SJN

What am I doing wrong ?

This is my second header that has gone bust on me within 10-15 flights.

The only things I can come up with is: Im not balancing my APC props, or I heard someone say that the pipe has to "hang" in its CG.

What do you think ?

The engine feels like a sewing machine when at full throttle.

How do you detect an unbalanced prop ? Does the plane shake or something ?

SJN

mean time solution.......its just not the same.....

bob27s

My Feedback: (19)

Wow... that bites.....

Typically, you should leave about 3/16 to 1/4" of gap between the header and the pipe inside of the coupling. That usually avoids pipe-hang vibration loads.

Clamping the pipe futher forward will help as well. Try to move the clamp up around the weld seam. As you noted, mounting closer to the CG of the pipe will limit the inlet end travel due to any vibrations.

Rudeboy

SJ,

Replace the crappy 2 piece engine mount that comes in the box with a sturdy one piece unit like in the pictures.

My header cracked rather fast too, and I concluded that it was because the stock engine mount is just way too flexible. I soldered it up with Techno Weld, and replaced the engine mount... and my resoldered header held up fine for quite a while after that.
It was just impossible to keep the engine tight on the stock mount.

With engines like these you need sturdy mounting... or something WILL give... sooner or later...

Other than that... balance your stuff to the limit... a magnetic balancer is a real asset... you won't believe how far off balance your stuff really is until you put it on a magnetic balancer...

der_steuermann

My Feedback: (2)

Yes, APC props usually are unbalanced - in fact almost no prop comes properly balanced from the factory []

IMHO, we should balance all props and spinners regardless of brand and application (even for a 4-stroker). Just eliminate potential dangers best possible...

SJN

Thanks guys..... my pipe and header were stuck right up against each other.

Ill take my header with me to work and see if we have something that can weld in this stuff...

LGM Graphix

My Feedback: (22)

With absolutely no disrespect intended, in all my years of running pipes, 3/16" to 1/4" is not a good idea at all. 1/16" is the maximum I run for 2 reasons. 1, the silicone coupler lasts longer, and 2, when you leave to big a gap, the tubing actually pulsates, this can and typically will not allow the engine to properly come up on pipe.
The vast majority of my experience with pipes is on the YS61AR's and OS91 VRDF's. The 91's have no silicone coupler, they mount totally differently, but even on my Nelson F1 engines you wanted next to no silicone tubing exposed. I have never had my header crack on my V1, and that includes a couple less than perfect incidents that damaged the rest of the plane. The only thing I can really suggest is make sure the mating surfaces for the engine/header are dead flat, and that the header isn't hitting the fuse. I had to cut my magnum fuse down to clear the header. Also make sure the bolts really are tight, I have found on the V1 headers the tapped threads will bottom out before the header is actually completely tight.

bob27s

My Feedback: (19)

Jeremy,

You are absolutely correct......the tigher the gap, the better .. especially when it comes to coupling life and system performance...... expecially in extreamly high performance applications. However, you never want the metal to touch metal when using a coupling.

Jett FIRE engines typically utilize o-ring type engine couplings, and for the most part we use welded pipe/header assemblies. Solves most of the problems.

On most of my pattern engines back in the higher rpm days of the 80's, I typically use to leave 1/8 to 3/16 of a gap. When using a vibration isolator mount, I would leave about 1/4" gap to accomodate the engine deflections.

My post was intended to address the cracked header from a sport/performance point of view. From my experience, failures such as these tend to be caused by a high frequency vibration which is excited by some undetermined engine RPM. By insuring there was about a 3/16" gap between tubes, the coupling will function a bit like a vibration dampner and help change the natural frequency of that hanging exhaust system. The exhaust temperatures and pressures developed by the engine are reasonable enough where that exposure should not rapidly cause a coupling failure. Clamping the pipe in a different location will also change the natural frequency of the installation.

As you noted, hitting the fuselage would cause a problem too.... from his photos it didnt look like that was an issue.... hard to see though.

The only times I have personally experienced a problem with cracked headers was with .61 RE pattern engines (OPS 61 in particular). Those repeated failures were traced to exhaust temperatures and temp cycling which caused metal/weld failures over time. Only ever experienced it with the OPS too.... something with the way the cylinder/exhaust cooled had to do with it.

Clearly, there are other ways to address this, and other possible causes for the problem.

LGM Graphix

My Feedback: (22)

Bob,
I see where you are coming from, I do know from my experience with the West 50VI's though that having to much of a gap causes the engine to quit or run lean. I had this problem on mine until I got my pipe nearly touching the header. There were 2 other people that posted about problems on here somewhere of the engine quitting and I suggested closing up that gap and the engines ran great after that as well.
When you use a soft mount I agree you want a slightly bigger gap, however, on all my pattern engines I made sure the pipe was soft mounted as well and never had any problems. I actually started making teflon couplers so they wouldn't burn out. This made the pipe to header fit very rigid, but with both engine and pipe soft mounted it was ok. Same when I went to the 4 strokes.

The West 50VI header is an odd header in the way it slopes down right after the mounting block, the biggest problem I've experienced with these headers is the threaded holes not being deep enough. It will snug the header to the engine, and the bolts will be totally tight, but it won't be tight together. The bolts are actually bottoming out in the header. I always retap my holes now so that I know they will seat tight.
I also use 5 minute epoxy for a gasket, basically it all squeezes out only filliing the smalles gaps, this allows for a very secure fit from engine to header.

SJN

Thanks guys.

Its probably because I had no gap at all that my header cracked. How on earth should I know that you have to have a gap
Doesn`t say anything about it in the manual. My header isn`t touching the fuselage. No trimming was nessecary on the Magnum R. On the old Magnum I had to trim the fuse.

Can I fix these headers somehow ?

Can they be welded or soldered with mig/tig/silver solder or smothing ?

I might even have some extremly high temp metal-epoxy at work,that might do the job. How hot do you think the header can reach ?

Rudeboy

Epoxy...? Don't even think about it...
Forget about MIG welding too... you'll end up with a big hole... MIG welding alu of less than 2mm is extremely difficult...

TIG welding would be you best option... providing you can find a welder good enough to get the job done AND providing you get your parts clean... There will be oil in the aluminium sufaces of the crack, and that is very difficult to get out without residue. For TIG welding fast oxydising metals like aluminium you ABSOLUTELY need clean materials! Even clean new aluminium plate welds better when you brush it off with a stainless brush first...

Last option is using some sort of aluminium solder... not as strong as a real weld though, but relativily stout... and easy enough to work with...

If you can't get 'em fixed... send 'em to me... I could use 'em...