Completed Twin Inline IC Engine

[Steve GParticipant @steveg24616]

[Steve GParticipant @steveg24616]

Hi All,

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

Steve

 

Edited By Steve G on 01/01/2019 21:01:52

Edited By JasonB on 02/01/2019 07:05:49

[Ian Skeldon 2Participant @ianskeldon2]

That's lovely mate, nice one.

[AJWParticipant @ajw]

Great, makes it all worthwhile!

Alan

[HopperParticipant @hopper]

A beautiful piece of work. Lovely to behold.

[Thor 🇳🇴Participant @thor]

That's a very nice engine, impressive.

Thor

[JasonBModerator @jasonb]

Very nice.

[John PenfoldParticipant @johnpenfold74932]

Fab.

John

[LADmachiningParticipant @ladmachining]

Very impressive work – thanks for sharing!

Anthony

[Niels AbildgaardParticipant @nielsabildgaard33719]

Lovely engine

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 KildeParticipant @mogenskilde92996]

Hi Steve

Absolutely great piece of work

Thank you for sharing this

/Mogens

[Neil WyattModerator @neilwyatt]

Great stuff, must be satisfying to achieve that range of speed control on your first run.

Neil

[JasonBModerator @jasonb]

Looks like a schillings style crank shaft to me.

[Craig Booth 1Participant @craigbooth1]

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.

Thanks

Craig

[Jeff DaymanParticipant @jeffdayman43397]

That's a fine engine Steve, runs really well! Great job.

[John OlsenParticipant @johnolsen79199]

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!

John

[Craig Booth 1Participant @craigbooth1]

John, not wanting to hijack Steves thread, but what compression ratio do you think would be required to convert to spark ignition?

Craig

[BufferParticipant @buffer]

Steve
That is lovely. What other engines are on the shelf then?

Rich

[Steve GParticipant @steveg24616]

Hi All,

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

Steve.

 

Edited By Steve G on 03/01/2019 14:25:19

[John OlsenParticipant @johnolsen79199]

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.

John

[Mick B1Participant @mickb1]

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.

[Steve GParticipant @steveg24616]

Hi Mick,

That' a great question. I have assumed that with only one compression ring, the lubricating oil in the fuel would pass the ring on the cylinder wall and disseminate in the crank case. This would then form a fine mist that would 'wet' all of the roller type bearings in the engine. Note that there are no plain bush type bearings, On the rear of the engine is a breather that emits black oil deposits so that may be indicative of lubrication occurring.

To confirm how well this is accomplishing adequate lubrication I will have to disassemble the engine but I ask those here on the forum whether my theory above is correct or they have a better explanation than I do.

Steve

[not done it yetParticipant @notdoneityet]

It’s a 180 degree crank, not the usual 360 parallel twin as fitted to many British m/cycles. It may need to have a higher idling speed because of the unequal firing interval but does away with some of the crank out-of-balance issues of a 360 crank.

More like the Honda 250 and 305 Dreams of the early 1960s and the CB450 Black Bomber later in the decade. The magneto on one of my stationary engines (a V-4) is driven at crankshaft speed, but only revs to about 2200rpm, not over three times faster! The Honda engines simply had two sets of contact breaker points, IIRC – iI’ve not looked at my CB450 for probably ten years.

Regarding lubrication, compression rings are, primarily, just that. Bottom lubed petrol engines utilise oil scraper rings to prevent oil going up the bore, with multiple compression rings to prevent fuel finding its way downstairs, so a necessary added complication.

The two (or typically three) rings in motorcycle (and car) engines may well reduce blow-by to a minimum (I have one engine with about six piston rings, mind – never had it apart and cannot get to the Blackstone manual at present). But I know little re these tiny engines – one and two litre cylinder displacement are more my type of engine!

[Mick B1Participant @mickb1]

I'm obviously talking way above my level here – I never twigged the petroil lube or 180 crankshaft, which presumably are referenced in the drawings or backing literature, or maybe just expected background knowledge. I'm sure I've seen ball and roller mains and bigends in 2- and 4-stroke m/c engines that weren't force-lubricated, so I'd imagine your theory will *probably* work. But of course, in the 2-stroke case, unburnt petroil passes through the crankcase and over the components inside, whereas what's getting there in your engine – if I've understood correctly – is burnt combustion blowby. Will there be any effective oil left in that?

[Tim StevensParticipant @timstevens64731]

Mick B1 says: I'm sure I've seen ball and roller mains and bigends in 2- and 4-stroke m/c engines that weren't force-lubricated

Indeed I'm sure you have. The major reason for using roller mains and bid ends is often to avoid the need for an oil pump etc. Especially on two-stroke engines – those which do have oil pumps tend to feed the oil into the inlet stream, and don't have pressure feed (which is difficult in any real sense with a rolling bearing).

Up to the 1930s, many (four-stroke) cars had no pressure feed to the big ends, they relied on a dipper in a trough of oil. The last time I looked, some mowers still did …

Cheers, Tim

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