Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

BROKEN MANIFOLD

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Old 08-24-2009, 02:52 PM
  #1  
thundertiger76
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Default BROKEN MANIFOLD

I have a MagnumR with West Eurotech 50V1 engine, Genesis tuned pipe
and manifold.

After about its 10th flight the manifold broke in half while in the air. Westonuk sent me on another but guess what, the same thing happened.

It seems the manifold is too thin and not enough weld around it.

What can i do?
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Old 08-24-2009, 03:16 PM
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mk1spitfire
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Default RE: BROKEN MANIFOLD

I would call weston again and again
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Old 08-24-2009, 03:20 PM
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Default RE: BROKEN MANIFOLD

Im sure Mike had a cracked weld too?
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Old 08-24-2009, 06:22 PM
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Default RE: BROKEN MANIFOLD


ORIGINAL: thundertiger76

I have a MagnumR with West Eurotech 50V1 engine, Genesis tuned pipe
and manifold.

After about its 10th flight the manifold broke in half while in the air. Westonuk sent me on another but guess what, the same thing happened.

It seems the manifold is too thin and not enough weld around it.

What can i do?

The header to flange connection seems to be laser welded or ?? - but there is nothing much in the way of a fillet of metal there. I don't think that connection likes vibration much, under even moderate loads. I think the pipe needs to be well anchored and keep the supporting loads on the header to a minimum. I really do not know if this is a systemic problem or a few isoloated cases, but their process hasn't changed that I can see.

I flew my Magnum many times without issue. I then installed the engine package on a Screamin Demon, changing to a nitro pipe with half the weight of the Genesis pipe, BUT no proper midpipe support. I only had the outlet stinger clamped to an Al bracket, although firmly. The header broke in a few flights. I ordered a new one and anchored the pipe to relieve the header of the loads, so far so good but the long range prognosis is not available yet.

How is your pipe anchored? Are your props well balanced and all that, how's the vibration level?

MJD


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Old 08-24-2009, 07:34 PM
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Default RE: BROKEN MANIFOLD

Does this pipe have a weld fillet that looks like a stack of dimes that got knocked over? If so, that is heliarc welding and it will be prone to cracking in that application. If the weld looks more like a smooth concave fillet with no ripples, that is what should be hydrogen gas welded and it wont crack in the weld, but maybe off to one side if the material is too thin. Even tiny scratches in the metal during the prep work can and will form cracks.
I asked a guy at Mac's about their success / failure rate and he said in the beginning they didn't have the process done pat. It took a little time to achieve near perfection, but they got it right now. It is amazing work they do.
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Old 08-24-2009, 09:25 PM
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Default RE: BROKEN MANIFOLD

Hi CP - it looks like this. What form of welding is this? I see no added metal, or so I think, I could be daft.

TT - is yours made in the same manner?

On this one, I clamped the stinger as before, that standoff is made from .030 aluminum and secures it well but certainly does not damp any vibes whatsoever, more than likely aggravates them. The central bit is a standard pipe mount bracket with tiewrap. On this pipe, there is no cylindrical midsection, so the tiewrap generates a bit of rearward push as it clamps. That is fine though - the rear standoff together with this hold it firm and steady. Now, the silicone coupler is simply plumbing, not structural anymore. I think that will make the difference, unless the header is capable of failing with nothing attached to it. The pipe inlet and header line up pretty closely btw, and are mebbe .080 apart, a bit less than what Ed recommended but no fretting or contact indicated yet. I hope it works anyhow.

With the Genesis pipe things are easier since it is a muffled pipe and has lots of cylindrical real estate to clamp to. It's a heavy pipe though, and it would drive my Demon's already rearward CG over the brink. That's the main reason I.. well, no, let's be honest. It's the main excuse that I use for substituting the open pipe for it. The main reason is that it sounds really snotty and scares people, and should have more peak power if set up right.

MJD

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Old 08-24-2009, 10:52 PM
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Default RE: BROKEN MANIFOLD

MJD, it appears to be gas welded. Some RC car pipes are the only ones where I've seen heliarc [TIG] work. A TIG bead is a big deposit.
Does the pipe carry through the flange, or is it butt welded? IIRC, MAC's pipes carry through the flange, or at least into the flange against a machined shoulder..

The gas welding process is tricky because the thick flange needs to be brought up to temp before the tubing, then the tubing will almost be ready to collapse as the filler rod is added. If everything is perfectly controlled, you see very neat work like you show there.
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Old 08-25-2009, 12:49 AM
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Default RE: BROKEN MANIFOLD

Before anyone thinks Weston UK has any role in the failure of this header, let me assure you they do not..

Here before you is the grim result of a pipe suspended on one end by a .50 wailling at about 21k while screwed to an airframe that dampens vibration about as effectively as the head of a snare drum, and on the other end by a sheet aluminum standoff screwed to glassed balsa wing sheeting on that same airplane. "How to make two parts hammer themselves to death - Part I" as written by moi.

It's much better now. Oh and see the pipe? It's a fatigue failure around and on the boundary of the weld as far as I can see. I have a pic of the flange somewhere, can't find the flange itself now..

MJD

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Old 08-25-2009, 01:46 AM
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Default RE: BROKEN MANIFOLD

that header was either laser or ultrasonicly welded, mac's uses straight acetylene torch heat for headers such as they sell, from your pictures. MJD, i see two things, the silicone connector is hitting the wing, and your pipe clamp wasnt isolated, we usually slip a silicone hose over the stinger then use a standoff, i prefer suspending pipe by its midsection or largest diameter, the weston header has quality control issues, as the seam/bead junction is porous from over heating during weld....and the result is extreme brittleness, i have broken some mac's headers, only by violent impacts with this planet[>:][:@] that header end where it meets the pipe has seen some serious fretting and impact, you busting perma frost???with it?[8D]
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Old 08-25-2009, 09:29 AM
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Default RE: BROKEN MANIFOLD


ORIGINAL: lfinney

that header was either laser or ultrasonicly welded, mac's uses straight acetylene torch heat for headers such as they sell, from your pictures. MJD, i see two things, the silicone connector is hitting the wing, and your pipe clamp wasnt isolated, we usually slip a silicone hose over the stinger then use a standoff, i prefer suspending pipe by its midsection or largest diameter, the weston header has quality control issues, as the seam/bead junction is porous from over heating during weld....and the result is extreme brittleness, i have broken some mac's headers, only by violent impacts with this planet[>:][:@] that header end where it meets the pipe has seen some serious fretting and impact, you busting perma frost???with it?[8D]
No, all survivable landings.. that's merely the result of several flights of end to end hammering from vibration alone. [:-]

The new install seems to work though. I could open up the stinger clamp and put some rubber in there, or make a new one. The West header drops a little bit from exhaust level, and yeah the coupler is grazing the wing, but I don't think there is any mayhem going on there. I'll keep an eye on it. The main thing is that I can remove the coupler, and the header and pipe are lined up and locked in their respective places and separated by a reasonable gap.

MJD



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Old 08-25-2009, 12:01 PM
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Default RE: BROKEN MANIFOLD

Hi,

I took a couple of pics today of the first manifold that broke on its own and some of the second which are still attached to my plane.

Looks very similer to MDJ's pictures.

I do balance the props and i also left about a 4mm gap between the manifold and the tuned pipe to try and eliminate vibration.

I know some one who had a similar problem and they made a manifold out of copper, more flexible.

I spoke to Westonuk today and they were very good with helping me out. They said that they would make a different manifold altogether and that it would be baked in an oven for hardness, should get it for the weekend.

Cheers, Craig (thundertiger76)
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Old 08-25-2009, 03:15 PM
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Default RE: BROKEN MANIFOLD

Good to hear they are helping you out.

As noted above, pipe mounting is very important. Most headers are not designed to take any sort of load on them.
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Old 08-25-2009, 03:23 PM
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Default RE: BROKEN MANIFOLD

I learnt that a small gap between the pipe and manifold is better than touching as you end up with a mushroom pipe entry. The gap I guess helps take away vibration between them.
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Old 08-25-2009, 05:18 PM
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Default RE: BROKEN MANIFOLD

by suspending your pipe in the middle , you affect the resonance or vibe frequency i have seen the stingers on boats break, by being solid mounted rater than soft mount, mac's bakes their parts at 400 F for eight hours after all other processes, to restore near t6 temper, so weston is going to do it now as well........doh
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Old 08-25-2009, 06:08 PM
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Default RE: BROKEN MANIFOLD

So would a support on the back side of the hump be the best for rpm, too? I wonder if a pad of high temp silicone caulk about 1/8" thick would work?

On a similar note, I've seen rpm jump by grabbing an engine by the upper cylinder with a pair of channel locks. It was impressive enough to make me consider making a clamp off the firewall.
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Old 08-25-2009, 07:52 PM
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Default RE: BROKEN MANIFOLD


ORIGINAL: lfinney

by suspending your pipe in the middle , you affect the resonance or vibe frequency i have seen the stingers on boats break, by being solid mounted rater than soft mount, mac's bakes their parts at 400 F for eight hours after all other processes, to restore near t6 temper, so weston is going to do it now as well........doh
Maybe they already do heat treat their parts after welding, but the guy who calibrates their lab oven is the same guy who calibrates their radar gun.

MJD
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Old 08-25-2009, 08:14 PM
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Default RE: BROKEN MANIFOLD

That means he thinks the oven is doing 400, but it's really only doing 350.
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