Run in stand/dyno build.

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Terry Keeley

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Look great Terry, what kind of needle valve is that in the last picture?
Carl Brey, CB Marine. He made some cool chit back in the day, carbs, exhaust throttles etc.

This is the simplest needle I've ever had, tapered 4-40 needle, 2-56 to hold it in place.
 

Terry Keeley

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Found out today the themistor sensor under the glow plug is very close to the IR gun, I'm reading it with the Eagle Tree so far as my Datamite needs an adapter for it. Got up to about 160F which seemed fairly hot to the touch, I'm starting to question that 160C figure from the Nova Rossi video. I'm using a needle valve to control the water which works very well.

Vids are long, can't find good editing s/w free...





Forgot to run a filter on the pressure line and got a sliver of carbon in the needle, it goes lean and takes the plug at 1:55:






Broke the 5/32" tool blank pin at 2:12:









It got hot after it broke and spun a bit. Thinking to make another out of S7...
 

Glenn Quarles

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This is a fantastic thread! Terry it is always fun following your projects and the expert advice you get. Well done!!

And yes the 160C from the Nova break in is about right! I spent an hour in that booth watching with my own eyeballs! That motor was SMOKIN HOT!! The entire piston top to bottom (except for the very small seal area by the oil grooves) was absolutely pitch black (burned on castor). After the break in and test runs were done we let the motor cool for awhile before taking it off the test stand...he handed it to me and it was impossible to hold without a glove or doubled over rag! Every piece of metal on that motor would burn if it touched bare skin! We are used to getting the heads on our motors warm, but nothing like I saw there.
Keep up the good work!!
GQ
 

Terry Keeley

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This is a fantastic thread! Terry it is always fun following your projects and the expert advice you get. Well done!!

And yes the 160C from the Nova break in is about right! I spent an hour in that booth watching with my own eyeballs! That motor was SMOKIN HOT!! The entire piston top to bottom (except for the very small seal area by the oil grooves) was absolutely pitch black (burned on castor). After the break in and test runs were done we let the motor cool for awhile before taking it off the test stand...he handed it to me and it was impossible to hold without a glove or doubled over rag! Every piece of metal on that motor would burn if it touched bare skin! We are used to getting the heads on our motors warm, but nothing like I saw there.
Keep up the good work!!
GQ

Wow, wonder why they run them that hot? Maybe they reach those temps in the cars? Maybe lower nitro than we normally run? You'd think they'd get piston galling at that temp?

Poking around I keep seeing around 250F from the airplane guys, many car guys too. Got a PM from Mike Rappold that said he normally saw 160 - 180F with his MAC 67 in a hydro.
 

GraysonTaylor

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I have a Hudy break in stand for car motors and the instructions say 200 to 250 F as a guideline. "Too cold or too rich will cuase premiture wear out." Only a guideline... Heat cycling is important to the process. Only slightly rich according to Hudy.
 

Terry Keeley

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I have a Hudy break in stand for car motors and the instructions say 200 to 250 F as a guideline. "Too cold or too rich will cuase premiture wear out." Only a guideline... Heat cycling is important to the process. Only slightly rich according to Hudy.

Cool little stand, small prop just like Nova Rossi's. HUDY

The Byron fan I'm using only turns up to about 20K, I'm gonna trim it down a bit next time out. I'd like to see mid 20's...

Not sure if I'd want baked on castor, do the car guys really run like this?






 
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David Murany

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Cool little stand, small prop just like Nova Rossi's. HUDY

The Byron fan I'm using only turns up to about 20K, I'm gonna trim it down a bit next time out. I'd like to see mid 20's...

Not sure if I'd want baked on castor, do the car guys really run like this?






They run about 20 percent castor when doing this. The fit is really good on the engines that are done this way. They last a very long time if taken care of.
 

Terry Keeley

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They run about 20 percent castor when doing this. The fit is really good on the engines that are done this way. They last a very long time if taken care of.

Must be the high castor/low nitro they run but they recommend 204-284F (95-140C) as a running temperature: Frequently Asked Questions | Novarossi World - NOVAROSSI WORLD

Why they would run them in at the factory at 320F (160C) is beyond me.

Got 1.5 gallons through this new piston/sleeve, coming in nicely.











Small chunk came out of the skirt already, man I wish they made them a little beefier there. Oh well, I'll be making my own billet units soon hopefully...
 

John Beardslee

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Terry from what I’ve heard NR only uses Alcohol and caster, no nitro.
Do you soften the edges of the piston skirt? I use cratex (rubberized abrasive) in a dremel.
 

Jim Allen

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Terry,

The pictures of your pistons look very strange! I have posted both brand new & used for many hours, pistons from pylon racing engines operating in the 29,000+ RPM range. The "wear band" (area where the piston rubs on the cylinder) is clearly visible on both new & used pistons. Notice the finish on the honed cylinder bores & the machined pistons. Engines made this way require very little break in time & their life at peak power is also greatly extended. The lubricant used in a pylon racing engine contains only castor oil.

Jim Allen

Note: Every sharp inside corner on the piston's inside bottom edges is broken with a cratex abrasive as John said.
 

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Terry Keeley

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Terry from what I’ve heard NR only uses Alcohol and caster, no nitro.
Do you soften the edges of the piston skirt? I use cratex (rubberized abrasive) in a dremel.

Isn't FAI fuel 80/20? Is that what they have to race with? Still can't understand why they want a baked on castor finish tho.

I usually round the bottom corners of the skirt but for got on this one, I think they can hit the crank web at BDC, looks like there's a mark there.


Terry,

The pictures of your pistons look very strange! I have posted both brand new & used for many hours, pistons from pylon racing engines operating in the 29,000+ RPM range. The "wear band" (area where the piston rubs on the cylinder) is clearly visible on both new & used pistons. Notice the finish on the honed cylinder bores & the machined pistons. Engines made this way require very little break in time & their life at peak power is also greatly extended. The lubricant used in a pylon racing engine contains only castor oil.

Jim Allen

Note: Every sharp inside the piston's inside bottom edges is broken with a cratex abrasive as John said.

How are they "strange"? Care to elaborate?

Found a pic on the MB site, this piston looks similar to your Nelsons.


What's a typical fuel mix for pylon racing?
 

Jim Allen

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Terry,

The Untitled Document under "running in" refers to the MB-40 FAI speed engine & what the piston should look like after running in is completed. The FAI speed fuel is still 80% alcohol, 20% castor oil as far as I know. This engine operates in the 31,000 to 33,000 RPM range. The reason the pistons in these engines are dark colored is because of the castor oil lubricant. Notice that the same type of "wear band" that is found on a Nelson 45 pylon racing engine pistons is found on the MB-40 FAI speed engines pistons. This "wear band" is the area where the piston is sealing against the cylinders wall. Notice that the remainder of the pistons circumference in both of these very high performance engines does not show any signs of rubbing. The fuel used in pylon racing engines is 15% nitro, 20% oil (could be some castor & some synthetic),65% alcohol.

Also notice in the Untitled Document photo of a broken in piston, the distance of the wear band in relation to the pistons crown. It is in approximately 2.5 mm (.099") which is the same as what is found on the Nelson pylon racing engine photos I have posted.

We believe this wear band is essential for very high RPM, HP type speed engines.

Jim allen
 

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LohringMiller

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Are you getting detonation? Our nitro pistons had holes and/or melted exhaust side edges.

Lohring Miller
 

Terry Keeley

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I think the difference between the CMB and the MB/Nelson piston wear patterns could be due to difference in material and also the taper used below the crown. I got some raw CMB castings years ago and had them analyzed, they had 18% Si. The RSA 431/444 used in the MB/Nelsons have 30% Si and a much lower CTE so the crown would expand less. The wear pattern on the CMB is "normal" from what I've seen over the years, with a wider band on the hot exhaust side and narrower band on the intake. The double band eventually blends into one on the intake side.

The dark color has to be higher running temps coupled with 20% castor. I've been running 15% oil (7% Morgan's synthetic/8% Blendzall castor) for break in. I cut back to 12% (8/4) once broken in.

Here's some more CMB pistons after break in:

VAC 45:




VAC 91:





VAC 91 (too lean too soon, usually happens on the exhaust side):


 
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Terry Keeley

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Are you getting detonation? Our nitro pistons had holes and/or melted exhaust side edges.

Lohring Miller

Not yet, still running fairly rich. Once broken in and working hard I usually get some frosting on the exhaust side of the piston and head.

If I lean too hard too soon I can get galling like the pic above, then it's another email to Stu, lol.
 
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Tony Ball

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Cool little stand, small prop just like Nova Rossi's. HUDY

The Byron fan I'm using only turns up to about 20K, I'm gonna trim it down a bit next time out. I'd like to see mid 20's...

Not sure if I'd want baked on castor, do the car guys really run like this?






Hi Terry
I've seen similar piston colour on the old OPS website.
Hope you don't mind but where did you find these pictures 🧐
 

Terry Keeley

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