Grove gear geometry question

[lostman 198]

Now that I have had some time flying and working on the "new" plane, I am realizing just how far splayed out the grove gear is on both sides and more noticeably on the pilots side.

 

John told me that Robbie Grove told him to just stick it back in a press to change the geometry after he had a "rough landing" (whatever that meant). I can do that but I'm really needing to know to what point I should re-bend the gear?

 

Here is what I'm thinking. From the measurements I've taken on the angles it appears that the right side gear is slightly bend at the lower bend, as compared to the other side. The larger upper section is at the same angle once the fuse is leveled from side to side. Pointing back to just the lower radius not having the same bend.

 

Does anyone know what the camber angle was on their grove gear when installed or what it should optimally be?

 

Mine has about 3" degrees of camber on the pilot gear and about 1 degree on the passenger side. Both are leaning with the top of the tire/wheel combo inward. I know from the older taildraggers I've flown that most have an opposite camber built in but need to know what to rework this gear to so that it's at least closer than it is. I don't want to wear out just the insides of the tires and also know that too much camber can make for some crazy ground handling. I'm pretty sure that the difference in camber right now makes the plane load side to side just slightly when landing on pavement, but I'm more concerned about not wearing tires and trying to eliminate the torsion created on the axles since they are already bend slightly, which in my mind could lead to more since the leverage changes quickly with more angle.

 

I've already emailed Grove about this but haven't heard back yet. I couldn't find anything on their website stating geometry either.

[Av8r3400 1179]

I had a bent Grove spring that I was going to straighten and use on the Mangy Fox.  I decided to get a new spring that was taller instead.  But, the engineer I spoke with at Grove told me that anything more than a "slight bending" will require re-heat treatment of the spring to keep the strength of the aluminum.  Which means sending it back to them for forming and heat treatment.  Time and $$.  It was only slightly more to get a new spring at the taller dimensions I wanted anyway.

 

IMO, the optimum situation would be zero camber at rest, at gross weight.

 

Your notes were a bit confusing, did you mean 3" of negative camber or 3º of negative camber?  3" is quite a bit, more than what I would consider to be "slight".

[lostman 198]

The 3" was a total typo. It was meant to be 3 degrees. What they consider to be "slight" might be less than what I would consider to be slight. I think rebending the gear by 3 degrees wouldn't be too much but they might disagree with me.

 

I'm really wondering why they would use the treated aluminum if they are bending it and then having the reheat it? The properties of aluminum are such that if they do they might has well have started with something not treated and then worked it to a treated state....at least that's my take on it from what I understand. I didn't realize they were having to heat treat it at all after the shaping had taken place.

 

I can't understand why it would only have been a little more to buy new than to have a current gear leg reworked. Especially since they just raised their price about $500 on the gear in the past month, at least from what I remember it being when I looked at it in January for the Avid gear. I may be mistaken but I'm pretty sure it was only (cough cough) $1,700 for the Avid gear before. When I looked today it was over $2,200. That's a pretty big jump if it's the case. Not to mention that my gear are custom made and have the gun drilled brake line through the center of them and that's another $200 to bump the price.

 

I may just end up putting shims between the axles and gear to remedy the situation if I can't bend the gear straight.

 

I think you're correct with the no camber at max gross, but I was hoping to get somewhere in the ball park before bending, loading the plane, checking etc. That is if there is any way to bend it to that point in the first place.

[Av8r3400 1179]

I would tend to agree with the idea that 3º of bend should be doable.  I had already straightened and twisted my gear (what I considered as an engineer) quite a bit - several inches at the axle mount point.  I was not concerned about having it re-heat treated, itself.  But, I was a little concerned about the strength if I used the extensions that I was going to build to raise the front of the plane.  I decided that the cost was worth it for the longer gear.  I think it was going to cost me near $1000 to send the gear to them to be heat treated, plus time and material to further bend the spring, then send it back.  I still needed wheels, axles and brakes, yet.  So-- long story short, for a few hundred more I got a new spring to my specs and sold the old spring for nearly the difference.

 

The alloy that these springs are made from (forgive me I don't remember - I think 7000 series?) is a heat treatable alloy.   It gains it's final strength from heat treating.

 

The blank is first cut to length, the gun drilling is done, then it is forged to the required shape, the spring is heat treated, final machining is done of the brake ports and axle mounts, it's sanded and then shipped.

[lostman 198]

Thanks for the information. I think I'm going to try the shims first since a guy that works with my wife has a full machine shop in his basement and basically said to come "play". He does stuff for free for his friends just to see what he can go. It's the easiest route for now. Besides I don't have a way to support the entire aircraft while I pull a gear leg off right now. I saw the post the other day on jacking the aircraft and the tripod that someone had (can't remember who it was) and I really like that idea, I just don't need another thing to carry around with me when I move, which is always just an inevitability with me. Not to mention I would have to redo the brakes when I pulled the gear since my gear is the brake line. Shims are just going to be quicker for now, but I'd rather have it right in the long run.

 

Any guesses at to if a 20 ton press would to the bending I need?

[Av8r3400 1179]

I did most of my bending with a 6' piece of pipe and a lot of grunting.

[EDMO 1078]

Some Grove info -

Kenneth,

      When the Pursang was made, Grove, I think, was still using 2024 material - the heat treating after bending is also to relieve stress and make sure it retains its shape.

      Current Grove gear is now made with 7075 material, because it can be made a little lighter, and heat treatment is done in batches of gears to lower cost of treating.

If you send them an old, 2024 gear to straighten and bend, then the cost goes higher, since it has to be treated separately as the treatment (temperature/times?) is different than the 7075 aluminum.  A new gear leg might be about the same price?

      I have talked to Robby Grove about this in the past.  Grove also makes shims for the gear.

     Somehow, you have to get a medium point on your camber so you have the least tire wear at the weight you normally fly your plane.  

Kitfox owners in the past have reversed their tires at every condition inspection to even out the wear on them.  

      If you are landing mostly on concrete, you will find that the outside of the tires wear more from initial touchdown until full weight is on them, if you have set them at zero camber with weight on the gear, because the gear will spring down when not under load.

EDMO

Edited 26 Mar 2014 by Ed In Missouri

[lostman 198]

Ed, I wish that my problem was the tires touching on the outside so they would wear enough so that I could turn them around. As it is they don't even ride in the center of the tire when the plane is unloaded, thus the inquiry about the geometry. If you look back at some of the first pictures in the Pursang thread you can see how it was sitting, that was without fuel and nothing in the plane. Now that it has fuel in it all the time it's much worse. Probably 2 degrees, just a guess.

 

Larry, How in the world did you bent your gear with a 6' piece of pipe? I guess you're another person on the forum I don't want to arm wrestle with!

[Av8r3400 1179]

One of these helps, too...

 

 

The spring wouldn't fit in the press.  Too awkward...

[lostman 198]

That and a 6' pipe, I can see it now!!! I guess there is a huge advantage to having two piece mains. I'm pretty sure I can get mine into a press fairly easy.

[EDMO 1078]

John made the Pursang with 2-piece gear so he could change it out or fix it easier in the bush - It shouldn't be too hard to jack / block it up and take off one side.

EDMO

Edited 27 Mar 2014 by Ed In Missouri

[lostman 198]

Ed,

 

You are correct about him making it that way for the ease of change. However, to take the gear off requires that you rebleed that side brake as well as figuring out how to block/jack the aircraft up. Something I'm not sure I'd be able to do if I messed it up in the back country. He told me the only time he had to straighten the gear up he was able to fly it home. Not sure what happened but it even tweaked the carry through area enough that I'm almost wondering if that is where the geometry issue is coming from.

[EDMO 1078]

There is a good article in Kitplanes mag this month on gear alignment.

EDMO

[lostman 198]

That would be great if I was a subscriber. Seems you have to have a subscription to read it. It's not that I don't know how to do it, but it would be nice to see what they are saying in the latest news about it. I've heard everything from setting toe in to toe to no toe at all. I'm not sure what to buy into anymore.

 

With the latest change of the tailwheel to the Matco 6" that I already had the rudder and steering on the ground in much better. The problem I'm having now is the resonance the tailwheel creates that wasn't there with the Maule, every crack across the runway is exaggerated through the airframe like a tuning fork. Not sure what is making it do this yet. The issue is that I also re-arched the spring at the same time so it could be there instead of the tailwheel itself. I just know that the Matco is much louder than the Maule, but the Maule was getting worn out in the oilite bushing and it was easier to replace it that replace the bearing since I already had the other assembly. I really wonder if there is something I did when I bend the spring in the press, like the top spring isn't sitting solidly against the lower one causing the reverberation. Just  thought. But it does steer so much better that I'm planning on keeping it and troubleshooting the noise.

 

I flew the plane again for a few minutes today and found that the flaps will hold at least up to almost full, but it was so bumpy I didn't stay up for very long. I need to get up again and check it out if I can ever get some smooth air. It's tough here in the mid-west this spring to find good weather. Hope everyone else is finally leaving winter behind.

[EDMO 1078]

Kenneth,

        The article was good in telling how to check your alignment.   As far as the age-old toe-in-out question, they had the same thing that I have read a thousand times:  some say toe-in / some say toe-out / some say no-toe at all...........   I need to read it again, but think the article went more with no-toe.....

EDMO

Edited 29 Mar 2014 by Ed In Missouri

[EDMO 1078]

I can recommend "Kitplanes" mag for everyone

- In this months issue, the wheel alignment article, 3 guys building a Bearhawk, the cowl insulation article, and the stick grips articles,  and , building a WW1 replica, and a gyro article, not to mention the electrical section, DAR section, and Barnaby Wainfain writing about aileron flutter.

      Far more than you get from "Snort Aviation" and reading about some woman taking a ride in a Super-duper $500K factory-built, or writing Kitfox articles by mis-quoting what Ed Downs wrote years ago.

 

You can get 10 issues and a book on "getting started with Kit Aircraft", for $15.95 - but make sure you don't get screwed by one of the false addresses who try to sell the mag illegally.   P.O. BOX 8536, Big Sandy, TX 75755-9842 is the real address.

<www.kitplanes.com>

Didn't mean to steal the gear thread - but if you had Kitplanes, you could read about aligning gear.

And, NO - I am not on commission - just passing the word.

EDMO

Edited 29 Mar 2014 by Ed In Missouri

[SuberAvid 617]

Kenneth,

 

Are both the Maul and Matco TW's that you have solid rubber?  The solid rubber ones are louder than the pnumatics.

 

BTW, I think Kitplanes mag is the best but still I get Sport Aviation and Flying as well.  Those magazines dream about flying big $$$$ though, so are mostly useless to me other than an occasional interesting article.  Flying to clueless when it comes to experimental aviation.

[lostman 198]

They are both solid, which is why I really want to swap out for a larger air type tire. I've come to the conclusion I can build my own fork for the Matco and buy a 4" wheel and tube/tire to make it all work. It's the lowest money outlay to get to a dual fork 8" that way. I think I even have a good solid bike that is 4130 I can cut up for the fork part. Just need to pull the tailwheel apart for a day to get it done. Oh yeah, and buy a 4" wheel and tube/tire combo. Matco wants $46 for just the wheel but I'm pretty sure an Asuzalite for half the price would work really well. I have three of them but they are in Utah and on my ultralight so they don't do me any good right now.

 

Anyone have an old jazzy style wheelchair? I know they have the correct 8" wheel/tire on them. My dad uses one on his ultralight and it's a really well built unit. They don't skimp on them when it's on a high dollar wheel chair from what I've seen.

[EDMO 1078]

I can post the business card with the $15.95 Kitplanes magazine offer if anyone wants to copy and mail it in.

EDMO