dads old engines which I knew was running & got identical results (again, a dummy picture before pressure up & TDC). So on to the text task.
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Dan Dubeau
Ultra Member
What a fantastic thread, and beautiful engine. Thanks for sharing.
Former Member
Guest
Nice!!!
Thanks guys. Regarding test run... 'soon' LOL. I'm slowly running out of things to deal with machining/construction wise, so its more about careful top end assembly, rechecking timing & rocker gaps, all that stuff. I need to make some custom gaskets for certain surfaces I'm pretty sure will leak nice things get warm & shaky. I'm quite certain I'll be into the engine many more times yet, thinking otherwise is probably wishful thinking. What I'd like to do is run it my back yard close to my shop where the tools are. But I don't think my neighbors would appreciate my hobby & I don't really have anything secure to mount it to yet. My flying field has a clapped out picnic table that could use some castor refinishing, but the entry is still snowed in & it would be a long drive knowing I'd forget or require something.
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Where abouts is your flying field?
No, tried dabbling with single channel ages ago (about the time galloping ghost was the rage) and that was a total disaster. Mostly free flight and control line. My son has gotten into RC and has been 3D printing aircraft. He is/was a member here https://www.amasrc.ca/ ?
It runs! I need to figure out a way to link a video.
Doing an inspection teardown down. Things look pretty good, but a few tweaks here & there. I decided to make some head shims to adjust CR a bit. These are 0.005" thick & rather fussy things to make. Ideally I would like some even thinner. Perhaps there is an easier way than these fixtures but clamping & alignment& tolerance is rather important so kind of what I came up with. Just in case you find yourself having to make something similar. Step-1 ID bore
Doing an inspection teardown down. Things look pretty good, but a few tweaks here & there. I decided to make some head shims to adjust CR a bit. These are 0.005" thick & rather fussy things to make. Ideally I would like some even thinner. Perhaps there is an easier way than these fixtures but clamping & alignment& tolerance is rather important so kind of what I came up with. Just in case you find yourself having to make something similar. Step-1 ID bore
