Just Received 2 Cox 290 Engines

Marleysky wrote:Well, you sure have some nice thoughtful, generous friends. Did they trash the planes? Seems I read somewhere someone was looking for a sportavia. Everybody wants a Corsair!  

Marleysky, he's had these engines for a long time. Both planes were crashed and trashed years ago, this is all that is left. The Sportavia white back engine with aluminum needle is missing the venturi screen and doesn't have the typical heat pressed crimp marks of the Sure Starts. I'm thinking it may not have had a screen; perhaps obtaining "prefiltered" combustion air from the inside of the fuselage? Looking through the venturi, I can see where it is slightly squeezed off by two flat flanges like the Sure Starts to provide a restriction. With screen off, it is begging to be drilled full open.

Needles are not the fine thread earlier versions like with the postage stamp and early Sure Start type venturi backs. Sure Start needle fits both.

The Corsair black back engine has a contrary left hand prop and spring starter, but an aluminum prop drive plate. Did Cox use left hand props on some of their RTF aircraft to help maintain line tension?

I've always wanted a left hand prop start assembly, now I have it.

Hi George, I suspect we have the same white ones. I think these may be a better-grade plastic than the later ones. Mine (below) never had a venturi screen that I can remember.. either. It too was given to me as an orphaned engine. I don't know from which model.. but there were more than a few, that had these back-plates. The Alum. needles are the same 80 tpi as the Brass.. and Bernie sells them both.




The Postage Stamp back-plates (not shown) seem like a much more dense plastic the later horseshoe-style.

Thanks, Roddie, so I'm not alone on these white horseshoe backs without screen. The needle on the black horseshoe back was bent about 3 mm, with a little careful persuasion I rebent it straight. These don't have the plastic knob cap at the end of the needle. There's no score mark on the needle head to use as a number of turns counter. I gather that the plastic cap must have been lost somewhere during its history. That won't prevent me from adjusting them, just score the top with a file.

The more dirty white horseshoe back engine will require cleaning to free it up for rotation. The black one has plenty of compression, typical Leisure Dynamics Cox quality. The $7.00 US Sure Start I bought from Estes closeout has weak compression.

Just out of curiosity, I squirted drops of light machine oil into the gummed up Sportavia donor engine. Working the prop back and forth, freed it up. It now spins freely and has plenty of compression. When I get a chance, will disassemble, thoroughly clean it, reset the piston con rod socket. One thing for sure is I have a good solid engine with like new compression. It's just begging for a candidate for installation. Compression is quite in contrast to the low one with the new $7 Estes Cox Sure Starts.

That "horseshoe" back plate also fits the Cox Fokker D7.





This strange assortment of parts came with two engines both with "postage stamps" neither one fit.  I just happened to have a spare horse shoe.  The grey backplate fits fine but the relief for the reed is to shallow to accept it.

That is interesting rsv1cox. It sort of puts a date on the engine, I imagine 1980's vintage; nice potentially restorable Fokker D-VII, too.  

I cleaned up the engines first by soaking in Acetone and brushing with a toothbrush to remove glow grime. Reset socket joints prior to reassembly.

Sportavia engine had serious aluminum pitting on it. I gather that the engine may have spent some time outdoors, perhaps lost until someone found it, or was exposed to the elements in say in a box in a carport at a say oceanside location. If you can't make it look original, make it look better than original.  

Mothers Aluminum Polish removed the bad tarnish on the crankcase and prop drive plate. Attempting to remove surface rust removed some of the black blueing finish from Sportavia engine. I made apple sauce out of bad apples by installing an Ace R/C exhaust throttle sleeve. It started life as an RC plane engine, now it can relive as an RC engine.  



The Corsair engine appears to be a very low time engine, after cleaning, it looks brand new and has new like compression. I imagine it didn't take many flights for it to become a donor engine.

GallopingGhostler wrote:


The Corsair engine appears to be a very low time engine, after cleaning, it looks brand new and has new like compression. I imagine it didn't take many flights for it to become a donor engine.

George, You may want to put a L/H prop on that engine.. or a R/H starter-spring.

roddie wrote:George, You may want to put a L/H prop on that engine.. or a R/H starter-spring.

Roddie, I've got the prop on backwards for a pusher. I want to retain the left hand starter spring. My thoughts are to install it on my Estes Cox Star Wars Y-Wing aircraft kit. It uses a pusher configuration. Then I can continue to use right hand props without having to resort to purchasing left hand ones. About the only upgrade that would be worthy is replacing the aluminum prop drive plate with a brass one from Cox International or EX Engines.

George, if you want to restore that rusted cylinder finish go to brownells.com and get some of this:



Clean all the rust off as you already may have done. Immerse the cylinder in the liquid (I use a small fruit cup) for about a minute, wipe dry, do it again. Rinse with warm water, neutralize with baking soda, burnish with a tooth brush, spray with RemOil and enjoy a new looking cylinder.

Bob

GallopingGhostler wrote:

roddie wrote:George, You may want to put a L/H prop on that engine.. or a R/H starter-spring.

Roddie, I've got the prop on backwards for a pusher. I want to retain the left hand starter spring. My thoughts are to install it on my Estes Cox Star Wars Y-Wing aircraft kit. It uses a pusher configuration. Then I can continue to use right hand props without having to resort to purchasing left hand ones. About the only upgrade that would be worthy is replacing the aluminum prop drive plate with a brass one from Cox International or EX Engines.

 well.. that would certainly make sense! Speaking of drive-plates.. I was looking at my cam-style starter-springs.. and most that I have seen are designed to fit the hex drive-plate. I bought a couple of L/H starter springs last year from a hobby shop that was going out of business.. and just noticed that one is solid.. without the hex molded-in, so it can be used on a round drive-plate.

It's the same Cox (#334) part though.

Roddie, I believe the one with universal plastic spring drive plate is the earlier one. This type came with my R/C Bee engine I purchased in the late 1970's / early 1980's time frame. Earlier engines I bought only a few years before had the frictionless snap spring starter. Later engines came with the hex shaped prop drive plate, which the cam'd version fits onto. The Corsair donor engine has this style but in the left hand.

Why Cox retained the same part numbers, I don't know. Perhaps it is just one of the signs that expertise at Leisure Dynamics moved on and left those managing who could care less? I'd expect caring managment to catch little errors like that, before they happened.

In a way there is a slight disadvantage to these type spring starters, AFAIK they rob the engines of a few hundred RPM.

rsv1cox wrote:George, if you want to restore that rusted cylinder finish go to brownells.com and get some of this: Clean all the rust off as you already may have done.  Immerse the cylinder in the liquid (I use a small fruit cup) for about a minute, wipe dry, do it again.  Rinse with warm water, neutralize with baking soda, burnish with a tooth brush, spray with RemOil and enjoy a new looking cylinder. Bob

Thanks Bob, I wondered what to use this day and age, now I have the answer.

As Roddie's photos show and what I found out after engine disassembly, the venturi backs of both engines do not have the flat sided air restrictions on the venturi exit hole as on the Sure Start engines. The dual slit exhaust cylinders also have two very large bypass flutes machined in them, which I imagine is to help make up for power by not using subpiston intake air induction. These appear to be decently powerful sport reed engines a touch better than Sure Starts.

With the mufflers I just purchased from Ron Cribbs (thank you, Ron!), by putting the exhaust throttle muffler on one would make it an ideal candidate for a Cox .020 Tee Dee powered aircraft. One such that comes to mind is Ken Willard's Tee Dee .020 powered 30" span undercambered sheet wing Virus aircraft, but there are others.

It's original guidance was a single channel compound escapement radio with cellular phone type texting to the only "stick", a push button transmitter switch. Sample sequence, which resulted in full elevator / rudder throws is as follows: 1 hit/hold=right rudder, 2 hits/hold=left rudder, 3 hits/hold=up elevator, 4hits/hold=down elevator, release=neutral. To do a smooth altitude retaining wide turn, one would pulse it temporarily every couple seconds (hence why I call it texting, .

Outerzone: Ken Willard Virus 1964 RCM Plan




I don't intend to mislead anyone as I haven't yet settled on likely candidates to put these engines in yet. I just gave an example of what I though would make a good candidate.