How about a 180 (30cc) glow motor?

[Ian Inverarity]

Dirty cheater! :

Ian.

 

[Ian Inverarity]

Hmmm,

This thread got less response than I thought it would. I am trying to get some idea of the interest there would be in a 30cc motor of basically the configuration used for 15cc motors currently. If anyone is interested, please post! 8)

Ian.

 

[Ian Inverarity]

>>I would like to see a drum valve - a really big one supported by bearings, a 1 piece crank that won't run - out like the CMB's, but with a good crankpin so that it doesn't shear off like a Picco. I'd also like to see a titanium rod with needles top and bottom, a billet piston with large pin bosses and a large gudgeon with teflon retainers.

Lots of head retaining screws - say 12, and a head with plug body cooling passages close to the plug threads. The bore and stroke ratio would be interesting, Having a large capacity the bore size and the relationship of the plug to combustion chamber size would be tricky. I do not like multi -plug heads but it might be needed for a motor of that size.

Tim,

Hmm, not bad, but I prefer disc to drum! A four bearing crank like an A-90 cant run out. The problem with titanium rods is they need a hard steel sleeve for the needles to run on, which could get bulky at the top end of the rod. An A-90 has a stepped gudgeon pin, so only needs on teflon pad. Did you see the cooling on my K-90 head button? ;D

Ian.

 

[TimD]

>>The problem with titanium rods is they need a hard steel sleeve for the needles to run on, which could get bulky at the top end of the rod. An A-90 has a stepped gudgeon pin, so only needs on teflon pad. Did you see the cooling on my K-90 head button? ;D

Ian.

So are you saying the ti rod with a hard sleeve in it would be a dissadvantage over a steel rod? mmmm...... what am I overlooking?

I've seen single pad gudgeons before - good idea - one less part to worry about.

I didn't see the head on your K90 mono - whats the story?

What do you think is the cause of the A100's 19,000 rpm limitation? something to look into on a larger motor perhaps?

 

[Ian Inverarity]

Tim,

The disadvantage is the ends of the rods would be larger to achieve the required strength because of the extra thickness required for the sleeve. I dont think I could use one of Brad Christy's rods in the A motors because of the clearance needed. Not really a big deal for a new design I guess, but also there is the cost issue to consider.

The K-90 head had a groove in it which went quite close to the plug and the combustion chamber surface. You really need to see a drawing of it to appreciate what I am talking about.

19000rpm rev limit. Very good question. The rod and bottom end of the A100 is the same as an A-90HP, but the stroke is longer. This would change the stroke to rod length ratio, but I have no idea of the effect of changing that. I can only speculate that maybe there is a pipe problem that limited revs even when I shortened it dramatically. I doubt the 29mm bore causes problems with incomplete combustion, it is only 1mm bigger than the A-90 uses. I honestly dont know.... :-

Ian.

 

[Ozzy]

Ian

To build a 30cc glow engine that will rev the bore to stroke will need to be over squar i found this out after speaing to a frend that was involved with the motorcycle racing and they liked engines with big pistons and short stroke.

CHD Racing Paul

 

[Ian Inverarity]

Paul,

The A100 is still over-square. 29mm bore by 26mm stroke. The A-90HP's are 28 x 24 (very similar to the CMB 90's) but the K-90 is 27 x 26 and seems to rev harder than A-90 but make less torque. Your MAC's (with the exception of the 84's) are closer to square than the K-90 and they rev pretty well!

I still have no ides what was limiting the revs on the A100, if I figured it out I would still be using the motor in the mono.

Ian.

 

[TimD]

Ian,

Rod length / stroke ratio is interesting. A whileback I witnessed a O.S 46vrm fitted with a vx piston and liner and other mods. That thing was a rocket. One thing we thought that contributed to it was the rod length / stroke factor...

I THINK ??? a longer rod with the ports further away from the crank while maintaining the same stroke would mean less load on the wristpin and less sideloading on the piston. Does that make any sense at all?

Tim.

 

[Ian Inverarity]

Tim,

I really dont know. I have heard mentioned something about reducing the angle that the rod makes, thus reducing the side thrusts on the piston etc and making more direct force on the crankpin. ie the longer the rod the less angle the rod would go through.

The rod length is also a factor in the whole time/area question, but I have no idea of what the effects are.

Ian.

 

[EatMyShortsRacing]

Hey Ian,

Have you checked to see whether the rod length is the same for the 90 and 100? Thats the 3rd part of the equation... Then you have the 4th and 5th elements etc... LOL

I only have assembled engines and not all that much time on my hands at present to check this but if my logic follows, since they are the same case casting (100 is a taller case) and the exhaust port is around the 180 degree mark that would mean both liners would match the exhaust port in the case and the rod length would be identical. Here I am answering my own questions....

Now comes the big question.... what is the relationship of all these items... bore/stroke/rod length

The other thing stopping the 100 from revving out harder is the extra piston weight over the 90 but that also comes into the above equation because the rate of acceleration/deceleration of the piston is going to relate to that formula...

Have I lost everyone yet??? I sort of know where I am heading with this..

EMS Racing E=MC2... that makes me 2MC2S Racing

 

[TimD]

since they are the same case casting (100 is a taller case) and the exhaust port is around the 180 degree mark that would mean both liners would match the exhaust port in the case and the rod length would be identical.

Graig, you lost me there.....

Maybe we should look into getting some figures from known "revvy" engines for bore / stroke / rod length / piston weight . What do you think guys?

 

[Ian Inverarity]

Craig,

Yes I did check, the rod is exactly the same in the 90 and the 100. The 100 case is taller, but the exhaust port is higher on the on the sleeve and actually matches the case better than the 90's. Remmember the A100 has a 2mm longer stroke, so this would be why the port is higher with the same rod length. Also there is much more liner above TDC on the A100, so the head button is deeper to match. I have absolutely no idea why.

The bore/stroke ratio is more square on the 100 and the stroke/rod length is higher. What this actually does (or why it does it) is completely beyond me.... ???

The 100 piston would not be a great deal heavier, it is only 1mm bigger in diameter. I dont have scales good enough to measure them tho...

You have lost me.... ;D

Nitrocrazed racing: If H-50's are too small for my 90, what the heck am I going to use with the 100???

 

[Ian Inverarity]

Tim,

I have the bore, stroke and rod lengths for A-90HP's (revvy), K-90's (revvy) and A100 (NOT revvy). Piston weights I dont have. My pistons weigh less anyway..... ;D

Ian.

 

[TimD]

Ian,

Better take the prop off the rescue boat!!!!!!

The reason I was so interested in the rpm limitation is because it relates to prop selection - whats the use of having a low revving - high torque motor if there are no prop's to suit it. ( except for gear drive but to multiply prop speed rather than reduction.)

 

[EatMyShortsRacing]

Ian,

I think it might be an idea to weigh the pistons to get a feel of how much the 1mm adds to the piston weight... and acceleration being exponential in nature I would also assume the addition of a small amount of weight will be magnified in its effect???

Ian, can you send me those b/s/r comparisons?

EMS Racing

 

[Ian Inverarity]

Tim,

Haha, actually I have a friend who uses a CNC mill, who can also help with computer modelling of props. Then I can model what I want, cut an aluminium prototype and have a Cobalt Chrome prop cast by another guy over here. Long term project at this stage, but with interesting potential..... ;D

I am interested in the rev limitation too, the A100 would be much more useful to me if I caould get it to run about 22-23000 rpm. Actually on the subject of the 30cc motors, this is a definate advantage of the 2 cylinder engines, they should rev as hard as a 90.

Gear ups have a lot of friction losses....

Ian.

 

[Ian Inverarity]

Craig,

You may be right about piston weight, but consider some of the new mod 4 port zenoahs are getting to 18000 rpm with a MUCH heavier piston and rod.

I will post the b/s/r ratios tonight, I dont have the rod length info with me.

Ian.

 

[EatMyShortsRacing]

Ian....

Cant you tell... I have a plan!!!! ;D

 

[Ian Inverarity]

Craig,

Now you have lost me completely.... ???

Ian.

 

[EatMyShortsRacing]

Ian,

let me look at a couple of things tonight... with a lil machining here and there..... I am guessing there could be an A97.... although my calculations see the bore/stroke ratio as correct in the 90 but not the 100. There is part of your rev limiter. The rod should also be a little longer to get the 100 to rev out. I am thinking that the reason for the higher case in the 100 is the manufacturer may already know this and made the case so it could support a longer rod (with a lil help from Mr Dremel).

with a 26mm stroke the piston should be around 30mm... maybe we can see our local AAC piston liner man for a prototype???? LOL

EMS Racing the brain took a licking but it kept on ticking