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Old Jan 25, 2016, 09:44 AM
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Sparkie with throttle


To again visit a subject I have enquired about several times over the past couple of years, I am still seeking to obtain a 10cc. or under sparkie that could be fitted with a throttle. It would be used to power a vintage model, Scram or similar, of 6/8 ft. span. In previous correspondence I mentioned a company that operated quite a few years ago converting glow engines, mostly Merco I believe, to spark ignition by fitting a Hall effect sensor into the prop. driver. I don`t know if this was ever a sucess, but it all seemed to disappeared quite suddenly! It should surely be possible to graft a carburettor, a super Tigre or similar onto an older sparkie which seem quite available on Ebay. I have access to some light engineering work. Has anyone done this with any sucess? or is there a better way to go? Previously I lost interest in this project and moved on to electric flight (really the most practical solution in these days!) but I still have the urge to recreate my youth, hear a slow revving sparkie pottering away and smell the burnt oil smell familiar to any modeller of advancing years! I would be most grateful to anyone who could help me in achieving this, or even possibly have something they would be willing to sell.
Thank you for reading this rather rambling request,
regards,
Bob Imp.
Here`s my current Scram flying on electric, also a New Ruler and Commodore just to show I`m not a dreamer!
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Old Jan 25, 2016, 12:46 PM
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Bob, coincidence, I've been running my McCoy 60 with an RC throttle this afternoon (a couple of hours ago). There will be a video of this on here in the very near future. I wanted to do one this afternoon, but the light wasn't good enough.
The McCoy would be superb in a Majestic Major.
When you see a McCoy 60 or an Ohlsson big port running with RC throttles, there's not much point in messing with modern engines (for me, anyway). They start immediately, they're powerful and they run forever on a very small tank of very cheap fuel.
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Old Jan 25, 2016, 04:48 PM
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I have seen Ohlsson sideports with a carb added, and the worked great. Once in a while an Anderson Spitfire shows up on ebay with a throttle. When McCord took over the Spitfire they produced one version with a carb. I usually just fly mine climb and glide, but it would be neat to have a throttle for just flying around and low throttle. I sometimes fly my PlayBoy Sr. with a Saito 56 four stroke, and just put around with that, but as you say it would be really fun with a sparker.

I made a timer for my OS 60 open rocker four stroke, but as yet have not made the cam. Getting lazy in my old age just do not get the things done I use to. LOL

With the governments intrusion into model aviation I may just stick to control line if they are exempt. I have 5 of those set up with sparkers. Lots of fun.
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Old Jan 26, 2016, 09:33 AM
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I sure do admire whoever did this large port Ohlsson conversion - a different way to get a throttle.

Jim
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Old Jan 26, 2016, 11:33 AM
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Originally Posted by jjscott View Post
I sure do admire whoever did this large port Ohlsson conversion - a different way to get a throttle.
Jim
That's very impressive work, but I think it's overkill.
This one runs superbly, with a very low, steady idle, just with an RC carb stuffed in the air intake. The throttling is as good as any normal RC engine. The low idle is helped a lot by the spark of course.
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Old Jan 26, 2016, 11:36 AM
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That's very impressive work, but I think it's overkill.
This one runs superbly, with a very low, steady idle, just with an RC carb stuffed in the air intake. The throttling is as good as any normal RC engine. The low idle is helped a lot by the spark of course.
That`s exactly what I had in mind! Have you just connected the carb. to the intake with silicon tube?
Bob Imp.
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Old Jan 26, 2016, 01:00 PM
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No Bob, the carb is an exact push fit in the intake tube. The silicon tube that you see is only blanking off the original holes, where the spray bar went through the intake tube. I'll do a video of this as well. I've been waiting for weeks to get reasonable light for a video. It'll happen soon...
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Old Jan 26, 2016, 01:24 PM
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Bob, there were also a number of modern loop scavenged OS and other brand engines converted to spark for use in the SAM events. But having heard a few run I think you're on a better road in trying to throttle one of the old mills. The new ones rev higher and sound like a modern glow engine but with a rasp to the note. The old originals sound far more thumpy and just "righter" for what you are trying to do.

The neat thing about that side port mod is that none of the original engine is modified. Although you WOULD have a nicer and more reliable idle if you can figure out how to retard the spark a little for when you select lower throttle and idle. So if that side port with the settable spark timing could be combined with a throttle carb I suspect that a lovely smooth idle could result. Otherwise the spark will be occuring far too soon before TDC to get a nice SMOOTH idle.

A Brown Jr or replica also uses the same sort of tube. The worst issue might be to find a carb with just the right size stub. But if it comes to that I'm sure there's some home machinists out there that could help you out.
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Old Jan 26, 2016, 01:31 PM
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Yeah, I didn't mention that but, as BM says, neither the Ohlsson nor the McCoy are modified in any way. You just add the appropriate carburettor, and you can return the engine to its original configuration whenever you want.
I have three old sparkers with throttles. The McCoy and Ohlsson shown here, plus a Forster 99 on which the timer-operated throttle is original. And all three work very well indeed.
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Old Jan 26, 2016, 02:16 PM
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Quote:
Originally Posted by brokenenglish View Post
No Bob, the carb is an exact push fit in the intake tube. The silicon tube that you see is only blanking off the original holes, where the spray bar went through the intake tube. I'll do a video of this as well. I've been waiting for weeks to get reasonable light for a video. It'll happen soon...
This is the way to go if you want to add a carb and keeping the engine original if wanted later on
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Old Jan 26, 2016, 03:56 PM
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Another thought about the Ohlssons. Back when I was collecting engines there were a lot of side ports where someone either shortened or angled the intakes. These didn't have much value to collectors but would be perfect for carb conversions. Whether they show up on ebay, I don't know, but they should be cheap and it wouldn't matter much how the r/c carb was attached.

Jim
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Old Jan 26, 2016, 04:13 PM
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Jim, that's exactly what happened to me!
About 10 years ago, just messing around, I discovered that one of the RC carbs in my box of bits was an exact fit in the Ohlsson "big port" intake.
That was "interesting", but I didn't do anything about it.

Then, a few months later, there was a "big port" offered for sale, virtually new, except that some clown had shortened the intake. I bought it for a fairly modest price, with the idea of trying it as an RC engine, and that is the engine shown in my post above. It runs and throttles superbly.
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Old Jan 26, 2016, 07:41 PM
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A club friend of mine has been flying an Anderson Spitfire sparkie with an R/C throttle for many years. In order to get decent throttle control he had to cover the sub piston induction openings. Not an issue for engines without sub piston induction.
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Old Jan 26, 2016, 08:49 PM
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I cover the induction holes on all of my sparky control line engines as it gives them better fuel draw and much steadier running. Just a piece of gasket material or tank tin cut to fit around the cyl. with a plastic tie works fine.

At one time Saito made a sparky with a throttle. They generally bring big money though.
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Old Jan 27, 2016, 02:50 AM
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I cover the induction holes on all of my sparky control line engines as it gives them better fuel draw and much steadier running. Just a piece of gasket material or tank tin cut to fit around the cyl. with a plastic tie works fine.

At one time Saito made a sparky with a throttle. They generally bring big money though.
The Saito G-60
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