Throttle Quadrant

The early Monocoupes had a really neat throttle quadrant.  For some reason, not many survived over the years and many seem to have been replaced with traditional push-pull cables. I’m not sure which models had these. I’ve seen them in the Model 90’s and Model 110’s, but I’m not sure if they were used in the Model 90A’s. If you know the answer, please send me an e-mail.

 

Of course, my project didn’t have one. About 10 years ago, Ron Wenzel, then owner of the Kinner ‘Coupe, had 10 throttle quadrant housings custom machined out of billet aluminum. These were sold by the Monocoupe Club. I bought one and it is pictured above along with two examples of original quadrants.  As you can see, these came out great.

 

Now the challenge is to recreate the inner workings. Once again, Norman Cowell comes to the rescue. His NC533W has the original throttle quadrant and he sent me a drawing of the levers. Norman said the levers look like little Loch Ness Monsters and he’s right!

 

 

 

 

A long time ago, I was able to stick my camera up behind the instrument panel of N18629 in the museum at Oakland, and take a picture of the throttle lever—to—bell crank– to cable mechanism.  The big cable on the left is the throttle cable. On the right hand side you can see the carb heat cable and the mixture cable.

 

 

Norman was able to take this picture along with the unit in his Model 110 and decipher it and came up with the drawing to the left. The bell crank mechanism translates the rotational motion of the levers into push-pull motion. The bell cranks are connected to the levers via links.

 

 

I made some levers using MOH (Material On Hand) just to confirm geometry and dimensions.  With just some minor tweaking I came up with a final pattern that works with my housing.  The levers rotate on a 3/8” OD shaft and connect through links to a bellcrank assembly which translates the rotational motion of the levers into sufficient push-pull motion to appropriately move the engine controls.

I did quite a bit of prototyping of bellcranks, etc. until I came up with final shapes and dimensions. Used Autocad to draw up the bellcranks.

 

 

 

 

 

Layed everything out on a sheet of 0.125” 4130 steel. Pre-drilled the holes just because it is easier to clamp the entire sheet in the drill press rather than individual pieces. Then cut everything out on the band saw and cleaned it up with the sander.

 

 

I fit this along with the prototype panel into the fuselage to verify the clearance between the throttle bellcrank bellcrank assembly and the firewall and determine how I will route and clamp the throttle, mixture and carb heat cables.

More pictures in the gallery.