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Min/max toe-in specification?

R

roee

Well Known Member
Does anyone know the specifications for min/max toe-in for the -7A main gear?

I looked and could not find this in the plans nor in the builder's manual. I know the topic of toe-in has also come up on the forum before, but in searching here too I couldn't find a definitive specification.

I plan to call Van's on Tue to find out straight from the source. But I don't want to hold up progress for the remainder of the long weekend, so I figured I'd ask here in the mean time. Someone must have asked Van's that same question in the past.

Thanks!
-Roee

P.S. FYI- I measured 1.3 degrees toe-in on the left main, 0.0 on the right. Hoping this is within acceptable tolerances, but if not, I'd prefer to find out ASAP since I'm now working on the fairings.
 
It's baked in to the pre-drilled gear legs and mounts and seems to be very well done at the factory. You shouldn't have to worry about it.

Jim Sharkey
RV-6 - no leg dampeners needed
 
Hard numbers, please

Jim, I appreciate your enthusiasm, but that's actually not all that helpful, and I believe not entirely true. Evidently, there is a fair amount of measurable variation in how closely the factory drills the mounts and legs. Variation in toe-in could substantially affect ground handling and tire wear. And reading through anecdotal reports in past threads, it seems that these problems are in fact not uncommon.

Some variation is acceptable, and must be. I'm trying to ascertain how much variation is too much. In other words, what are the tolerance limits. This is a question Van's engineering should be able to answer. I was just hoping someone here might already know.

Now, this topic has all the potential for becoming another one of those unending debates. I don't want to go there. I'm just looking for the hard numbers, if someone's got them.

Thanks,
-Roee
 
Roee,
Are you checking landing gear tor in/camber with weight on or off the plane. I am wanting to do the same on my old RV-6A that appears to have the tops of the legs spot welded in the sockets.

Thanks
 
Gear Legs

Our RV6 1992 vintage kit gear legs were drilled incorrectly.
We had significant handling problems and accelerated tire wear.
The recommended fix was to clamp a beam to both axles.
We then drilled the retaining bolts oversize. This resolved the wear issues and handling problems.
I will look to see if I retained any specifications at the Hangar later today.
 
Alschief said:
Our RV6 1992 vintage kit gear legs were drilled incorrectly.
We had significant handling problems and accelerated tire wear.
The recommended fix was to clamp a beam to both axles.
We then drilled the retaining bolts oversize. This resolved the wear issues and handling problems.
I will look to see if I retained any specifications at the Hangar later today.
Click to expand...

Thanks Al. Were you able to find the specs?

So it sounds like it's 0.0 nominally (that's what the beam would achieve), but still wonder about min/max tolerances.

P.S. what were your toe-in angles before you corrected it?

Thanks,
-Roee
 
Axle Alignment

I did not ascertain the Degree of error. The drawings show an 8'6" distance.
Center to Center. No tolerance is shown. I can testify that the tire wear is now minimal and the ground handling is much improved. Vans will have to provide the needed information. Vans also suggested the use of the beam
to get the zero alignment.
 
If you want to get it as close to perfect as you can, you want to set the toe-in/out to zero with the airframe on the ground, tail down if it's a taildragger, with weight on the wings to simulate fuel and a pilot. The gear legs bow and you want to set the toe in the configuration and weight that you'll be taking off and landing. The Rocket guys use grease plates under the tires to allow the gear to "squirm". We then drill the sockets to the legs. I know the RV's are a little different but the idea is to get it as close to zero as possible.
 
jsharkey said:
It's baked in to the pre-drilled gear legs and mounts and seems to be very well done at the factory. You shouldn't have to worry about it.
Click to expand...

My 9A was originally this way and I had significant wear on the left tire and the gear leg angle with the ground was different. Although it could have been how I installed the gear tower (also predrilled), I'm not convinced that the problem wasn't how the leg was drilled at the factory, or how the tower was welded up. When I went to TD configuration, I aligned and drilled the holes myself. Not enough time on it yet to see whether there are wear issues, but I'm hoping it is straighter this time.

greg
 
The word from Van's

Spoke with Gus at Van's. He stated that they don't have a min/max tolerance specification for toe-in in particular, but that the tolerance on the bend in the gear leg at the factory is +/- 1.5 deg, which depending on direction can translate to that much variation in toe or camber, and they haven't found this to be a problem.

He also noted, and this makes sense to me, that with the free-castoring tri-gear configuration, the effective toe-in is essentially the sum toe-in of both mains divided evenly between them, even if their individual toe-in with respect to the fuselage is asymmetric. So with my L:1.3, R:0.0, I effectively have 0.65/0.65 toe-in on an airplane that rolls on the gear at 0.65 degrees to the right of its longitudinal axis.

He also indicated that in terms of handling characteristics, slight toe-in is generally preferred over toe-out, due to its convergent (self-correcting) properties.

And finally, the deflection of the gear with weight on it tends to produce a slight toe-out change (can't quantify "slight"), so that will compensate some in my favor, or at least not make it worse.

So, bottom line is according to Van's my toe-in measurements are typical and should not produce any significant adverse effects. I'm still slightly uneasy with that (admittedly I have perfectionist tendencies), but more uneasy with the alternative of trying to rotate and re-drill the leg and socket for over-sized hardware. So at this point I'm going to just go with it. If, once the airplane is complete and flying I find that it's causing problems, then it'll be a more extensive project to fix it after the fact, but do-able. So be it.
 
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