NMPRA

This was probably the most informative discussion I have read.

Thanks all.

Good stuff guys. However, if I don't win the next contest I go to. I'm going to be pissed!

Thanks lee.

Stiff nose and fuel tanks..

The nose of the plane being as rigid as possible has a couple benifits. One, the motor is spinning at 28+ "or trying to" the vibration caused by the motor is harmful to the longevity of the piston/liner fit. Picture the piston traveling up and down, now, add a side to side vibration. The first thing it will do is kill rpm, the second it kill any possibe piston fit. If you used said airframe to breakin the motor, the motor never had a chance. Two, I also believe this additional vibration can cause the rod to fail prematurely.
Lee is a very smart @$$ modeler. I had an issue in PHX, ran it past him and got the answer immediately. The question was, the motors in one plane were bullets and in this airframe their burning up. He said the motor mount isn't tight and the blind nuts were the cause. I said I tightened them, he said "yeah against the mount". I pulled the now nogood nelson out and I'll be dammed. Blind nuts tightened against the mount. Pulled straight through the firewall from repeated tightening. He's the reason I use backplate rings. The beam mount should be anchored on the nose as well. A 6/32 sticking out half inch or more and some slow cure thickened up is what I use.

Fuel tanks and air leaks.

Take your favorite tank out of the plane, or, before you install it. Evacuate the bag. Now, plug the pressure line. Put the plunger half way on your favorite syringe. Hook it up to the fuel line on the tank. Submerge the tank in water. Push on the syringe. . If your tank is leaking you will find it here. This test should be done to EVERY tank you plan on using. If your chasing a ghost as to why it runs like crap this is also a good place to eliminate a cause.

great thread. Top Dawgs sharing Motor secrets. Good to see.

Let me clarify the leaky tank post. Basically, pressure test the tank prior to installing it. You don't need to push 50psi into it, push just enough to see if bubbles appear. 10 psi is more than enough. If you see bubbles, rebuild the tank and use fuel proof sealant to stop the leaks.

Fuel tanks and geometry.

Ideally you want the tank in line with the venturi. all 426 and 422 planes have the motors sideways or slightly downward. Which puts the venturi at the same angle. The tank should be mounted with the tank centerline inline with the centerline of the motor. Centrifugal force "going around the poles" causes fuel delivery to change depending on the location of the tank. A tank mounted above the centerline will have fuel forced into the motor causing a rich setting as a tank mounted below the centerline will experience a lean setting. The flatter the tank the more consistent the run. The jett flat tank is prolly the best choice for consistent runs as the tank has the least height of the commercially available tanks.

Fuel tanks and CG.

When possible you want to mount the middle of the tank "front to back" on the CG of the wing. This will keep the cg from changing as the fuel tank emptys during the flight and all 10 laps will be the same. Some tanks are difficult to mount fuel lines to the front on some airframes. Lots of FAI planes have the tank mounted fuel lines to the back. The design of some airframes have the widest point at the trailing edge of the wing. You will loose NOTHING by mounting the tank butt first and running the fuel lines up past it. If your hangup about mounting the tank backwards is the fuel line ID and restrictions, run the bigger ID lines.
If you have ever flown against Dr Roy and he handed you your arse, you got beat by a tank mounted backwards. There, feel better knowing someone who does it.

Ok Mr. Brown,
I had an engine running very strong. It dropped about 300 rpm. Probably ran hot.
If I understand your engine cleaning procedure, I would polish the piston with Mothers. A my mother is no longer with us, I will do it alone. When you say polish the piston, do you mean the top of the piston only, or do you polish the side of the piston as well?
The top is not peppered.
The head does have some black. Do you use the same polish for that?
As far as 1500 on the sleeve, you say oiled 1500. I assume you are talking about some castor or equivalent on the paper.
What do you use for overall cleaning and flushing?
Thank Ray, I mean Mr. Brown.

The sand paper I use to clean up the cylinder I cut a piece big enough to overlap it's self when it's opened up inside the cylinder. Using a finger inside the sandpaper roll the cylinder back and forth with the palm of your hand while moving the oiled up sandpaper in and out. The mothers is to clean up the piston. Don't polish to a mirror, just enough to make it look like new. this won't work on a piston that has lost it's fit. If there's no bite left you need a new piston. If there's still a pinch sometimes it can be salvaged. Remember you need to break it in again. I'll do a video and post it on here tomorrow.

Yes, you can clean the head with the mothers. Castor for assembly lube.

Ray
Where do you get your Backplate rings ??

Anybody have opinions on remote needles vs. venturi needle setups

H n M has them as does Adam argus.we should get dub and mike l to make them as well. If your handy you can make your own.I've made a couple from old beam mounts. Cut the beams off, drill and tap to match the bolt pattern, then drill s#!+ loads of lightning holes in it.

Aero Precision Machine makes the nut plate and an engine mount that I use which has five front hold down screws which mount to a G10 plate which in turn is all glued to the front of the fuse. Ask for the Von Der Hey mount. Von Der Hey.

Here are a couple of photos of the mount I use. Also a solid test stand is a good idea to have. Never ever peak an engine on the test stand just to see what it will do. You will hurt it. Adding an additional 10% castor oil to the fuel really helps with the break-in process as well. All of this is no secret it's just a lot of work. Von Der Hey.

Lee Vonderhay's test stand in nicer than my bedroom furniture.