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[Rusty]

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[George Albo]

His name is Bjorn Baal. His email per Frank Bowman is rmjmachineworx@gmail.com.

Write him and let us know.

George Albo

[Lauri Malila]

I partially agree with MM.
But I don't say that there is a real quality issue. In my opinion, it's nearly impossible to get perfect results by just buying a stock ring and expecting that it will have exactly the correct dimensions.
Every time I have sent my piston/cylinder group to Frank for fitting rings, the result has been perfect. Then, when his rings become unavailable for a while, I got some of his last stock. As I expected, they were un-usable, not up to my standards.
Maybe it's more critical with my AAC cylinders but the ring must be fitted (outside turned) to fit individually to each piston/cylinder group. by experimenting I have found best results with ring o.d. (Compressed) that is 2 microns (that's about 0,00008") less than cylinder bore ø.
I do the final o.d. after heat treatment, in a special holder to keep the ring in compressed state.
Done like that, the engine only need a few minutes of running in. If it needs more, the ring has propably deformed during installing and it's better to install a new ring after refreshing the chrome honing.
But with steel/iron engines it's propably more forgiving.

L

[frank mccune]

        Ni Lauri:

        How do you measure to 5 places?  I am happy to measure to 4 places with hand held measuring instruments.

         All I can say to your machine work is WOW!

                                                                                                      Be well,

                                                                                                      Frank McCune

[Brett Buck]

This thread explains why the ABC/ABN/AAC cylinder/piston system is one of the greatest breakthrough in stunt engines since the Fox 35.

    Brett

[Lauri Malila]

Frank,

I have good tools, not a problem to get repeatable results with them and some experience.
Brett, I guess you meant to say biggest breakthrough from crappy quality engines ?
I know it's not worth trying to convinvince people here but I strongly believe that a well made ringed setup can be better. It's just that such haven't really existed in this type of engines before we started this with Robbie.
And it's not only about ring but having the whole package right.
The mainstream Jetts, PA's etc. are good because that's the technology they master. But you also must remember that it's the technology made obsolete by MB's with integrated costruction and that's what we are adapting to stunt now. It would be easier to make it without ring. But not better.
L

[Brett Buck]

And it's not only about ring but having the whole package right.
The mainstream Jetts, PA's etc. are good because that's the technology they master. But you also must remember that it's the technology made obsolete by MB's with integrated costruction and that's what we are adapting to stunt now. It would be easier to make it without ring. But not better.

  I don't know what "MB"s are.

    The problem is illustrated abundantly in this thread - you are talking about measuring to microns or rejecting the parts. I don't know what you do in Finland, but I don't carry a precision machine shop to the soybean fields in Indiana. We have people talking about not being able to get parts for STs and K&Bs, and no one being able to make acceptable parts. While there may be some other issues going on here, I know I have worn out exactly 2 ABN/ABC/AAC cylinder/piston assemblies in the last 27 years, both after flights counted in the thousands. And I won one fo the most competitive contests in the world *after it was clearly on its last legs*.

    It was a great year if you got through an entire season with a single ST ring and acceptable power, and many times they lasted weeks. Replacement parts wouldn't be necessary if didn't wear out (again, in terms of *microns*) in the first place.

     Requiring hyper-precision fits and extreme care that is almost impossible to achieve is not an indication of superiority, it indicates a fragile system with no robustness.

   All I know is that I spent endless hours screwing around with engines, rings, brake cylinder hones, in the hot central valley Sun for hours when I had ringed engines. When I got an ABC and later AAC, I stopped having to do that, and forgot about wearout and "what the heck happened to my engine this time" problems that were rampant at the time. I make changes to make it run differently, if you leave it alone, it runs the same.

     Brett

     

[M Spencer]

There a method of holding the ring between two wooden dowels , of the Dia. of the bore ,

and lapping the ring to the bore .

ETA 29s were advetised as ' lapped ' . Unless it was the rotor to the backplate , presumeably He lapped the Rings to the Bore .

Flat on a glass plate or 1200 wet & dry , and maybe ' removing the hard edge ' on the inside dia ? might be of some use too ,

If stuck with non - fit off the shelf  - items .

[Lauri Malila]

Brett,

MB.40 is an F3D engine of Rob. It has dominated the category for over 10 years now. Powerwise it's more or less the same as best Nelsons but it can tolerate all the loads much better mostly bacause of a monoblock cast cylinder. Google it, it's quite interesting.
What I do is like early MB's or any modern F2C engine, a monoblock cylinder but fully machined instead of bypasses & ports integrated in casting. Maybe in future I'll go to cast cylinder too, that would be cool.
Please try to understand that your bad experiences with ringed engines are from an era of bad engine metallurgy. And castor oil. ST's and such are as you said; they work ok if you know what you are doing and keep working for them. What I have has much better materials and tolerances. Ring is the least of my worries, it will not wear out or cause other surprises for many years. I have one piston/cylinder group with a std ring with about 1000 flights and it's still as new, ring gap is still the same 20 microns and I can still see the lathe tool marks in the o.d. of ring. And my new Dykes rings are even better, with more surface area and less surface pressure. Good grey cast iron against good chrome is friction-wise about as good as it can get.
With ring, I can basically forget the the critical issues of aac- and abc, cylinder cone and piston fit, they are more difficult to master and repeat.
Good ringed setup is also difficult to make but not in same way. All the machining is more complex and it has to be made very accurately. It's not possible in mass production. L

[Brett Buck]

Brett,

MB.40 is an F3D engine of Rob. It has dominated the category for over 10 years now. Powerwise it's more or less the same as best Nelsons but it can tolerate all the loads much better mostly bacause of a monoblock cast cylinder. Google it, it's quite interesting.
What I do is like early MB's or any modern F2C engine, a monoblock cylinder but fully machined instead of bypasses & ports integrated in casting. Maybe in future I'll go to cast cylinder too, that would be cool.
Please try to understand that your bad experiences with ringed engines are from an era of bad engine metallurgy. And castor oil. ST's and such are as you said; they work ok if you know what you are doing and keep working for them. What I have has much better materials and tolerances. Ring is the least of my worries, it will not wear out or cause other surprises for many years. I have one piston/cylinder group with a std ring with about 1000 flights and it's still as new, ring gap is still the same 20 microns and I can still see the lathe tool marks in the o.d. of ring. And my new Dykes rings are even better, with more surface area and less surface pressure. Good grey cast iron against good chrome is friction-wise about as good as it can get.
With ring, I can basically forget the the critical issues of aac- and abc, cylinder cone and piston fit, they are more difficult to master and repeat.\

    Rob?

      That may all be well and good, but if you design something that can't be practically manufactured, for all intents and purposes, it's a dead end. And it was my (and many others) experience that manufacturing ringed engines to the required tolerances required extensive hand fitting that, in practice, couldn't be reliably achieved. ST couldn't manage it reliably, McCoy (with an even cruder dual-ring system to try to make up for manufacturing weaknesses) couldn't manage it, there are two active threads about K&Bs with bad rings and how they can't be replaced. I am very impressed at your work and that you can make it work  - although I am not aware of how much has been done to develop as a stunt powerplant, or what the repeatability or durability might be over a few thousand flights.

     On the other hand, until very recently, I could go get a 25LA for as little as $60, do a 500+ point official flight *on the first run out of the box*. It's predecessor the 20FP was $49, did the same thing, and then I ran the silly thing for the next 20 years with no maintenance whatsoever. I put it in the airplane in 1996, and it worked perfectly when I last flew it in *2016*. Same with it's big brother the 40VF - I got an engine and pipe for $125 after someone had concluded it was "worn out", then proceeded to run the thing in about 100 contests and thousands of flights from ~1990-1997, including qualifying at the US Nationals 5 times in a row.  That one, I finally did wear out, so I grabbed a brand new one out of the box, bolted it in the airplane with the same setup, ran one tank of fuel through it on the ground - then came in second at the NWR after having tied with Paul Walker in the first round - with ZERO flights on the engine. and 5 flights total in the preceding year.

[RandySmith]

My  AAC  setups on the  PA  engines , Aero Tigers , HPs , OS VF  and  SF  engines  last a VERY   long time.  I have many people that have pushed near 3000 flights out of 1 set, others  Like Dave Fitzgerald  for instance handed me  his  PA 61 at the NATs  for rebuild  after  over 2500 flights, and it was  still running well.
I also  know  of many PA 40s and  Aero Tigers    that are way over 2000 flights and still going strong, some of these  have worn out the bearings , had them replaced  using the  original piston sleeve,  So I am very partial to  AAC  engines , and would never venture into making them ringed  engines for  production .

Randy

[Steve Helmick]

Pretty sure that "MB" and "Rob" refers to Rob Metkemeyer (Netherlands). I think the "B" is for "Brothers". The Metkemeyer Brothers (Rob and Bert) were a World Champs class F2C team, who made their own engines. I recall that they were proponents of using a steel front bearing housing to match the expansion rate of the steel crankshaft. They also make/made the best FAI Pylon racing engines...F3 something or other, IDK.

Bert, IIRC, also flew some stunt, and designed the "Trianic" (no, not "Titanic"). The "Trianic" was shown in Tom Morris' book of Classic Stunt Designs. It was then published in Flying Models and flown at VSC by Alan Brickhaus about 2010 or so.    Steve

[Lauri Malila]

In my first posts, before it went off-topic (sorry for my part) I was just commenting the overall quality and bad metallurgy of the engines Brett dislikes, I think stupid to doom the whole technology because of those bad experiences. I never compared the wear with other technologies, just between a correctly and wrongly made units.
We chose to use the ring (that sounds like JFK) and get rid of drop-in liner because it makes sense to us. Them both details give a clear advantage in thermal stability.
Regarding the mass production, I don't care. But why it would be a dead end? We have learned a lot and proved wrong some old mis-information. And it's a good engine, too.
We keep making them for myself and some very selected people who respect and see the potential in our work, understand the risks and won't become a pain in ass later on. In short, friends.

L

[RandySmith]

In my first posts, before it went off-topic (sorry for my part) I was just commenting the overall quality and bad metallurgy of the engines Brett dislikes, I think stupid to doom the whole technology because of those bad experiences. I never compared the wear with other technologies, just between a correctly and wrongly made units.
We chose to use the ring (that sounds like JFK) and get rid of drop-in liner because it makes sense to us. Them both details give a clear advantage in thermal stability.
Regarding the mass production, I don't care. But why it would be a dead end? We have learned a lot and proved wrong some old mis-information. And it's a good engine, too.
We keep making them for myself and some very selected people who respect and see the potential in our work, understand the risks and won't become a pain in ass later on. In short, friends.

L

Hi Lauri   my post was  not  an attack on your take on technology or your  engines, your work is outstanding , I have made ring setups that work extremely well, and last a long time , but... they are   WAY more expensive to make and more time consuming to put together and run  in. The  AAC ,  ALUMINUM case   , aluminum  sleeve, aluminum  piston, are  ALL made of Aluminum, and the rates of expansion in the motor  is very good and very close to each other, and  is a World Class  design  and  last an awfully long  time, that with the cost being lower  makes it sill to  try to make production engines that are  much more expensive to make....   That was  my point, I realize  there  are other ways to do things

Randy