Problems with Wittmann Gear Installation

Hello everybody,

okay - it's not about an Vans RV but about my Ultimate Biplane, which uses the same gear as the RV-series.

Main problem was, that someone (either the previous owner or the factory) installed the inner tubes of the gear leg tubes wrong - the short ones with 1.5" are installes on the lower end, the longer ones with 3" are installed on the upper end where the bolt runs through. I'm just in the process of milling out the welds and removing the old tubes. Just cut the 1 1/2"*.058 tube as per plans to length. Did a test whether it will fit over the gear legs (OD 1 3/8") and unfortunately it will fit - with a little play.

Is this the wrong diameter? Isn't it correct that the tubeing has to be reamed in order to accept the gear legs? If so, I'd have to order som 1 1/2"*.083 tube and ream it to fit afterwards.

Unfortunately I can't tell how it was done on my RV-3 ; but it definitely looks as it has been reamed.

Am I right with the assumption that I need some tubing with smaller inner diameter?

Thank you in advance for the support!

Simon

On RV's that use the rod style gear legs, the sockets are honed to size in the engine mount or gear leg mounts after all welding has been completed.

Gear

1 1/2" x .065 inserts. measure the od of the gear and have the id of the tubes machined to a snug fit before welding in place. Since you will only be edge welding the bottom of the socket tubes there should be minimal distortion.
Most of the Tailwind builders are welding a short bushing across the bottom of the socket and slotting the socket and bushing with a die grinder. AN5 bolt thru the slotted bushing. Tighten the bolt after final installation of gear.
Depending on the clearance you might get away with just the slotted bushing without replacing the inner tube.

Gear

You got the spelling almost right but only one n, as in Wittman Airport. Steve Wittman invented the flat spring gear in 1935, the round gear a few years later.

Thank you guys for the replies! And the correction - Wittman with only one "n". Got it.

Problem is that the 1 1/2*.058 tube is a loose fit one the gear legs, it rattles around on the legs if I put it on them to test fit it. Reaming won't be necessary because it won't be too tight. Therefore I'm asking: Tubes too small or not?

1 1/2*.058 should have an ID of 1.370". The gear legs are a little below 1.370 unfortunately, my first guess was wrong. Will try to link a video of it, one second.

Sorry for double posting. Please find my video below:

https://youtu.be/BuLhB9u57eY

Thanks plans state .058 tube, but as jrs14855 stated .065 will be the correct fit. Guess it's about the 20th mistake I find in those plans...

Thank you all, will keep you posted as soon as the new tube arrives. Just finished removing the old tubes.

Finally the new bushings are in and reamed to fit the gear legs perfectly.

Now I'm struggling with the alignment. Does anyone know how to set up the gear the correct way? I know that 0 camber and 0 toe in or out are the goal, but how to get there? From my currect status: Gear legs already drilled, outer tube drilled but not correct (previous owner) inner tubes without hole.

Are those gear legs and engine mounts drilled to fit together off the factory? Who manufactured the gear legs marked with "AAA"? Thank you for every tip or hint!

https://imgur.com/a/DtN8Ra8

Cheers, Simon

Gear

Wittman Tailwind uses 1/16 toe in and 3/16 camber measured reference the length of the axle. The gear as installed on most biplanes does not have the swept back angle that most installations have. You may want to check in on the biplane forum for better info on your installation. The goal should be to achieve slight camber at the load condition where you will be most of the time. Biplane forum is www.biplaneforum.com