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-   -   Sniffle Valve, Throttle cable, and Fuel Flow Xducr (https://vansairforce.net/community/showthread.php?t=122849)

rzbill 02-17-2015 03:09 PM

I used a brass 45 street ell on the sniffle valve. Gives good clearance on my M1B. Short hose and aluminum pipe to the cowl exit as has been already said.

My throttle cable is the same as yours, with fire sleeve and no shield but I bent the bracket to get all the clearance possible (nesting the cable up towards the sump). No cable damage so far due to this close proximity (350 hrs). However, I would put a bit of sleeve over the blue rubber bushing. They will dry out, crack and fall off without it.

Quote:

Originally Posted by Danny King (Post 959994)
What you have done with the throttle cable will not work! At normal cruise speed there will be enough airflow to keep the throttle cable from melting, but at low speed the fire sleeve will act just like an oven, and will not save the cable from melting around the inter cable. It will freeze in place when it cools.

Danny, he has used the bracketry and exhaust provided by Vans for the M1B. Its not custom work. They do call for a heat shield there but there is no room. When building, I initially agreed with your assessment and watched this area closely during phase 1 (and still do). I'm not sure why our experiences have been so different.

Danny King 02-17-2015 07:03 PM

Throttle Cable
 
Quote:

Originally Posted by rzbill (Post 960198)
I used a brass 45 street ell on the sniffle valve. Gives good clearance on my M1B. Short hose and aluminum pipe to the cowl exit as has been already said.

My throttle cable is the same as yours, with fire sleeve and no shield but I bent the bracket to get all the clearance possible (nesting the cable up towards the sump). No cable damage so far due to this close proximity (350 hrs). However, I would put a bit of sleeve over the blue rubber bushing. They will dry out, crack and fall off without it.



Danny, he has used the bracketry and exhaust provided by Vans for the M1B. Its not custom work. They do call for a heat shield there but there is no room. When building, I initially agreed with your assessment and watched this area closely during phase 1 (and still do). I'm not sure why our experiences have been so different.

My problem appeared many hours after the first flight. In-fact, it happened as I explained in my example flying into Oshkosh. Others have had the same thing happen. I'm sure you can fine other examples in the archives. I believe it was Iron Flight that mentioned a company that can make custom cables that are of aircraft quality, and can handle much higher temps. They are expensive, but might be worth it in this case. If you are forced to fly slow for an extended period of time, you may very well suffer the same fate. You are totally grounded until the cable is replaced. In my case, I removed the cowling in front of Home builders headquarters and put maximum force on the servo lever while a friend put maximum force on the cockpit mixture lever and suddenly the cable broke free. It was very stiff, but I was able to limp it home. I fixed the problem by installing Van's mixture bell crank moving the mixture cable away from the exhaust. Over time, my throttle cable became stiff and had to be replaced, and it had a metal shield.

This is a recurring problem with many RVs. Another fix would be to make a bracket that holds the cable further aft from its present position and use an extended threaded nut to make up the distance to the throttle lever.

I hope you never encounter this problem, but looking at the picture of the installed throttle cable, I can't see how it would be different.

BillL 02-17-2015 07:39 PM

Is it worth considering . . . .
 
Is it worth considering - moving the exhaust pipe down 1/2"? That looks too close to be the exact design intention.

hydroguy2 02-17-2015 09:36 PM

no sniffle for me, always use the Purge valve to shutdown,so no fuel available to leak.
my throttle cable is further from the exhaust than yours and started getting stiff at 100hrs, so added a heat shield. Still working (290hrs), but not as smooth as originally installed.
originally has the red cube in your location, tried wrapping it like you. I had stumbling issues at idle when landing that we tracked to boiling fuel. Still had trouble after trying rerouting, more firesleeve, etc. finally moved the cube behind the firewall installed between the boost pump and mechanical pump....stumble problem solved.

sent you a PM about sniffle valve

TCONROY 02-18-2015 12:47 PM

Solutions...
 
Here are some solutions:
1. Sniffle Valve too close to exhaust:
I spoke with Don at AirFlow Performance and ordered a 45-street elbow and his sniffle valve. From what I can tell, this should be a great solution to get the rubber hose/aluminum tubing away from the exhaust.


2. Throttle cable too close to exhaust:
I have to give Adam Burch(sp?) credit for the solution to my throttle cable problem. I happened to ran across a page in his builder log which is exactly what I needed! I simply removed the bracket and rotated it so the throttle cable is moved about 1.5-2" to the right of the engine. I also had to increase the bend in the bracket as it was hitting the bottom of the engine with the new orientation. Previously the firesleeve was touching the exhaust, now there is more than enough room to install a heatshield with a 1.75" gap between it and the firesleeve.






3. Fuel Flow Transducer
I found a 1-1/4" long 1/4-20 bolt to go all the way through the snorkel and provide a shank to bolt an adel clamp to on the backside of the fuel servo. I installed the flow transducer and secured temporarily so I could determine where the output fuel line needs to be shortened where it screws into the flow divider on top of the engine. Marked the fuel line and send to Tom at TS Flightlines.




Sure appreciate everyone's input! I'd have to scratch my head a whole lot more without Doug providing this great forum!


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