Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

OPMDS .61?

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Old 02-02-2013, 06:56 PM
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MJD
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Default OPMDS .61?

I was rooting through my newly organized engine drawers today and sorting out some bins containing parts of engines in various states of dis/reassembly. I noticed a close similarity between the front housing of my MDS FIRE 10cc, and OPS Speed .65. After some curious fiddling around, I find that the OPS .65 rear rotor assembly and front housing are a perfect fit, and I mean gasket free clearance fit, into the MDS crankcase. The bolt holes line up. On top of that, the OPS crankpin fits the MDS rod perfectly. I guess if you're going to copy something successful the OPS is a good place to start. There is more than coincidence here I think. The only issue so far is the piston skirt needs a slight cutout to clear the rotor assembly at BDC, but this is a subtle difference and could be remedied in minutes via a tiny bit more relief on the rotor housing.

Not that this would serve any useful purpose, except, if someone really liked the performance of the MDS top end and wanted to make a tougher sport engine they could push in to the higher teens but were nervous about the reports of a weak crank, I suppose this is a way to achieve that. It would help to know someone who has a box of AMA D speed engine parts they've gathered over the years.
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Old 02-10-2013, 02:50 PM
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Default RE: OPMDS .61?

Well if you have an OPS rire engine in your parts box, and a bunch of MDS 60's, this is a good place to start cutting things up if you ask me.

Too bad you found out after the MDS went out of production like 10 years ago! :-P

The main case is really not critical, neither is the liner... so you just need a new head to make a real strong performer if you wanted to.
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Old 02-10-2013, 04:44 PM
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Default RE: OPMDS .61?

This MDS was made in 1989.

Again, there is no real reason to do this, I just found it interesting that the fits were so perfect.
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