Bush gear differences

[TJay 1041]

is there much differences between avid bush gear, Highwings bush gear and kitfox bush gear which ones do you guys like best

[C5Engineer 1170]

Dimension wise they are similar. Not sure about wall thickness between the three. The Highwing uses a little bit different Cabane angle on their V. The metal die springs they all use have almost zero travel. Some have converted them to bungee. Leni used some snomo springs and lengthened the travel and I am going to try the TK1 racing cabanes with 4 shocks.

[akflyer 1427]

I will be testing the 325 pound per inch springs today.

[High Country 69]

I'm building a custom wide gear very similar to the Avid bush gear only im using cub style bungees and making it a little wider than the airdale gear. I'm building them for both the Avids and Kitfox. Main tubing is 1" .058 4130. If you are buying one made for the other keep in mind that the cabane will be different. Kitfox had one width and avid had two different widths. FWIW but any of them will be much better than any of the stock gears out there. 

 

-Robert- 

 

Here is my last one on a friends Kitfox IV it sits 20" wider 2" higher and 2" more forward than the stock gear that he originally had. Made a whole new plane out of it. 

Edited 9 Jan 2015 by High Country

[akflyer 1427]

I have not measured the new gear I got, but when avid first started making the wide gear it was 14" wider than stock. That was soon changed to 10" wider due to unforseen issues with going wider than that. Just a little food for thought.

What have you done to prove out your "bush" gear? Any off airport pics? Any tests at gross to beat them up n make sure it's not going to tweak the fuse?

I only ask this because I don't want to see a member here get into a bind like the other makers of "bush" gear that was sold untested and pretty obviously not engineered other that using the "that looks about right" engineering method. By changing one angle just a tad you can double or triple the forces on the longereons.

One last thought.... for "bush" work, you want to be able to keep the tail up out of the rocks and sand etc. By moving the axle forwards you are putting more weight on the tailwheel. This turns the tailwheel into a boat anchor on sand and gravel strips.....

I don't want to slow ya down or to burst your bubble, I just want to make you aware of the pit falls of selling "bush gear" that have never seen the bush

[FoxDB 17]

I know I have posted this before but, the Kitfox and Avid fuselage attach points are not angled properly for a cabane type gear. This causes torsional forces to the longerons. I know this by experience.

[akflyer 1427]

I think the cabane gear will work ok on these, but it can't be a straight pull from side to side, the center of the vee has to be dropped down like the Cubs. I had an engineer run the numbers and the straight pull everyone has used so far puts way too much stress on the longereons. I increased the travel on mine as a quick stop gap measure but will soon be fabricating a new vee to change the pull so it will spread the load to both sides, as well as put an additional tube across the top to help keep it from pulling the longereons in.

I think that by using the bungee on it, the travel part is now taken out of the equation and it won't be going metal to metal and bending things like the original springs did. 1.8 inches of travel is just not enough when your heavy and on a rough surface.

[FoxDB 17]

Akflyer, 

I was evidently not clear enough in my post. The angle of the cabane was not what the problem was for me. Problem was the gear leg compression not inline with the longeron but pushing under it caused torsion to the longeron. The cabane does not help the issue either as the legs are in tension and are contributing to the torsion issue in most designs. However I actually provided an independent cabane attach point to allow an inline pull on the longeron.

Hope this helps the explanation, I can take some photos and attach if it would help. I think the best would be the horizontal tube you mentioned to keep the gear attach points from coming together. The angle of the cabane has more to do with the loading on the bungies and the stroke needed during gear deflection. A lower strut attach point with require more stroke for a given tire movement but will require less load.

Dave

[akflyer 1427]

Any pics you can provide would be appreciated! The power of the forum is to help learn from others mistakes and knowledge. I know I won't live long enough to make all the mistakes myself

[FoxDB 17]

Attached are photos of the damage plus the repair to minimize the twisting.

[C5Engineer 1170]

Here is a thread that I started quite some time ago on this very topic.

 

http://www.avidfoxflyers.com/index.php?/topic/2093-lets-talk-gear-geometry/?hl=%2Bbush+%2Bgear

[TJay 1041]

well its been done, I bought a set of high wings bush gear. hope I like it, It has got to be better than stock kitfox 1 gear.

[EDMO 1078]

You will need to reinforce your longeron section there and the section across the front of the seat, I think. Others can give you more info - I like the steel plates welded in better than the plywood glued in. Larger and thicker longerons would be better too.

EdMO

Edited 10 Jan 2015 by Ed In Missouri

[FoxDB 17]

Joey,

Would really like to see some photos of your TK struts. Did you go with 4" or 6" stroke? Also please consider Leonard's suggestion of a horizontal tube between the forward gear attach points.

Dave

Edited 10 Jan 2015 by FoxDB

[Dusty 126]

I have the highwing bush gear.It works well,seems to have plenty of travel and is well made. Highwing gear uses a spreader bar to share the load ,this is a must have . @Akflyer hit the nail on the head regarding forward placement of the wheels ,further back would be better.A kitfox on smooth tyres can be landed with the wheels locked on grass no problem,but it takes a lot of effort to keep the tail up even at forward cg.

[Av8r3400 1179]

Dusty - I have to tell you, All three of the manufacturers of this style "bush" gear have had failures resulting in substantial fuselage damage.  Lowell at Highwing has told me they stopped making this gear due to this problem.  Now if it is working well for you in the type of flying you do, great.  More power to you.

 

I can say, without exception, that if you land hard or hit something during rollout the spring will bottom out and when it does, something has to give.  That something is usually the longeron truss.

 

Bottom line is if you choose to fly the bush with this gear, be careful.