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Post  rsv1cox Tue Jan 03, 2023 9:44 am

Finished, or as far as I'm taking it.

OS/Graupner Wankel - It had to happen - Page 6 Dscn1924

Gave it every chance, lubed the sears and new springs, cross tightened the body machine screws, new gasket under the glow plug and still getting little to no compression. Maybe one day when I haven't much to do I'll load up some 25% with castor and lay an electric starter on it.

Bright side. I came up with a very nice OS .30 for very little money.
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Post  Levent Suberk Tue Jan 03, 2023 12:35 pm

About compression of Wankel engine:

https://ludens.cl/aeromod/wankel/wankel.html

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Post  rsv1cox Tue Jan 03, 2023 3:23 pm

Thanks Levent, good reading.  I may try his mixture although he did not mention proportions.  And, I may try his sanding upgrades?  Not much to lose.  I have to take it apart again anyway, found a shim.  

I'm comparing the compression of this one with my other two.  None have the compression of the OS .30 pictured that really has pop, or most any non clapped out Cox engine for that matter.  My other two at least have some compression, this one has almost none.  It started out with two strikes against it. Rusty "bore" with an area of rust bubbles.  Not good.  It will look good mounted in my RX-7.  Smile  Maybe make a hood ornament out of it.............double smiley!

The writers engine has the early? intake, kind of square without the air bleed.  All mine have the bleeds.

I ordered a bunch of M2's and M3's from China, dirt cheap with $1.99 shipping. Hex head, black.
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Post  GallopingGhostler Tue Jan 03, 2023 4:04 pm

That reading was informative and interesting, Levent. Appears that the writer may have a later PI-49 without the annular aluminum cooling shroud made with the old Meehanite iron rotor and carbon steel rotor (same tech as the pre-ABC / ABN engines). Instructions for earlier PI-49 version mentions running 25% all Castor oil fuel. I am wondering if the reason why he did not have initial compression for starting was use of a different oil mix or percentage. I think this is why they mentioned to use electric starter and to liberally flood all chambers with prime fuel before starting. Writer isn't clear whether he did that, IMO.

Once started and broken in, I'd think the surfaces would attain to a certain amount of polishing comparable to his "blue printing" methods. Anyway, that is my impressions, never played with one of these so only spectating. Horsing Around

eBay Just in, my latest McCoy .35 Red Head (missing needle) and 10 props in size 10x4. Engine has a decent T/F 10x6 with good red silk screening (mounted backwards as received). Got the 10x4's for use with .19 - .25 older glow engines.
OS/Graupner Wankel - It had to happen - Page 6 2023-012

Engine is bone dry, back plate screws appear extremely clean as though never removed. Plug was missing the copper or aluminum crush gasket. Backplate shows signs of running. Has some compression but plug isn't cinched down with gasket. Nylon crank throw spacer is intact. With a replacement mixture needle, new plug, and generous re-oiling may be a decent runner.

The clear plastic box is one the grocery store uses to sell the bulk items in. I removed the labels, just need to clean off the sticky label glue. Am toying with the idea that these could serve as inexpensive engine display cases (plus keep the dust off them), because they are stackable.

Off to do my own engine "blue printing". Very Happy
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Post  rsv1cox Tue Jan 03, 2023 5:26 pm

Novices with this engine must automatically think "no compression" as they are used to conventional glow engines. They flip it expecting the usual model engine compression backlash. Doesn't happen with these. You get something far more moderate. Doesn't distract from a different innovative approach for spinning a shaft.
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Post  GallopingGhostler Tue Jan 03, 2023 11:48 pm

Bob, thought you might be interested in this article on the Graupner Wankel posted on Page 13 of the April 1968 American Aircraft Modeler Magazine.
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