Coolant hose too close to Exhaust Pipes - Rotax ch750

Coolant hoses have burned through twice because the radiator on the ROTAX 912 ULS width makes the hoses very close to the exhaust pipes.

I need a guarantee fix that I can fly with a peaceful feeling knowing that the radiator/hoses won't shift over the 1/4-3/8 " space and burn through again.

I have ceramic coated the exhaust pipes to insulate the heat. I was told to put high temp hose oversize over the 1" black hose but that would also eat up space.

Really need an answer here to get back in the air.

ANYBODY ELSE OUT THERE HAVE THIS PROBLEM?

Sent an email with photos to Roger at Zenith. Hope to hear from him soon.

T

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Replies to This Discussion

Permalink Reply by James R Depfer Sr. on June 26, 2014 at 5:25pm

Ralph,

Could you post those photos here too, so we can see if your routing is like ours that haven't burned through (yet!) ?

Jim

Permalink Reply by Tracy Buttles on June 26, 2014 at 9:19pm

im working on a fix for that right know , ill try to get some pics out

 I have bent the exhaust tubes as far as I can and I made some heat shields

 and on the left side im making a standoff bracket to hold the hose away

Permalink Reply by Christopher Jon Brown on June 28, 2014 at 12:09am

Heres what I did, hope it works! Added exhaust wrap to the exhaust pipe and put thermoshield wrap self adhesive around water pipe and used stainless zip tie.  They touch now but seem soft and pliable and hoping for the best. I only have 8.8 hours on the plane so far.  All I smell when I return from a flight is the fiberglass getting hot.

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Permalink Reply by James R Depfer Sr. on June 28, 2014 at 11:08am

Christopher,

I'll have to double check mine again, but on you number 1 photo on the passenger side is where, I'm pretty sure I have plenty clearance, and I think my oil line is closer to the exhaust pipe, with the coolant line slightly below and behind the oil line. I have fire-sleeve on the oil lines. I don't see any fire-sleeve on you lines. Did I miss that, or are you going without fire-sleeve ?

I forgot to ask before.... Are your parts from the Zenith firewall kit, and did you route your lines using the video ???

Jim

Permalink Reply by Christopher Jon Brown on June 28, 2014 at 12:14am

Heres the other side. Again hope it works.

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Permalink Reply by Ralph Gregus on June 29, 2014 at 2:21pm


Trying to send some photos that shows some areas of close tolerances. I need a better photo angle of the right side from the top...this is now the worst spot. I tried that aluminum insul wrap on hoses; it burns through when touching the exhaust pipe. Hopefully that exhaust pipe wrap will help. I want to see airspace between to carry off heat. I have ceramic coated exhaust pipes to cool heat emission. My mechanic friend made an aluminum pipe section but still needs a short hose to attach to rad and that is the closet spot...so no good.

I know some builders have used a larger diameter high temp hose and wrapped it around the black hose, then tying back. I am afraid that it will also touch and burn.

I am thinking now of acquiring 1" high temp hose and with SS tie straps positively tie both sides away from pipes to allow for some airspace. Then, a third rad bracket to engine on the left side top to inhibit the rad from moving side to side.

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Permalink Reply by Ralph Gregus on June 29, 2014 at 2:24pm

More photos...

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Permalink Reply by Ralph Gregus on June 29, 2014 at 2:26pm

2 more pics...

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Permalink Reply by James R Depfer Sr. on June 29, 2014 at 7:09pm

Here is a  photo I just looked at from Bob McDonald's photos. As you can see the hose closest to the exhaust pipe is wrapped with fire-sleeve, and is tie wrapped.  I believe some fire-sleeve is good until about 2000 degrees, but you should verify that. I don't think Bob has any problems that I know of, and the Rotax install video was taken during his engine install. There are a couple of other photos on Bob's member page that shows the engine and hoses. If you look at the photo full screen, and then blow it up you can see the connection at the front end pretty well too.

http://www.zenith.aero/photo/ch750-rotax-912s-install-2/next?contex...

Permalink Reply by Jan van 't Schip on June 30, 2014 at 6:26pm

Hi Ralph,

I think most heat transmitted from the exhaust to the cooling hose is radiant heat. Also the coefficient of emission of ceramics is about 4 times higher than that of steel, so the radiation is even more. I would put a heat shield in between, made of aluminum. Aluminum has a high coefficient of reflection. If the heat shield is double wall, you could even ventilate air in between.

Aluminum, shear and bending brake are in my barn and you know where to find the place. Please let me know if you need anything.

Regards,

Jan van 't Schip

Permalink Reply by Ralph Gregus on July 1, 2014 at 12:46pm

The problem that has occurred for me is when the black coolant hose has come into contact with the exhaust pipe. After it happened on the left side I re-securred hoses on both sides. However, things(hoses, rad?) moved around while flying, probably from excessive vibration, and the hose on the right side was able to touch. It burned through the aluminum heat sleeve I obtained from an auto speed shop. So...lesson here is, "Don't let the hose touch the pipe".

Also, I want to contain the movement and provide as much airspace as possible between. As can be seen in Bob McDonald's photos: he only added a layer of red high-temp hose covering the black hose and it looks like vinyl ties were used. There are NO photos showing the space between pipe and red hose. Bob had NO PROBLEMS. I think that as long as there is space for airflow, and protect hose with high temp hose (I plan to replace the black hose with high temp hose, SS ties) should be good to go...The Jet-Hot application 2500 has aluminum in it. It should provide a cooler under cowl temp and more efficient engine running. As for emissive character, I don't know. But I think the less temperature close to the High Temp hose should prove the answer for me. MUST KEEP HOSE FROM TOUCHING AT ALL COSTS. Trying to add metal between (no room) would add metal heat sink and transfer to hose. YIKES. WEAR PARACHUTE. Ha. Just want to fix it and get back to flying. Been grounded by this and my back surgery. Getting both plane and body healthy and into the air where man belongs.

Permalink Reply by Walt Snyder on July 1, 2014 at 3:31pm

Ralph,

I put stainless steel zip ties on my fire sleeve where close to the exhaust only because I've had issues in the past with heat and UV light on zip ties, there are some that can become brittle over time. 

Walt Snyder

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