This might be of interest for a Pattern plane, http://cgi.ebay.com/ws/eBayISAPI.dll...MakeTrack=true .

That does look like a nice engine. Notice they say it has more power than a modern .60. I still don't get it, why would there be less power today in a new engine instead of more?? That contradicts the nature of advancement. BTW I didn't notice if it has a pump or not.

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How many dedicated modern .61 size pattern engines do you know of being produced and sold today? None.

The old Rossi and YS engines were dedicated to doing just one thing, powering pattern aircraft, so their tuning was different. They were not limited to turning the huge pieces of lumber that today's folks call a prop in the name of reducing noise. They were allowed to rev up near 15k rpm where a two-stroke glow engine really begins to cook.

I don't doubt for a second that these same folks could produce a more powerful engine today, if they wanted to, but they don't. That's what he means.

I think that the "advancement" that has occurred during the past was caused by competition use. They were trying to squeeze every possible drop of power out of that given engine displacement, whereas a modern 10cc engine is simply just another engine size. They were also "pipe timed" which means that they were really designed to be run with a tuned pipe only.

It's notable that with the lifting of the displacement limit rule there is no longer the same kind of R&D going on by the leading engine manufacturers today. Granted they still aim at producing improved products, but there is really no need anymore to push performance to its limits when it's simply more practical to just bore out existing designs instead.

The primary goal today seems to be decreasing weight while increasing displacement. It's interesting to try and imagine what types of engines would be on the market today if the FAI had chosen to limit 2-stroke displacement to 1.20, for example, instead of dropping the limitation altogether.

As stiletto660 stated, the technological advancements that were the result of displacement limits made their way into sport engines over time. Today, the .46 has all but replaced the .40 and the .51/.52/.55 are in the process of replacing the .46s. The "just make it bigger" approach gives more power, it's true, but it does little in the way of driving technological advancements. On the other hand, maybe engine designers have gone as far as they can with glow technology, the same way full size prop-driven aircraft hit the speed wall. Bigger and lighter might be the only open path available in terms of advancement. I don't know.

Interesting observations rainedav, as just a casual observer of the pattern event for most of the last three decades (I flew a little pattern at the club level during the mid-seventies) I couldn't tell you if that's a better approach either. My guess though we be that if you had two different engines, and each produced two horsepower, the engine with the larger displacement will be "working" less and will generally last longer before something wears out or breaks. An extreme example might be the modern funny-car motors which are only good for one, quarter-mile zip down the track before a complete overhaul. I've only seen a couple two-meter planes at the field, I was amazed to learn they're only going through the maneuvers at about half throttle. The overall impression was that these machines were very refined, very specialized.

Neat stuff but not for me. To start a maneuver you need to be screaming out of a split S!



Bill Ervin (President, Cedar Yopantz Aircraft Co.)

Yeah, but can't they at least make a pumped .60? Even Jett doesn't have that. Is that what you guys rebuilding these old pattern plane use, the Jett motors? That seems to be the only real choice if you want serious power.

These OS 61 SF ABC-Ps work for me. One I bought new in 1991 and ran it for the first time last year in the Tiporare. The other two new ones I found on ebay.

I just bought three OS.61SF ringed side exhaust engines on eBay, with the same intention of putting them in older pattern designs.

I also have a YS.60 roundhead side exhaust and a Rossi AXE .61 side exhaust that I bought for those times when I want to let'er-rip with an 11x7 prop. Now to get some old pattern ships built in which to fly them.

I think I'm going to forego using a tuned pipe and just stick with the PSP and Jett mufflers. No disassembly needed when setting up and breaking down for transport. Getting lazy, I guess.

A .61 SF would be perfect, especially since it's a correct era motor. But now they command a premium "collectable" price on Ebay from what I understand. In addition, spare parts availability becomes a consideration. Is there NOTHING available new these days that can match a .61 SF's (or the Rossi originally posted) power/weight? That Tiporare is beautiful 8178.

Tommygun,

Thanks for the comment on the Tiporare! The SF ABC-Ps that I’ve bought on ebay were less than what I paid for my original in 1991. The first one was around $160 and the second was about $180. Don’t forget that Tower hobby repair has rebuild parts for the SF excluding the pump.

Yep, I just took care of the reserve price. Now let's see who REALLY wants it
Regards,
GPB

Rossi still makes 60 2 strokes that flat out scream. They make a short stroke version (32r60) and a long stroke version (154r60). One place to get them is here:
http://shop.vendio.com/RossiEnginesU..._cmd=1&categ=1

Same Guy that sells them on ebay.

what about the kraft 61,I thought it was designed for pattern back when.I always thought they had alot of power compared to other engines of the time,and equal to my os 61 fsr.

I don't know if it's being imported into the US, but Webra still has an RE .61:

http://www.webra-austria.at/motor.ph...r=AERO&lang=EN

I have three K.61s too. They are made by Mecoa and it is called the RJL K.61 http://www.mecoa.com/rjl/k61/k61.htm I like them because the have a small case and fit well in the classics. Pretty descent power at 1.8 HP. Most amazing is that Sheldons sell them for $120. They also sell HP engines http://www.mecoa.com/hp/61/2203.htm

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Are the OS pumps on the SF engines geared, or diaphgram? TIA

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I am surprised that it is a short stroke. Neat!

I had a Webra .61 Speed back in 81 or 82 that was a fantastic engine. Not ABC, it had a Dykes ring. Wish I had it now. Maybe I'll try to contact the last known owner. I don't think that anyone flew it after I had it. It was still nearly a new engine. It was side exhaust and very light weight. I did replace the Dynamix carb with an HB carb. No one ever told me that the Dynamix was intended to be ran with a pump! I got it to run, but it was always on the ragged edge of being too lean. It loved 5% nitro fuel too.

They are diaphgram pumps.

If you want a real screaming engine. check these out.


http://www.planethobby.com/product.p...6&cat=6&page=2

You guys should check the writeup by Steve Byrum in the SPA News Letter
called " Thrust? How I found out!! ". Go here

http://www.seniorpattern.com/newsletter/SeptOct2006.pdf

Ron