|Steve G||01/01/2019 20:56:45|
19 forum posts
I have machined, completed an IC twin Inline Engine that might be of interest to those something doing similar.
I have run the engine but not too impressed with the glow plug ignition system, I think spark ignition would be better.
Engine running here https://youtu.be/JS3N3v8eq5I
Edited By Steve G on 01/01/2019 21:01:52
Edited By JasonB on 02/01/2019 07:05:49
|Ian Skeldon 2||01/01/2019 21:26:15|
|337 forum posts|
That's lovely mate, nice one.
|251 forum posts|
|Great, makes it all worthwhile!|
3292 forum posts
A beautiful piece of work. Lovely to behold.
|1023 forum posts|
That's a very nice engine, impressive.
14874 forum posts
|John Penfold||02/01/2019 08:07:50|
|20 forum posts|
97 forum posts
Very impressive work - thanks for sharing!
|Niels Abildgaard||02/01/2019 18:45:55|
|191 forum posts|
Can you describe how crankshaft is made?
I have tried to make normal ,pressed up two stroke cranks and failed miserably.
More than once
|Mogens Kilde||02/01/2019 18:54:29|
|58 forum posts|
Absolutely great piece of work
Thank you for sharing this
|Neil Wyatt||02/01/2019 20:01:52|
15587 forum posts
Great stuff, must be satisfying to achieve that range of speed control on your first run.
14874 forum posts
Looks like a schillings style crank shaft to me.
|Craig Booth 1||02/01/2019 21:15:55|
|39 forum posts|
That's beautiful Steve, lovely work.
I have the plans for both that one and the 4 cylinder boxer which is next on my list.
Is yours going in a plane?
Would love to know more about it if you don't mind?
Did you stick to the materials, specifically the piston liner and ring combo? I was planning on changing to steel liner and CI ring.
What do you think the issue with the glow is? I was also thinking of changing it to petrol, but was nervous about losing power. Mines destined for a plane if successful.
|Jeff Dayman||02/01/2019 22:29:29|
|1407 forum posts|
That's a fine engine Steve, runs really well! Great job.
|John Olsen||03/01/2019 06:03:39|
|937 forum posts|
It's quite often a bit tricky to get multicylinder engines to idle nicely on glow, the plug naturally cools down at slower speeds, and if you use a hotter plug to compensate it may be too hot at high speeds. One solution is a glow driver. These can turn the glow plugs on at low power settings, usually by connecting to the servo wiring. Of course for ground testing one doesn't always have a servo connected, but you can always just have a switch and turn on the glow plug at lower speeds.
Craig, I have messed around a bit with spark ignition on a commercial engine (Saito) and I don't think there is any loss in power worth worrying about. Perhaps just a little since it is usual to drop the compression ratio a little to run on petrol. The biggest problem is getting the mixture right if you also use petrol instead of methanol, but they will run fine on spark with methanol and give a lovely slow idle. You do have the weight of the extra battery for flying, you don't want to use the ignition battery for the RC gear!
|Craig Booth 1||03/01/2019 12:26:48|
|39 forum posts|
John, not wanting to hijack Steves thread, but what compression ratio do you think would be required to convert to spark ignition?
|Richard brown 1||03/01/2019 12:33:44|
|61 forum posts|
|Steve G||03/01/2019 14:24:45|
19 forum posts
I am stunned at the interest for this engine and very humbled by it - I work alone from time to time in my garage and no-one here, at home that is, seems in the slightest interest!
I will try and answer some questions;
Niels; The crankshaft is made up in sections as illustrated and a press fit of the crankpins (with some bearing loctite) was used. The mail problem was, on first assembly, is ending up with a lot of run-out (a banana). The remedy is to try and maintain concentricity during the removal and replacement of the same component during machining operations. It took a while getting that right and I fear is the main downfall of many of these types of engine cranks. I used 12L14 for the main crank parts with two ground silver steel rods for the crank pins.
Craig: Contact me any time, glad to support you - I have cheated in some areas and more than happy to share. I am also building the 4 cylinder boxer engine and happy to report that the crank is turning with no binding (with some tweaking) - no small feat with built up cranks. I used the same cast iron Meehanite for both liners and rings, seems to work fine. I see no reason for using steel liners, they should work fine and be less messy around the lathe although take longer to hone. I put a You tube video out on my 'Heath Robertson' cam grinder, it is a real hotch potch but works which is the main thing. Finally the heads require some thought working out what the drawings say.
John: The engine has a lot of compression, and is difficult to start due to this, but I believe that spark ignition is the way to go. I think I left too much material in the head, for fear of drilling through too much, leaving long glow plug holes - thereby leaving the business end of the glow plug a bit far up the hole. I think spark plugs would work better as this is a large engine - and finding 1.2 volts at 5 Amps is a pain, read 10 Amps for the 4 cylinder!
My cam grinder, for those interested is here - https://youtu.be/jQpSARubxKY
Edited By Steve G on 03/01/2019 14:25:19
|John Olsen||04/01/2019 04:20:04|
|937 forum posts|
Steve, you might find it easier to start if you splash out for an electric starter unit. Saves a bit of wear and tear on the hands too. You do have to make sure you don't flood the engine and then force it over with the starter, that will bend things.
I can't remember how thick the shim is under the Saito cylinder, maybe 15 or 20 thou or so. There was some info in RCM&E a few years back, not sure if I can find those issues now. The cdi unit I used is the RCEXL unit. They are available from places like Hobby King or on Ebay. (No connection, just a satisfied user.) There is a twin cylinder unit, but I think that is meant for twins that fire 360 degrees apart, eg a waste spark will occur on the exhaust stroke. I don't know if Steves engine above is 180 or 260 degrees. If it is 180 you would want two single cylinder cdi units and two sensors. You can also get an optically isolated switch to let the RC side of things turn the ignition off, a handy feature.
Or you could try the Minimag people...I don't think they have any kits in stock currently but I am hoping they will put one together for me shortly, and maybe if a few other people show interest they would make some more.
|Mick B1||04/01/2019 09:22:04|
|918 forum posts|
Outstanding piece of work.
I'm familiar with 4-stroke parallel twins from motorbikes a long time ago, and this has a similar configuration, but what about ongoing lubrication? The parallel twins I remember had oil pumps, internal oilways to crank- and camshafts, dry sump systems and separate tanks.
Please login to post a reply.
Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!
You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.
Click THIS LINK for full contact details.
For subscription issues please see THIS LINK.