How about a 180 (30cc) glow motor?

[RIGGERMORTISE]

Ian

I thought you may be able to build it with me, it should take about two years with all the other projects we have on the go. ;D

 

[Ian Inverarity]

Rigger,

You mean a Dyno? I have given it a little bit more thought actually, there is a practically dissused dyno room at work that might come in handy...... ;D

Ian.

 

[Ian Inverarity]

David,

The magazine was Model Boats, Feb 2000, and the name of the boats owner was Lionel Lawley (I think?)

Ian.

 

[EatMyShortsRacing]

Ian,

I still think Multi Cylinder is the way to go. Think about it... a 45 is less than twice the horsepower of a 21. A 90 is less than twice the horsepower of a 45.. 2 90s invariably will have more horsepower than a single 180...

For my money the best plan would be to gear 2 90s together, but with the exhaust leaving the engine like a Pylon engine.. main shaft overdriven for more rpm at the prop. Thats where the horsepower really would be!!!

EMS racing 200th post!!!! Yippee!!!!!

 

[Ian Inverarity]

Craig,

Cost in the penatly of multicylinders. Actually I am not sure that 90's have less power than 2 45's. I think the 90's and 21's are the best of the engine sizes at the moment.

I think a twin cylinder 90 would have more potental power and revs than a single 90 BUT will be heavier, larger and more expensive. Then there is multiple pipes etc. Tuning two carbs at once.

I'm betting a 30cc single will be more viable! ;D

Nitrocrazed racing. 525th post...

 

[EatMyShortsRacing]

Ian,

Just a thought... why is F1 going to v10s and v12s??? I dont believe any 90 is twice the horsepower of a good 45. In my book the costs are not outweighted by the benefits... and hell, 2 geared into one or a current day twin... which one will be heavier?? also only one drive shaft...

EMS Racing

 

[Ian Inverarity]

Craig,

All F1 engines are V10's. Years ago after the turbo era there was V8's, V10's and V12's. Then Renault became particularly dominant with a V10. The V8's were lightest, but least powerful, the V12 were largest and heaviest but most powerful. V10 was the in between and a better compromise. Because of Renaults success even Ferrari stopped making V12's and went to V10's. A few years ago they changed the rules to make only V10's legal.

Their engines represent cubic dollars tho. Each cylinder is 300cc, last years BMW engine revved to 19000 rpm. This is equal to the average peak revs of my 17.2cc A100!!!!

Built right a 2 cylinder 180 should be more compact and weigh less than 2 geared 90's. Gears is entirely another problem. But the approach of building a 2 cylinder 180 in a common block with the cylinders next to each other and gearing the cranks is one I mentioned earlier, it would be an engine similar to a Rotax 256. But with both cylinders vertical. Two pipes out the back, two carbs at the front. My preference would be to have the output shaft at crank speed from one side, but it could have an integrated step-up gear train for a shaft in the middle. Higher revs equate to higher friction losses... But the high revs/low torque could make it useful for monos. If the revs are high enough standard 90 size props could be used. I doubt that many will take the load however....

Such an engine should be lighter than two geared seperate 90's, and also much narrower. It would probably fit in a 6" tub like an original Eagle. Considering the number of standard parts, particularly P&L's, cranks, discs or drums etc, it would be a relatively easy project to prototype.

Biggest problem I see for such an engine is gears. To take the sort of power we are talking about with any decent life, these will not be off-the-shelf gears. They will be expensive.

Hmmm, I'm getting interested in such a beast. Anyone else? Maybe I need to do some drawings....

Nitrocrazed racing: Shirley you can't be serious...

 

[David Singleton]

Ian

Lional Lawley has built a tethered hydro fitted with 3 OPS 10cc engines that were connected with toothed belts however the belts self distructed within seconds of the engines being started.

Lional has said he will be fitting a gear train to connect the engines but I have not seen him lately so I do not know how he is progressing with the project.

Our tethered season starts in April so as soon as I hear anything I will let you know how the hydro performs and knowing Lional he will make it work if he can.

Dave

 

[Ian Inverarity]

David,

Do you know anything about the single cylinder engine I saw in the magazine?

I had always thought that belt drives would not work for engine interconnection! Gears would be the way to go, but you would need good gears.

Ian.

 

[David Singleton]

Ian

The engine in the hydro you saw was a home built 30cc glow by Lional and held the record at one point.

I will try to contact Lional and see if he will give me the specs for the engine.

Dave

 

[Ian Inverarity]

David,

That would be quite interesting! 8)

Ian.

 

[Ian Inverarity]

Tim, Craig, Dale, Mark et al.....

I stripped both my A-90HP and A100 today in the interests of seeing what is possible with part substitution as was covered earlier in this thread.

As near as I can tell the cranks will interchange between the motors. However to put the long stroke crank in the 90 would require the clearance groove in the case to be machined deeper to clear the rod. Also a 1mm head shim would be needed. Effect on timing unknown....

The 90 crank goes in the 100, but this would require a new head made 1mm deeper (or modify current head). Effect on timing unknown.

Any new ideas of which option is worth persuing (or none at all)? Both options would give a cubic capacity between the 90 and 100. One gives a large bore/short stroke and the other option gives medium bore/medium stroke. My favoured theory is that the engine needs to be larger to use the higher capacity so neither option would confirm that, although my preference would be to long stroke the 90. If the longer stroke didn't rev as hard as the 90 it would confirm that the engine is too small.

Ian.

 

[Mark]

Just a bit more about f1 engines,

The V8 has the torque but little in high rpm power, the V10 has a happy medium of rpm and torque, the V12 has the high rpm power but absolutely no torque in the lower range which makes it hard to drive when you're not in the zone. All these configurations are made using the same capacity, power is calculated from power strokes of a piston so the more cylinders you have producing more strokes the more bhp you get at the shaft which is why they design the engines to rev so hard, more strokes per minute means more power somewhere but you have to be able to use the power if it revs hard but in a very small rev range it is not much use, you can even raise the rev range so high to get more power that the engine can't drag itself up to the zone

 

[Ian Inverarity]

I have started laying out the design for a 2 cylinder side by side engine with geared cranks. According to calculations based on fan similarity laws, to absorb twice the power from the same prop, the speed would have to be increased 1.26 times, thus from about 22000 rpm to 27700 rpm at the prop. Screaming!

I started to layout the engine with a crank like the Vok 15cc pictured earlier, but basing the design on A-90's this is not actually really feasible as the drum internal diameter could only be 13mm, which is a bit small on a 15cc cylinder. You only find this stuff out when you start drawing it!

With a cylinder spacing of 45mm, the overall width of the engine (including the mounting rails) would be about 112mm, so the engine would go into 5" rails.

With only 45mm between the cylinders, this is why I am looking at drums rather than discs. The A-90HP discs are 48.5mm in diameter. Because of the problem I mentioned above about drum diameter I am looking at making the rear crank into a drum type system as used in CMB hydro motors, but supported in bearings.

Nitrocrazed racing: It all sounds easy until you actually start drawing it.... :

 

[Ian Inverarity]

Okay Ladies (judging by all those avatars) and Gentlemen:

The fruits of my labour: A 2 cylinder 30cc engine with geared cranks and a step-up drive.

The first pic is a section thru one of the cylinders. The design is based upon A-90HP cylinders, rods and exhaust headers. The carbs are A-90 as well, but slightly modified. The engine is about 190mm long from carb to flywheel and is 90mm wide with no engine rails. The length comes about partially from the gearbox at the rear, but also the long drum system used at the front.

The cranks are each supported in 4 bearings. The front cranks are also the drum valves, and supporting them in bearings and the size and geaometry of the drums means that the engine is fairly long at the front end.

The rear cranks have the gears located on a taper, held by a nut. The end bearing of rear crank is in a cover that goes on the rear, this also locates the bearing for the output shaft. The gear ratio is a 1.25 step up. The centre output shaft is integral with it's gear and is supported by bearings, with the larger bearing at the rear taking any thrust loads if a flex hex is used.

The cylinders seperate from the case for ease of manufacture, and as well as the heads and cooling jackets are seperate parts

The carbs would be connected with a link such that they operate together.

This is only a rough layout sketch to verify the feasibility of the layout. Much more work would be needed to turn it into a useful design. Any comments/ observations/ suggestions/ critiscisms? ???

I apologise for only 2D drawings, but as yet I am not as skilled as Wade in 3D modelling. If there is a favourable reaction to the design I might consider it a good project for me to teach myself 3D parametric modelling....

Nitrocrazed racing: Imagine the sound.... ;D

 

[Ian Inverarity]

Here is the top view of the engine. This is a much more confusing drawing as I didn't worry about hidden lines etc and everything is just drawn on top of each other. Basically a layout drawing.

Nitrocrazed racing: Past 600....

 

[TimD]

Looking good Ian,

Any thoughts on the issues I raised with you regarding hydraulic's if one motor goes out?

Tim.

 

[EatMyShortsRacing]

Ian,

I gather the rotation of the actual engines is backwards? As an example, using old 21s in gear drives meant the exhaust faced the back of the boat because the geared shaft is rotating the opposite way.

I was planning on trying this with the old CMB 80 GP engines whuch you could reverse the crankcases on (would also work on Rossi 90s) but never got around to it..

Craig

 

[Ian Inverarity]

Tim,

As I said earlier I dont think that would be an issue. I also doubt the engine would run for very long after one cylinder went out anyway as the load on the other cylinder would be very high and the boat would probably come off plane.

How do you feel about a 180 2 cylinder putting out 12hp at 27500 rpm as opposed to a single scyinder 30cc motor putting out 12hp at 20000 rpm?

Ian.

 

[TimD]

Ian,

You are probably correct in that the other cylinder will stall due to the load but my concern is that it one cyl. gets water injested into it the rotation of the other cyl. will force it to hydraulic pretty quickly.

I have to admit I think the twin Cyl. motor will be a lot easier to get happening as we can use existing parts. I doubt the power figure though especially if you are gearing up the output. It would still be plenty of power though..... A H50 at 27500rpm would be pretty fast! Did you work out the exact gear ratio's yet? I think if we had say 8 -10 HP and bulk rpms we will still pull the really big prop's.....