P

pokey

Active Member
Gang
After flying the four for nineteen years it is time to update some things.

I want to put the long gear on it now. In searching the threads I didn't find much on this but perhaps someOne can chime in on this. I am guessing I will need a new engine mount in addition to the new gear legs?

Other parts needed would be new gear leg fairings, intersection fairings, and while I am at it new wheel fairings. All this will require new brake lines as well.

I am sure someone has already done this and would appreciate any ideas and consideration or concerns from all.

Thanks

Bill
 
gear legs available

I don't know how the change would go but I have a surplus set of RV9A main gear legs in the shop. They are new and "look to be taller" than what would be stock on a 4 . The 9A main legs are left over after purchasing a 9A project and converting it to a 9, these have never flown . If you need some dimensions let me know. I also have the weldment for those 9A main gear legs as surplus. I have them in cosmolene and wrapped haven't looked at them in couple years. [email protected]
 
A lot of work but not hard

I did this same exact mod about 3 years ago. It is not hard but involves a good bit of work. There is one mod you will have to do because the lower center holes on the mount will not match. I'll look to see if I still have the instructions from Van's. The rest of the mod is straight forward. It is not a cheap but it makes your -4 look like a real airplane vs a toy airplane and it may land a little better. I did it for looks and because I had a lot of grass stains on the prop and thought that was not a good thing.
 
RV4 Short to long gear

I rebuilt a very early wrecked RV4 which had a short landing gear & installed the new long legged gear. This aircraft had the engine pushed back into the firewall damaging the longerons that form the center console. Those center longerons had to be replaced along with a new firewall because of impact damage and not due to the landing gear conversion. I found the new motor mount was different than the old because the geometry of the new landing gear requires a different rake angle for the longer leg. The position of the wheels have to remain very similar due to design issues such as CG when on the ground. The two inboard motor mount bolts in the center of the mount are located slightly different due to this changed geometry meaning new pads have to be built for relocating these two bolts. Those pads reside just aft of the firewall inside the center console. In my case I also had to replace the lower corner MM bolt brackets as well due to damage so those holes may or may not have been relocated but I didn't care. I already had replaced that structure and I just drilled new holes to match the new motor mount. The old mount was heavily damaged preventing any real useful comparison to the new mount. This repair was easy because I had access with the firewall removed. You would have to replace those pads working from the cockpit which would be rather close working conditions but I am sure it can be done. This was written from memory of work done 6 years ago and is as complete as I can remember the situation.

Dick DeCramer
RV6 N500DD flying
RV8 Fuselage Slowbuild
Northfield, MN
 
Mount and legs

In response to your original question, the legs and mount definitely must be replaced together.

Other than "moving" the lower center bolt holes, the conversion is fairly straightforward. I did notice that the weld warpage on the new mount was significant, requiring some shimming to achieve a stress free fit.

Also, any time you mess with the engine installation, you can expect a little variation in the fit of the cowl, specifically with regard to how well the spinner centers on the nose ring of the cowl.

Aside from the improvement in prop clearance and handling qualities, the long legs really do improve the looks of the -4.

M
 
68" or 72" prop?

I did the change after I changed to a CS prop for proper clearance. The intersection fairings will not fit properly anymore. It was harder to land, and less visibility while taxiing. I definitely would not change unless you have a 72 inch prop installed on the plane. The shorter gear legs function perfectly unless you have installed a 72" prop.

Steve Barnes "The Builders Coach"
 
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