Building a rotisserie

[Allen B]

Hello, thanks in advance for any info.

I have a model 5 QBK coming soon and I’m in the process of building the rotisserie. I have a few questions I was hoping to get answered.

1) How tall about the ground would be adequate to allow for full rotation?
2) What am I missing about using U-Joints? My rotisserie is perfectly level and the posts are perfectly plumb to the floor. Are people using U Joints to prevent torque on the frame? Is this really an issue if it’s level and plumb? It seems like if the center of rotation is the same on both ends this isn’t necessary. Even if it’s off by a degree or so I can’t imagine there being that much torque on the frame.

please, any feedback would be appreciated.

Thanks
Allen

[TJ_Slice]

I used U-joints on mine. I think you would have some binding if it weren't exactly aligned.

Also, it seems like it would be difficult to get the fuselage in the rotisserie. It would at least require multiple people. With the u-joints, you can mount one end while the other is still on the ground. It's and easy job for 2 people.

These are the U-joints I used, I am sure you could find a cheaper alternative: https://www.amazon.com/dp/B07DJ715JS...d_asin_title_1

[Alaskanf1]

Getting the rotisseries plumb and level would be the easy part. The hard part would be getting a post off each end of the plane that is perfectly true with the center of rotation that you choose. You would have to pull a string line through the fuselage to get the posts set perfectly. The U-joints make it so all of that is not nearly so critical. It also allows you to make easy adjustments if the initial placement of your posts didn't provide a balanced fuselage (you can adjust the height of one end without having to adjust the angle of the other). And as TJ_Slice mentions, you can have one end sitting on the ground while you get it mounted. U-joints are cheap, just buy two and it will save you many hours of frustration.

[Allen B]

This is why I love the forum lol. I would’ve never had the foresight to think about the issues with mounting the fuselage. I can see how having one end resting on supports would make the mounting job a million times easier. Thanks for the advice.

I’ve read other builders have a total height above the ground to the center of rotation of around 44-48”. Any thoughts on that being an accurate height (at least to get started). I plan on making the posts adjustable in height to be more precise but I’m just looking for a place to start.

Allen

[Allen B]

TJ. Did you just use the pre drilled holes in the U Joints and bolt it onto the rotisserie? Or did you end up welding something? I’ve seen some larger U Joint brackets with 3/8” attachment holes. I have to imagine that should suffice but I’d like to know what everyone else is doing. Thanks

[Bcone1381]

My rotissorie has no u-joints. I would not build one with them, but would not refuse one that had them. ( an example https://bogertaviation.com/collectio...ete-w-o-wheels )

LIke you say, just ensure each rotissory point is at the same height and align each end to point at each other. They align to make an imaginary axle. When the fuselage is attached I aligned the two points using a string and the legs of the rotisserie base pointing at each other. Then You can keep watch of that alignment. It is not hard to keep it aligned.

Build it so the two bases float a bit...build a bit of slop (like 1/4") lets them self align, or lean a bit. You'll want to connect both rotisserie bases to each other if you are going to move it around the shop. Lifting the rotissory up onto dollys can help make if jive and dance and introduce "give" to the alignment.

Regarding how high should the rotisserie points be.....Your fuselage has a center of gravity that is three dimensional. Most of us only are use to visualizing the longitudinal CG. You will discover that It has a vertical CG as well and will pendulum if the vertical CG is not on the axle. So consider building an adjustable weight box onto your fixtures or inside your fusealge or on the firewall to adjust the vertical CG. I had a wood firewall and built a fixture to hold a 40 pound John Deere Suitecase weight. It was a bit too heavey and pedulumed my fuselage right side up. I had to rotate the fuselage and pin it hold it in other positions.....that was fine.

Back to Rotisserie point height....The top of the Vetical Stab must clear the Rotisserie base by an inch or more. So it depends on how its mounted. (the mounting points is another good topic) Position the tailwheel spring receptacle below the rear rotisserie point. So when the fuselage is rotated the top of the vertical stab was my low point and it had to clear that base leg.

[Alaskanf1]

Here are some pictures from my visit to Bearhawk this last summer, might give you some ideas.

[Bcone1381]

That is the most significant rotisserie I've ever seen. wow.

[Allen B]

That’s a sweet rotisserie. I’m shocked that they only connected the front with 1 steel bar and the back with a single attachment point as well. Thanks

[huntaero]

I did a post in Rotisserie a while back check it out

Rotisserie - Bearhawk Forums

[U2fletch]

I did the Harbor Freight engine mount routine. Welded on the u joints. Having the mounting point on the tail adjustable is no joke. As construction progresses, the CG will change and it’s nice to adjust the centerline to keep things neutral. An engine hoist is invaluable to assist in getting the fuselage in and out of the rotisserie. My wife thought I was silly buying a hoist from Tractor Supply instead of borrowing one from a neighbor. She admits now that the hoist has proved itself to be useful in so many unanticipated ways.

20250927_151711_resized_1.jpg 20250403_173224_resized.jpg

[Allen B]

Thanks everyone for the feedback. I think I’ll weld on some U Joints if for no other reason than the ease to attach and remove the fuselage. I’ll be working solo on this a lot and it sounds like a little extra work now might be worth it later.

[spinningwrench]

Rotisserie.jpg
This is my simple jig with an indexer built from a gear, has worked well all the way through paint.
Rotating Mechanism.jpg

[alaskabearhawk]

I think I have four videos about my rotisserie on YouTube. This is one where I mention balancing the weight as it rotates around the axis so it turns easily:

https://youtu.be/Pi4PRpJSVLc?si=h9DjO8o6YyRgW-gI

[RatherBFlying]

I did not use any U-joints. I just aligned center of rotation front and back and it works well. Keep in mind every hour you spend working on your rotisserie is an hour your not making progress on the airplane. Rotisseries are nice, and can make you more efficient at building, but it's possible to build a plane without one. I've heard of people just bolting 2x4's to the engine mount holes in a tic-tac-toe shape so they can rotate the fusulage in roughly 45 degree increments and use a saw horse on the tail end. Kind of rough but gets the job done. I did feel building a rotisserie was worth while, and have enjoyed having one, but kept it simple / quick to build.