In-line triple 45cc

[johnlaudano]

I'm working on a self-designed in-line triple. it uses a few parts from airplane engines but most are my design. the cylinder heads, sleeves, cams, and pistons are from Magnum 91's. The rest I've designed. it's water/air cooled and will have glow ignition. the intent is that it would power a large model boat similar to others in my prior posts. the water cooled system would be a recirculating system this time as the pump is centrifugal and not self-priming; a raw water system needs to have a gear pump to be reliable and consistent. my plan is that the exhaust pipes will not be water-cooled this time; just short stacks.
Thus far I've made no effort to balance the crankshaft/ connecting rod/ piston assembly. anybody have thoughts on this? will the rocking effect, fore-to-aft, be excessive at this scale at perhaps 2500 rpm? could adding weight to the flywheel and timing gear end of the crankshaft suffice?
john

 

[kuhncw]

John,

It is nice to see another one of your engine projects. Nice work. I would like to see more detail on your crankshaft design.

I can't comment on the rocking effect, but adding weight (inertia) to the flywheel is always a good idea to help the engine at low rpm.

Please keep us up to date on your progress.

Chuck

 

[johnlaudano]

Chuck,
the crank is made in pieces with the shafts pressed into the discs with 1/8 pins and loctite holding them. there are four ball bearings; one on each end of the crank (one is in the photo) there will be two others, one each on the center discs (only one is installed in the photo).
The small brass slugs between the center discs are counterweights for the center portion of the crank; the center conn rod shaft is longer than the other two and has two brass spacers that need to be compensated for.
I realize that using four ball bearings is an expensive way to go about it and in fact it may be that only one center bearing is needed to prevent the crank from deflecting. I also considered that, at this scale, center bearings of any sort may not be needed.
The reason that the conn rod shaft lengths are not the same is due to design compromises related to accommodating the center to center spacing of the cylinders related to my use of model airplane engine heads. the cylinders are uniformly spaced apart.

 

[kuhncw]

John,

Thanks for the crankshaft design details.

I see your crankcase has endplates. I suspect the front and rear crank bearings mount in the end plates? How are the second and third crank bearings mounted within the crankcase?

Chuck

 

[natalefr]

Good job

 

[johnlaudano]

John,

Thanks for the crankshaft design details.

I see your crankcase has endplates. I suspect the front and rear crank bearings mount in the end plates? How are the second and third crank bearings mounted within the crankcase?

Chuck
You are correct. End bearings are in the end plates. The center bearings fit in bores inside the crankcase and will be held in place with loctite 680.
John

Good job

Good job

Good job

 

[johnlaudano]

Chuck
You are correct. End bearings are in the end plates. The center bearings fit in bores inside the crankcase and will be held in place with loctite 680.
John

 

[kuhncw]

John,

Is your crankcase open at the bottom, then closed with a plate or is it one piece bored through for the main bearings and opened out if needed for crank and rod clearance. It looks like your camshaft housing is a separate piece and bolted to the block. You always come up with unique designs. A few more photos would be great. I'm just trying to understand your crankcase design.

Thanks.

Chuck

 

[johnlaudano]

Chuck,
yes the bottom is open and will have a simple cover plate. the photos attached all show the bottom. in the other photos you'll see the bearing bores; they are slightly smaller than the rest of the bore in the crankcase.
As in most things in life there are endless compromises. Home engine design too. The cam housing is separate and is screwed to the main crankcase for ease of machining. both crankcase parts started as round stock. There are oil passage holes between the two for splash lubrication of the cam. My next design is going to have an oil pump that will direct oil onto the cam.

 

[kuhncw]

John,

Thanks for the photos. That is an interesting design. I like it.

Chuck

 

[johnlaudano]

here are a few more current photos. its almost complete.

 

[Johno1958]

I like your engine. Very interesting.
Cheers
John

 

[natalefr]

Congratulations !

 

[kuhncw]

John,

I like the design concept and the style of your 3 cylinder. Very nicely done.

Is the radiator from a computer cooling system? What is the black coating on the inlet and exhaust piping?

I'm looking forward to some video when you run it.

Chuck

 

[johnlaudano]

Chuck,
Yes the radiator is from the computer world (and China); I added the neck and cap. No pressure relief valve though.
Next I need a gas tank and to do the electrics for the glow ignition.
The starter motor is a bust. I burned out the second one today.
Video in a couple weeks hopefully.
John

 

[johnlaudano]

Chuck the coating on the pipes is auto shop high tempcronkle finish rattle can paint.

 

[propclock]

Nice , only 1 comment, I put a fairly big flywheel on a 4cycle
O.S.Max powered Dumas Cris-Craft . Once when I made a fast turn at high speed it did a 360 degree barrel roll in the air! No damage,
but flywheels do have centrifugal force/energy. Nice low idol
but I was totally shocked when it happened. I just used a water
pick up tube after of the prop, typical to power boat racers.
Interested in many years of RC boat modeler magazine?
Just pay the shipping, hate to throw them away.

 

[bluejets]

As #17 says, no need to run complex water recirculation systems in a boat.
The head cooling as it stands will be more than sufficient for the run time between start-up and placing in the water so the simple "true and tried" pick-up from the prop is more than sufficient.
If you plan to run it on the bench or at displays then ok.
In the past I've used K&S 3/16" thin wall brass tube as a pickup taking care to face the tube forward and directly at the "upsweeping propeller blade tip".
Tubing will take a small amount of heated bending without requiring any sand packing. Connection back to the cooling distributor via silicon tubing.

Flywheel, yes, as big and as heavy as design will allow.
With 45cc capacity, the boat will be rather large and not be a drop in the ocean so-to-speak as far as any weight concern.
Reason is, these 4 strokes can get REALLY snappy and cantankerous without it. Remember with an os61 fs in a chopper I built back in the '80's. A real PIA.

Starter will need a lot more gear reduction as it's just WAYYYY too much loading as is. These motors like to rev and if your starter speed is down it will simply cook the guts out of it.

Friend of mine is currently building a 3 cylinder 150cc 4 stroke for a scale loco and I built the CDI ignition system and the starter system controls. Used a brushless motor in this instance but the principle of gear reduction applies just the same.
He is using a crank with 1,3,2 firing with all exhaust strokes to follow so will be a rather different sound I think.

Nice work by the way.

PS...just saw the needle valve position....could be tricky to get at.
It is possible to add an extension but care needed in the design as vibration will simply snap them off.
Methanol fuel needs to be flushed out of the engine at the end of the day, especially if you are using any nitro content. Remnants will convert to acid and rust the crank and any other steel component like crazy, seen it with the 25cc 4 cylinder boat engine I built here.

 

[johnlaudano]

this is the completed engine. thanks for all the comments. i'll send a video of the first run if its a success (or if its a spectacle of a failure).
also, before anyone asks, the reason there are four slots in the flywheel when only two are needed is that there was a drafting error.

 

[johnlaudano]

Today I ran the triple for the first time. more video soon.
John