Scale Wendell Hostetler 30% Piper Cherokee Glass Fuselage Build.

Making the anti-servo control rod. Here is the full scale rod. The rod is 1/2" in diameter. Here's a short video of how it works.


Turned a KS 3/16" x .049 wall tube down to .150" diameter and aluminum brazed the mounting pad using Harris 1070 al-Braze filler and Al-Braze EC flux. Used a propane torch to slowly heat the aluminum until the flux turns clear liquid at this point the filler is just about ready to melt, a little more heat and it flows into gap. The filler was placed in the flux before heating. The filler melts about 50 degrees below the aluminum so caution is needed while heating or it just turns into a blob. The 3/16" x .049 tube can be tapped for 4-40 without drilling

brazing an alloy with propane seems intense. I'll have to save this info!

The stabilator tab hinging is completed. Now onto the control linkage.

The spiral diaphragm kit arrived. Comes with new diaphragm, level and setting gauge, the gauge drives the cost up, you can buy the kit without the gauge. Unlike other Walbro carbs, the lever is set .055" above gasket surface. Look closely on the bottom of the gauge under the WALBRO is the surface used to set the lever height. All I need now is a carb to put it in!

Completed the anti-servo tab control linkage. Used DuBro heavy duty rod ends, the connecting link is 3/32" G10 because that's what I had on hand. The upper link is K&S 3/16" x .049 aluminum tube tapped 4-40 and screwed into a 4-40 Tee nut with a 3/8" large washer to spread the load. Here's a short video of the operation.

Smooth operation there.

I must say it works better than I had hoped.
Did a little work on the engine. The intake had 1 10.25 mm throat, the new carb has 1/2" bore (13mm).
Ordered 1/2' ball end mill to open the throat to 1/2",took longer to set up the piece on center than to do the mill work. Should have taken a before photo as there was nasty step at the bottom of the bore, the ball end mill removed it nicely. Thinking about making an adapter plate so that the carburetor shaft is horizontal so that the primary fuel holes staddle the centerline rather than favor one side of the intake. Been reading a post about the FG57 that proceeded the 61 and there were a few post about rich and lean cylinders, not much info about the 61. I did see one fly and talked with the owner and he was happy with it so I went with that recommendation.

The genuine Walbro WT 962 carb arrived, since it was purchased as a replacement for a RCGF engine it already has airplane style control arms. Put the spiral diaphragm kit in it, checked the pop off pressure, 28 psig release, 18 psig reset, good to go. Ordered material from McMaster Carr to finish the installation. Both the intake manifold and the carburetor have heat isolators so I plan to make new to accommodate the longer heat isolator. Things have been busy here so not much work was accomplished recently.

Need to get the cowl ready to mold. The oval below the engine centerline where the headlamp is located was off to the left side by 1/8", cut it free and moved it over to the center According to Aircraft Spruce the 140 has a 12" diameter spinner, 30% of 12 is 3.6" 3 1/2" is close enough. The plans show a 3" spinner. Glued a 3 1/2" diameter 3/32" thick piece of aircraft plywood on and filling and sanding smooth. There seems to be many variations of the cowl nose bowl based on photos. Would like to have the cowl to mount the engine so that I can install the firewall.

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TonyHallo said:

Making the anti-servo control rod. Here is the full scale rod. The rod is 1/2" in diameter. Here's a short video of how it works.
View attachment 123268

Turned a KS 3/16" x .049 wall tube down to .150" diameter and aluminum brazed the mounting pad using Harris 1070 al-Braze filler and Al-Braze EC flux. Used a propane torch to slowly heat the aluminum until the flux turns clear liquid at this point the filler is just about ready to melt, a little more heat and it flows into gap. The filler was placed in the flux before heating. The filler melts about 50 degrees below the aluminum so caution is needed while heating or it just turns into a blob. The 3/16" x .049 tube can be tapped for 4-40 without drilling

View attachment 123270

View attachment 123269

Click to expand...

Thanks that was informative