How about a 180 (30cc) glow motor?

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I don't think the piston weight would be the only factor in limiting the revs. There has to be more to it than that. what about the balance of the crankshaft to the piston / rod assembly?

Ian, what squish and C.R were you running with the A100? Did you try other combinations on it?

I think 23,000 would be the target rpm range also. More usable (especially in a mono) than 19000.

CNC prop's then casting from Cobalt chrome? It would want to be right first time out!!!! that could get pretty darn expensive....
 
Craig,

If you are talking about an A100 with a P&L made to 30mm bore you have a 18.4cc motor instaed of a 17.2cc. Might start to run into problems with flowing enough through the inlet and exhaust to support that capacity. Also Mr Phelan's liners would be awfully thin for AAC if you go to 30 bore..... : :)

Maybe we should talk to Brad Christy about a long rod for the A100 then add liner shims to suit. Or have an AAC P&L done to suit.

Nitrocrazed racing: I took a lot of fuel on Sunday and came home with very little....
 
Tim,

Maybe there is something in the balance, but rod length might be more of a culprit.

I ran 11 thou clearance and 17:1 compression, same as the A-90HP and K-90. I did not experiment with ratios. Although I am thinking about doing another head with all taper on the squish band after reading what John Ackermann said about that today.

The CNC machining would be very cheap (this is a good friend!) The cobalt chrome stage costs about $60 I think. It would be a bit of trial an error, but starting with the best props I can find and modifying them to suit my application.... Could get very interesting.... 8)

Ian.
 
Speaking of Mr Phelan, he was at the regatta centre on Sunday.

As for the ports not flowing enough - I doubt that would be a big problem.

The longer rod / sleeve shim/ head button is an easy option but not so cheap for the Ti rod. Sleeve shims ain't a problem.

I'd forget about going oversized in the bore on the A100 until we can get the thing to rev. Solve that issue then go for it!

I'm loving this thread ;D
 
Tim,

The longer rod may get tricky. The top of the exhaust port in the sleeve of the A100 already is very close to the top of the port in the case. If you made the rod 2mm longer the top of the port in the case would need to be ground out about 2mm, and I dont think the casting is that thick there! It may need a special piston with the pin closer to the top surface.

Head button is as easy as a bit of CAD work and buying a carton of beer. ;D The liner shims are hard for me, but I have done it before.

Brad Christy is the only person I have heard of who could do an appropriate rod. Do you know of someone making custom steel rods? ???

Ian
 
Folks,

Going back to the RPM thing.... the THREE factors against the 100 are:

Rod length, Piston weight (maybe negligable but its there) and bore/stroke ratio.

Now with a heap of grunt to spare (and possibly sacrifice) what would happen if we got a 100 case and piston/liner and put a 90 crank in it?? massively oversquare engine.. More RPM.. less torque...question is are we taking too much torque chasing the RPM??? We can always lighten the 100 piston at the same time.. :)

EMS Racing The Dremel is your friend
 
Ian,

now you catch on to the idea of an A97!!! will need a new head button and cooling jacket at the very least with the head button going another 1mm down the bore (assuming we dont need to move the piston/liner)..

would like an extra 1mm in the rod though....

The A100 is close to a 105 anyways...

Craig ... oops EMS Racing
 
Ian,

I am concerned that there will not be a recess for the piston which will come 1mm closer to the crank on the down stroke.

Also if you have the 3 piece head/cooling combo (old style) then the cooling isnt a problem... but if you have the 2 piece I couldnt be bothered making the heads like that. Thats where the plug cooled heads come in handy. Makes the head buttons so basic to make. means you can spend more time making more head buttons
 
Now with a heap of grunt to spare (and possibly sacrifice) what would happen if we got a 100 case and piston/liner and put a 90 crank in it?? massively oversquare engine.. More RPM.. less torque...question is are we taking too much torque chasing the RPM??? We can always lighten the 100 piston at the same time.. :)
Click to expand...
Hmmmm,

Personally I don't think we can utilise all the torque anyway on the big motor's due to prop' sizes and bad handling characteristics. I'd say it's worth a shot. If we are changing the crank it should be balanced to the piston / rod anyway so the dremel would be required!!!!

As for the piston / crank clearance on the down stroke - is there enough metal there to skirt the piston without messing up the port overlap?
 
Whoa guys! Think about it! With a shorter stroke the piston stays further away from the crank with the same rod length...... ;D

A new one piece head is not a problem.... Takes about a week. 8)

How about the A100 crank in the A-90HP? Gives 16cc, a bore of 28mm and a stroke of 26mm. Would require a new head button (or 39 thou of head shims!), and the piston fit would be a little tight for a while. May not require that much tweaking of the ports to get the timings the same! Uses the A-90 lighter piston.... ;D

Nitrocrazed racing: Too much stroking.....
 
Craig,

A-90HP:

Bore: 28mm

Stroke: 24mm

Rod length: 45mm

A100

Bore: 29mm

Stroke: 26mm

Rod length: 45mm

K-90

Bore: 27mm

Stroke: 26mm

Rod length: 45mm

Well how about that.... ;D

I guess that dispells the theory about the A100 having a poor stroke/rod length ratio. It has the same ratio as the K-90, which revs quite nicely thank you! :-

The plot thickens.....

Nitrocrazed racing: There's no substitute for CUBES!!!!!
 
Hello ,

I am new to the forum and this is my first post. This topic is something that has intrigued me for some time. I have told the Browns that if they ever decided to build something like a MAC 1.2 to be sure to put me on the list for one. I know how the MAC 84 runs in my 80 size boat, I can only imagine what something like a 1.2 or 1.3 would be like.

Hey Andy, get the plans drawn up and get it into production. There's people who want them.

Virgil Ericksen :D
 
Hey Virgil,

welcome aboard.

Ian, Id be happy with anything bigger than 25cc but 30cc would be cool. Why not go to the legal limit - building it will still cost about the same ;)

stroke / rod length on the K90 is the same as the A100? There must be something else limiting the RPM then. Has anyone else run an A100 with a tacho? Maybe it's just Ian's motor that won't rev.

What about an intlwaters.com designed engine? Any manufacturers want to take it on 8)
 
Ian,

The 2mm bore difference is probably a large factor and the size of the crank assembly, the K90 has a small crank compared to the A90/100

Dale
 
Tim,

Mine also doesnt rev. Maybe I should attack it with Mr Dremel to SC Specifications? Also I have a Muck 90 pipe which may do the trick. We may just be choking the 100 engines down with 90 pipes (pipe stinger may be too small???)

Dale,

What happened to you over the weekend??? I got 2nd in Group 27 and 5th in Opens... Gotta get a different chassis for the Hornsby track for my open car...

Ian,

Oh you havent posted since I last posted in here.... :p

EMS Racing bigger better more fasterer
 
Craig,

Yep I want it ALL!!! ;D

Tim,

Exactly, the rules say 30cc, so make a 30cc engine!

The Bore/stroke ratios are not the same, but the stroke/rod lengths are the same. Hard to imagine the 2mm larger bore wipes off 3000 rpm!

I doubt you will find anyone else who has run one with a tacho! When I bought my tacho Dave Males said he had sold one to Roger Brookes, but that was the only other one in Aus!

I can provide design input! 8)

Ian
 

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