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"Cox Medallion .049 R/C"

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My Contestor & O&R Sparkers

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My Contestor & O&R Sparkers

Post  wha-tah-hey on Sun Feb 12, 2017 12:56 pm

Not much activity here so I'll inject a little fresh discussion.

These are my 1946 Lucas & Smith Contestor D-60-R and 1948 O&R .60 Special ignition engines.
L&C (a Cal auto parts mfr) made only the ringed .60 cu in Contestor for only that one year, but in both a much more rare sideport (D-60-S) and this not-too-common RR version, beautifully made but not as powerful as most contemporary .60s.
I've removed the rear tank on this one.

The common as rocks O&Rs, both sideport and FRV in various displacements, all lapped piston, are also very well-made. They do have the unfortunate spot-welded cylinder assembly, making them less robust than other popular rivals though capable of running way beyond what is healthy for them.
A PO had rigged a baffle on that HUGE (even with the insert) venturi so JB Weld proved useful, and I have a temp OS remote NVA on it which works just fine on the bench.

These both run well for their types on either 3:1 glow/castor or 3:1 gas/castor and they can be run as pure glow engines by merely replacing the spark plug with a glow plug. Fuel type makes little difference in performance (+ 2-300 rpm on average for methanol). Gasoline gives a good bit better mileage but is more needle sensitive.
More than 5% nitro isn't recommended and is usually not needed. Ignition engines, like diesels and 4-strokers, are at their best driving relatively large props at relatively low rpm, depending on torque rather than sheer horsepower.

Some representative bench results:
10.2K 12-4 APC
9.2K 12-5 APC
8.8K 12-6 Zoar or Vess wood
8.1K 13-6 APC
7.9K 13-6 MA
6.8K 14-5 Zinger wood
10.8K 12-5 APC
9.5K 12-6 APC
9.0 13-6 MA
9.3K 13-6 APC
7.9K 14-5 Zinger wood

With heavy pistons and not enough crank counterweight, they DO vibrate, so tie 'em down real good.  Thumbs Up
One day I may build an OTS stunter or two to get 'em back in the air.

For your enjoyment (if you LOVE bench running), an early '50s comment on breaking in an O&R .33:


Last edited by wha-tah-hey on Sun Feb 12, 2017 6:16 pm; edited 1 time in total
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Re: My Contestor & O&R Sparkers

Post  balogh on Sun Feb 12, 2017 2:25 pm

With 3:1 gas or glow to castor ratio do you mean 25% castor content? I thought gas model engines run on 1:40 or 1:33 fuel like lawn mowers or chainsaws..
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Re: My Contestor & O&R Sparkers

Post  wha-tah-hey on Sun Feb 12, 2017 3:07 pm

Yes, I run 25% castor but there are options.
Originally (and still by some) ignition engines were run on gas and 70 wt motor oil, either 25 or 33% oil.
70 wt is hard to find these days and some run the more readily found 60 wt in those proportions.
Note that silicone tubing degrades and should NOT be used with gas, nor glow fuel in the plastic tanks of old engines - it'll melt 'em in short order.
Jim Kraft, a very successful OTS flier, has switched to 25% Wal-Mart 2-stroke oil only in his many sparkers, to his satisfaction.
Many also run the more highly refined Coleman fuel in lieu of pump gas (universally recommended to have NO ethanol content) which is subject to variations in actual chemistry around the country and in different seasons.
However, ethanol is merely another alcohol like the methanol in glow fuel. Alcohol's basic problem is that it's hygroscopic and weed-eater, etc., engines need an after-run oil treatment to prevent internal rust if run on E-10, just as glow engines run on all-synth fuel do.
I haven't run any, but regular E-10 pump gas SHOULD actually be fine in a sparker when mixed with at least some castor to provide anti-rust protection.
FWIW, though I don't fly 'em yet, I use a modern metallic film capacitor (the little rectangular brown and blue thingies in the pix) and a single 1500 mah LiPo cell for lighter weight.
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