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Engine basics => Engine set up tips => Topic started by: Chris McMillin on October 18, 2018, 07:07:28 PM
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I'm building two Berkeley Minnows for a B Team Race demo and am using McCoy 29 RR redheads. I'm wondering how long a 1 oz and 2 oz tank would run. I plan on 8x8 prop from recommendations.
Thanks,
Chris...
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Id guess 20 to 30 laps , on Niro , 15 % . AT A GUESS .
the ' Range Brews ' could double the laps , so say half of 70 ( laps ) on 10 % Nitro . = 35 laps . on a good day .
So posably 20 laps on 20 % nitro , with a head wind . S?P .
with the One Ounce 30 cc tank .
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Building a Long Gone VI my humble self at the moment .
Wings Done & crutch , tailplane etc. Bare Wood .
Lot of stuffing around , solid wing , for the internal leadouts etc .
Dunno if the OS 30 , H 29 R , or ST 21/29s going in it , yet .
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gotanypictures of yours .
p.s.
It might be easyer to fit one ounce in a two ounce tank , than fit two ounces in a one ounce tank . :-X
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Chris,
For reference, I believe that the B-TR rules specified a 30 cc maximum fuel load (tank plus lines, filter, etc.) Since the races were 35, 70, and 140 laps (qualifier, heat and final), everyone fiddled with venturi's and fuel mixes--sometimes between races--to try to gain advantage by eliminating a pit stop somewhere.
I have not run a McCoy. On the modern engines, 30 cc (1 oz.) was a challenge to always get the 35 laps. I couldn't run the largest venturi that would draw. I also experimented with "range mixes." Picked up some laps but didn't like the way it ran, so stopped doing that.
If you are doing a demo, and just want decent runs (a shade rich) without fiddling, just put in an oversize tank?
Good luck with yours!
Dave
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Thanks guys,
I am just messing around so if a 2 oz will fit that is what will go in it.
Chris...
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From my speed experience, I would suspect 90 to 120 sec on 1 oz with that set up. I'm basing that on 1/2oz would barely get you an official speed run, about 15 laps, I'd bet. So 1oz 30 3 sec laps.
Oops, math was off
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just read this post the McCoy RR will work good for TR but need to use a full body needle valve with a with a venture re stricter .
1 oz of 10 % should give u between 32 and 35 laps with the 8/8. are the motors ring or slug piston
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I'm building two Berkeley Minnows for a B Team Race demo and am using McCoy 29 RR redheads. I'm wondering how long a 1 oz and 2 oz tank would run. I plan on 8x8 prop from recommendations.
Thanks,
Chris...
I've found the McCoy RR .29 to be quite thirsty compared with an ETA .29, I've run both in the same B Class model/tank. The latter stock venturi gets 36 laps/30cc tank while the former is mid 20's. Changing the venturi hole would fix that.
An alternative is to add about 10-15% Iso Propyl Alcohol to the fuel mix. The least % that works is the best strategy. Modest volumes won't effect running. Normal 99% IPA from a Pharmacy or from a plastics sheet (Plexiglass) source should suffice. So say 15% Nitro, 20% Castor, 15% IPA and the rest Methanol. This would be a very mild range brew. BTW, the ETA started out as a McCoy clone but was developed much further.
Modern engines respond well to simply adding 10-15% Ethanol to the brew in place of some of the Methanol. Some countries now use 96% Ethanol (rest Methanol) as Mentholated Spirit, formally called "Wood Alcohol". Good for about a 10% increase in range.
Of course the simplest remedy is to increase the tank size a little :-)
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Thanks guys,
Bob do the regular mcCoy spray bars restrict them enough for suction opetation?
Chris...
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Thanks guys,
Bob do the regular mcCoy spray bars restrict them enough for suction opetation?
Chris...
No. One of the crew in Pullman, WA had a Mac .29RR in a TomTom. He had to put a Jim Walker pressure tank and regulator in it, to make it give a steady run. Otherwise, it was just plain bad. But I only saw it once, and never with the JW setup. It was loud when it was running strong. No idea what size prop he was running. I'd throw a 4mm spraybar through the stock venturi and run 6 oz of Coleman lantern fuel per gallon to start. You might need to add a filter or some panty hose mesh over the venturi to increase the suck. D>K Steve
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it will need the one piece spraybar .if this is just for demo flying I would restrict it until u get a good steady run .with an 8/8 it should still go fast enough .
if u set it up for case pressure it will really run good and is easy to work with
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Thanks Bob,
Robbed some 1960's .35 Stunt NVA's, got some cute 1 oz RC tanks, ground off enough stuff to fit the .29 RR Redhead into a Berkeley Minnow.
Chris...
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Now that is pretty cool. I didn't expect the formed aluminum cheek cowls. Nice!
I've been looking at a partially completed Redskin now for a week. I think it's going to have an OS in it. But no cool aluminum cowling pieces....
Divot
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Back in the days of B team race in Australia, the engines of choice were the ETA 29, McCoy RR 29 and Enya 29. I very much doubt that nitro was ever used because that would only reduce the range but petrol was quite often added at around 10% I believe.