Throttle quadrant placement

[Pbruce]

I am planning dual throttles on my Patrol, connected by a rigid shaft and rod end bearings. The aft throttle is pictured. I mounted it outboard of the mounting tabs, which keeps the quadrant hurried inside the wall of the fuselage, rather than inside the cabin, protruding proud of the inner skin of the cabin. This is the arrangement shown on the plans.

As pictured, It’s neat, but I’m wondering if ergonomically it’s better to have the unit mounted inside the plane in order to leave more room for a fist between the throttle knob and the window pane.

One other consideration is that I will be mounting prop and mixture verniers on or under the left lower panel. It seems that burying the throttle quadrant in the cabin wall like it is in the picture keeps it clear of the verniers.

To anyone who has pondered this extensively, or sat in the plane lot, or better still, flown it with side throttles what do you recommend? Thanks

[joehmason]

While at Oshkosh in 2016 I sat in Mark Goldberg's old Patrol. It had the quadrants mounted on the inside part of the fuselage tubing (not under the window sill). When I pulled the flap handle up, one of the bolts on the quadrant took a nice chunk of skin out of my knuckle.

If you do mount underneath the sill, and the throttle is too close to the window for your liking, you could bend the arm slightly to help with clearance.

We mounted ours under the window sill so that it is flush behind the side panel. It seems like there is plenty of room, but you should build it however you think it will work best for you!

I do not think there is a wrong way to do it.

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[Pbruce]

That’s great! Thanks. I never considered the flap handle.

[Paul Johnston]

821928C7-D599-460F-A33D-88D3F2E710D2.jpgI have cable run outside fuselage tube

[spinningwrench]

I built a custom throttle quadrant for my Patrol to eliminate the flap interference issue. It sits between the outside fabric and the inside cabin skin. You can see the placement and cable routing here.

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[Bcone1381]

Try to run it outside like Joe, Paul and Bruce.

I ended up running mine on the inside. I've spent over a month build time with this issue. Knuckels and all. What I ended up with is good, simple, secure, fine in appearance clears the flap handle and I just shake my head at the time spent here.

Space issues that prevented running engine cables outboard due to how I installed the front left fuselage former. That dictates how much space you have outboard of the tubing to run your throttle cables. I wish I could move mine outboard another 1/2 inch. The inside vertical edge of MY front left fuselage former should have been centered on the T14 tube C-P tube (Plans p.17) I drilled it to run adjacent to the inside edge of the tube. I cheated myself of 7/16" of space.

Photos help me get ideas....my neighbor told me once "When you design from scratch its invention, when you copy someone else its called Research." hahah!!

Quadrants are mounted to the window sill aluminum with nutplates and 3/16" bolts.

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I can only fit one item here on the quadrant and maintain good clearance with the flap handle. I was able to keep my mixture and prop controls off the instrument panel and maintain good space when the flap handle is pulled. I don't give up panel real estate without a fight.

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I installed nut-plates in the quadrants face to recieve a screw to secure the cover. I wanted the cover easy to remove. It is.
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The headset jacks are mounted to non-conductive material (whats it called????? Phenolic sheet) on the bottom flange of the cover. The face down keeping all headset wiring down low. I think I'll like that.
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[rodsmith]

Well it turned out really nice Brooks, so time well spent. It is insane how long some tasks take, especially when you are designing as you go. I'm going through that now with my carbon fiber front doors.

[BravoGolf]

That looks great! Where did you source your prop and mixture cables?

[Bcone1381]

I used MacFarlane for the prop and mixture cables.

[Pbruce]

Very good information. Especially the bit about clearance from the former. Thanks

[Bcone1381]

Yeah!! That ended up being one a very small detail I was unaware of that dictated the future of other things.

[Pbruce]

Looks like the Avipro-supplied throttle lever located per the plans would put the cable right into the top steel mounting tab for the front aluminum former. Did anyone else encounter this? I’m assuming the easiest way around this is to drill another hole in the lever below the existing one to clear the mounting tab. It would be about 5/8” below the existing hole, and would reduce the throw of the throttle cable by about 25%, I’m guessing. If that is not enough to move the throttle through full range, I would have to move the attachment point in closer on the throttle as well. There would possibly be some minor increase in the amount of slop in the system. Not sure if this is an issue. Any comments? Thanks.

[Pbruce]

My system is looking identical to Joe Mason’s which I think is about as close to stock as one can get for a two-throttle step on a QB Patrol. Thanks to Brooks’ advice I am able to locate the cable outside the steel fuselage cage with no margin left. Whew.

However, I am unable to use the top hole on the throttle for the push-pull cable since it would punch directly through the mounting tab for the front former. (See image) I have to use the bottom hole on the throttle lever.

I’m becoming concerned about the meagre amount of cable movement generated by using the lower hole to connect the cable. It’s only 1”. The top hole provides 1 7/16” but as I said, I can’t use it because of the interference issue with the mounting tab for the former.

Has anyone used these throttles? Most importantly, Has anyone used the lower hole for the cable and did it work? I’m really concerned about continuing on my current trajectory with this if it isn’t going to work well. Thanks again.

[joehmason]

Pbruce,

We did encounter this same issue. We notched the bottom of the metal tab in question to allow room for the throttle cable to run forward using the top hole in the quadrant arm. There was still plenty of room for a rivet to hold the former in place.

As you also described, the issue with moving the cable to a lower hole on the quadrant arm is that it reduces the throw of the cable. Even in the top hole of the quadrant arm, the movement was insufficient to get full throw on the carburetor throttle arm. After lots of research I reached out to Aerosport Power, who built our engine. They told me it was acceptable to drill a hole in the arm of the carburetor closer to the rotation point. We did a lot of math and figured out where we needed to drill, then went in another .030 to make sure we didn't overshoot it. We can now hit both stops on the carburetor arm and the quadrant arm is within 1/8" of the front and rear stops.

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[Pbruce]

Ok thanks for that. I wish that there was sufficient material available on the tab to allow grinding the bottom for enough clearance. I don’t think it will work, but I’ll have another try at it. Thanks for the pic of the carb throttle arm. I don’t suppose you have a picture of the penetration of the front former with the push-pull assembly in place?
Thanks.

[Pbruce]

I think I got ‘er! I filed the bottoms of the mounting holes in the bracket holding the throttle quadrant so the quadrant will sit a little lower. (1/16” maybe). I then ground away the bottom half of the offending former mounting tab, up to the outer edge of the old rivet hole. I anchored the front former to the remains of the tab with one 3/32 CS steel pull rivet. I have just over 1/8” margin of steel around it. I riveted an aluminum doubler/scarf connecting the front window frame to the lower former to stiffen the top of the former as best I could.

Thanks again to Joe for assistance, also Brooks, Bruce, and others.

For anyone coming behind me in their build, I would measure against a throttle quadrant, and if required, weld 1/2” of steel sheet onto the top of that tab at the earliest opportunity. Also, REALLY watch the tolerances between the bolt-heads holding the quadrant on and the fabric exterior of the plane. I had none to spare, but as long as I substitute countersunk screws for AN3 bolts, I’m able to keep the mounting hardware clear of the external fabric. Just. Read Bcone’s post above. Consider putting an extra outward- bowed stringer in that area, and if that doesn’t do it, cover with aluminum if required to I sure fabric doesn’t run on throttle quadrant bolts. Call upon me for clarification any time.

Thanks to all for assistance.

[Bcone1381]

Pbruce sees what I did not see until later in the build. Look at the head of my red arrow. I (and I assume Pbruce) stopped the left lower stringer here, at the aft fuselage former which coexists with the D-N fuselage tube. Just above my Red Arrow is a segmented line on the plans showing that stringer extending further forward to the C-P station. Thats my Blue line.


Now I've covered the fuselage, the fabric is shrunk, and the green line shows a bow. The fabric panel below the window bows out slightly at the front and rear of the panel due to the shape of the formers. But in my installation the center of the fabic bows in slightly (the green line) due to the straight shape of the top window sill and bottom longeron. I should have exteded the former all the way to the C-P point

I've got no issues the clearances. My fabric is not rubbing on anything, but its closer to stuff than it needs to be and I suspect a slight appearance issue when its done.

I'm moving forward, next time I'll try to extend that stringer forward to the former at the C-P tube.

So here is a tip for you all to consider as you build. We will get better and better as we all go along, helping each other.






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