Dieselizing a Baffled Engine

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Dieselizing a Baffled Engine

Postby giffy » Sun Dec 05, 2004 10:19 pm

There are a few engines I would like to try as a diesel but, they have baffles on the piston. I have a few ideas on what to do but, has anyone tried this before?


Giffy 8)
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Postby Rustler » Mon Dec 06, 2004 4:40 pm

The O.S. 15D used this system. I believe it used a keyed contra-piston, so the groove for the baffle stayed in alignment. The King Cat 1.5cc diesel used a flat top piston with straight cut ports, which ran but was not really succesful. The glow version with the baffle was far superior. Possibly the most succsful is the Super Tigre with flat-top piston and angled transfer ports, but of course, if you want to keep the baffle, you need to key the contra somehow. Good luck,
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Postby 1705493 » Mon Dec 06, 2004 7:15 pm

I've got a Veco .19 that has a baffled piston and I think there's a way to dieselize it without keying the contrapiston or slicing off the baffle. Working on it and will let you know how I make out.
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Postby Jim Thomerson » Mon Dec 06, 2004 7:18 pm

I think you could make a contrapiston which would extend up into the head, above the top of the cylinder. You could then cut a vertical slot in the top of the contrapiston and insert a roll pin through the side of the head to key in the contrapiston. Another way would be to drill a vertical hole in the top of the contrapiston and insert a roll pin. This would stick up through a hole in the head with free clearance. On first pass, it doesn't sound too hard to do.

Jim
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Postby 1705493 » Mon Dec 06, 2004 9:57 pm

Thats a good idea Jim,

If my attempt doesn't work, I'll give it a try.

Andy
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Postby giffy » Wed Dec 08, 2004 5:31 pm

I was thinking of a smaller counter piston that would fit inside the baffle area. If the compression ratio was close to being right then you wouldn't need much adjustment.

Possibly an offset counter piston?

I was also thinking of a head that had no counter piston you could make adjustments with fine head shims. It would work ok if you always use the same fuel, prop, ect.

The anti-rotation pin idea is interesting, I'll have to draw some pictures.


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Baffle piston diesel

Postby diesel_don » Thu Dec 09, 2004 6:00 pm

There is also the OS 2.5 cc 2 BB side exhaust with baffled piston( of which, I'm a proud owner) though I have no idea how OS keeps things lined up. The Enya apparently had no problems as they produced a Mk 11 a few years later ( inexplicably NFFS Nost legal!) The Mk 1 was questionable (1957?), second version all new! way beyond the criteria, but then once you move engines off the ineligible list, blatantly as with the COX Olympic guess any thing goes,( and you don't get to vote on it !) Cheers d-d
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Postby giffy » Sun Dec 19, 2004 9:15 pm

1705493 How are you making out with that Veco .19 ? I was looking at mine and, I don't think the crank web will hold up to the diesels compression.


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Postby CharlesF » Sat May 27, 2006 3:22 am

Best idea is to use a vertical pin passing though the top of the head to keep things in alignment

You need to keep the head shape optimum, so a small contra-piston is not such a good idea. Also you need a fairly wide adjustment range because compression varies with weather conditions, fuel and of course prop used.

It is also essential that the bottom end can take the added stress of a diesel, con rod, crank pin and web must all be substantial.

I dieselised a K&B .15R many years ago for teamrace - worked very well.
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Postby 1705493 » Sat May 27, 2006 10:04 pm

giffy wrote:1705493 How are you making out with that Veco .19 ? I was looking at mine and, I don't think the crank web will hold up to the diesels compression.


Giffy 8)


Giffy,

You're right and somehow, I never got your message. Then again, I should have got back to you guys. Ma fault, en Francaise, my bad in English.

Anyway, I covered the project at RCU here,

http://www.rcuniverse.com/forum/m_23821 ... tm#2695737

As mentioned, it works but I don't know how to compare the performance to other diesels, conversion or OEM. Still, it was fun trying and I may fly it in a biggish Cub or something someday. Too many engines, not enough airplanes.

CharlesF

Thanks for reviving this thread and reminding me that I owed a report. You're right about a small CP, it doesn't seem optimum. And yes, a tweak of the tommybar doesn't work here. You really have to crank the CP to get any effect.

Next time, I'm going to run the engine as glow, get some numbers and then run it on diesel with the same prop. No team racing but in this case, the engine, on diesel, with a small prop just might be stronger on the verticals compared to glow.
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