Twitchy handling on rollout

[F1R]

WHAT diameter are the main legs at the gear sockets in the engine mount?

Any chance you can have a machine shop mill the holes in the gear legs oversize to 5/8 or 3/4" and then press in solid shaft, then clean up turn the ends the same dia as the gear leg. You would have a clean leg to put holes in with zero toe in.

[dnh98221]

I have a -3B and it’s a total pussycat. I’ve run the tire pressure from the mid 20s to 50 psi and see no difference. Full flaps stabilized on final at 70 knots, I probably flair about 55-60. Since you have a lot of high performance tailwheel time, I suspect it’s not you. My plane is based just over the hill (Cascades) at Skagit, BVS; looks like about 200 nm. If you want to come over and to some side by side comparisons, you’d be most welcome.

PM me if you wish.

Dan

[Cloudboy]

I'm home sick so I've had time to continue researching my handling problem. I've found 3 friends who have flown RV-3's and all report them stable and easy to handle on rollout. They are probably better pilots than I am, but still, none reported any problem. I measured the toe in of the main gear. The left main is toed in 1/8th inch or .72 degrees. The right main is toed in 3/8 inch or 2.15 degrees. The building instructions state be careful to get the gear straight when match drilling the leg to the socket because it is difficult to fix. That appears to be an understatement. There is no ability to shim to the correct angle.
The mothership referred me to Harmon Lang, who builds the gear legs. Mr. Lang suggested I remove the legs and check them for straightness first. He is able to straighten bent legs. He also suggested I could drill the holes oversize up to 3/8 inch if it would correct the misalignment. The plans are inconsistent about the diameter of the hole to be drilled, some places 5/16 is specified and others 3/8. Until I can get to the hanger, I don't know what I have. Mr. Lang was very specific about not welding on the gear legs to fill and redrill the holes.
The bushing suggestion is good but a machinist suggested I may be more difficult than it appears to ensure adequate wall thickness for the full diameter of the bushing after redrilling.
A very good welder said he could fill in the holes in the socket for redrilling. He was concerned, however, that the welding would affect the id of the socket and prevent gear leg insertion without reaming.
As soon as I can take things apart I'll have a better idea how to proceed. The instructions appear to be accurate, misalignment is difficult to correct. If all else fails, new gear legs ight be necessary.

[rvaitor87]

I've been flying my -3 for 10 years now, and I've had no problem with the toe in. I've found that a lot of times if I land straight, I don't have to touch the pedals for the entire rollout. Of course, I don't always land straight so this is not an all the time occurrence. Also when I was doing my transition training with Jan, that the -6 seemed hard to land, and control on rollout. Every RV is different in the way that they handle, so I would suggest that you find what works best for you.

[jrs14855]

Perhaps the easiest fix is to have the gear legs annealed, reinstall them, heat the bend red hot and reset the toe. After they cool of recheck. Remove the gear legs and send them to Harmon for reheat treat.
The alternative method requires eventual removal of the mount. Also requires a TIG welder and an operator who can weld in tight places. Suspend the airplane with a hoist with straps around the upper mount tubes. Elongate the mount holes until the toe is where you want it. Fabricate some washers at least 1/8 thick from 4130 flat or 4130 tubing, just large enough to cover the holes. With the gear legs clamped at the axles very lightly tack weld the washers in place. One tack weld, let the weld cool, then the next tack weld.
It is almost certain that the engine and mount will need to be removed to finish welding all around the washers.
Both methods have been used successfully on Wittman Tailwinds. I favor the first method.
Obviously it would be best to purge all fuel from the system before welding/or bending the gear. The round spring gear was designed and patented around 1950 by Steve Wittman. He called for 1/16" toe in measured in the length of the axle. When the airplane is loaded this likely becomes zero toe.

[F1R]

I agree with the bending adjustment solution idea.

One more idea.. Not knowing how much length of straight socket and shaft are available, try and achieve the desired alignment with the through bolts removed while suspended as described above. Perhaps there is space and a location in the gear socket to allow a new hole to be drilled & reamed . No heat treating and no welding required.

[Cloudboy]

Here is an update on my gear leg adventures. I took the wheels, brakes, etc. off the legs and checked alignment against a heavy steel I beam. There was some toe in with the gear hanging in the air. With wheels on the ground the toe in was lessoned, as Mel said. I was able to take the suspended toe in out, reassemble and test taxi. The plane behaved better but still I tended to overcontrol. I disconnected the tail wheel steering and handling was even better. I may remove the one sided arm and put the original chains and springs back on with some slack. But they are so ugly. Tail Lynx are no longer available. The best option may be simple cables with slack and no springs. We'll see.
Thanks for all the input.

[fixnflyguy]

I've been watching your post, and not sure what direction your headed (no pun intended ), and it reminds me of a -4 I flew from Fla to NC for a friend. I have a -4 I built, and it handles like a dream..at least to me, with the non-full swivel old school OEM tailwheel. While doing the walk-around of the subject -4 I ferried to NC, I noticed lopsided tailwheel tire wear, and a "rocket link" on one side as many have chosen to switch to. Taxiing was more difficult than mine, and the departure roll for take off made me wonder if I should abort. I was following a Cirrus home (had had ADSB) and figured I just had a crosswind biting me a bit. Stopped for fuel and did a 3 point as I usually do..JEEZ..left/right/left..ugh,near disaster.Take off from there I lifted the tail ASAP, and performed another horrible 3 point back at home field. I have 700 plus TW hours, and this one worried me. The previous owned never flew off pavement, so he didn't have complaints about it. the new owner in NC had zilch TW time, and while he was doing his training (in a different plane) , we reworked the stinger holes and squared up the tailwheel, replaced the tire and ditched the rocket link. All is well and good now !

[Cloudboy]

Bill
Thanks for your experience with the Rocket link. It confirms my belief that it is too direct a link. Lots of people swear by them and say they get better control. Me, I overcontrol. I'm going to have some sort of hookup to the tailwheel so I don't have to use brakes all the time to steer on the ramp but I will have plenty of slack in the cables.

[Cloudboy]

Good news, the twitchiness is resolved. First I aligned the gear straight ahead by the method in the plans. Then I reinstalled a two sided control arm for the rudder with slack chains. The plane still turns quickly but it is far more stable.
It's no longer scary on rollout.