Hello,

I may seem a bit ignorant to those of you building minimax's, but the one I've got I bought last year, ready built by someone back in 1991. Last week I had a heavy landing in it, and there's some damage to the left gear leg. A modification exists for the later models where the RS200 angle brackets that bolt the axle to the leg were elongated to have 3 bolts each instead of 2 for locating to the gear leg. I've attached a diagram of the modified bracket to explain what I mean.

I'd like to replace the current 2 bolt style brackets with the later 3 bolt type. I realise this means I'll have to make them up myself, so I need to know what is RS200? I can see from the plans that it looks like 3/4" X 3/4" aluminium angle that's 1/8" thick, but can anyone tell me what the spec of the aluminium is? For instance, is it 6082 or similar? I'll need to source some here in England and will need to know what to look for before I can make up the new brackets, so any help you can give me will be gratefully received.

Many thanks,

Sandelving aero are your friends here. Aircraft spruce agents. T6061 alloy, they sell it by the foot. That will increase the mauw to 590 lbs.

According to the materials reference sheet RS200 is 1 x 1 x 1/8  6061T6 aluminum angle.

or you can go to Steel undercarriage... I think Team sells it.....

Puff, I contacted David Cooper about the steel undercarriage, but they don't make one for the narrow fuselage model that mine is. They only make them for the 24" width fuselage and mine's 21" wide, so the undercarriage won't fit. As such I'm going to have to make sure that the wooden one I have is properly repaired.

WJNEW37, Thanks for that. Now I know what to order I'll get some in ASAP.

Tomshep,

I had a look on Sandelvings website and entered the dimensions of what I'm looking for. The total price came out at 26.73 euros for a 2ft length that actually cost 4.14 euros. The rest is shipping cost! Is there anywhere in the UK where I can get this stuff? Surely there must be somewhere where the shipping cost is less than 22 euros?

bob.hood,

A word of caution. You will find "architectural" grade aluminum angle easier to find but it is generally only about half as strong as "structural" grade. Architectural grade has square corners. Structurall grade has  round corners. The 6061T6 alloy is structural grade.

Bill

Also, your cart attachment appears to be quoting 1 day delivery shipping charge. Can you possibly save a few Euros by accepting a slower delivery? Just a thought.

WJNEW37,

I hadn't noticed about the 1 day delivery charge. I'll go back on there and see if I can get that down to something sensible. Thanks for noticing that.

WJNEW37,

I went back on their site and found that a 2ft long piece of 6061 angle doesn't have a cheaper shipping option than the one shown in my earlier post. However, if I buy 2 x 1ft pieces then the shipping cost drops to 8.09 euros. There is a snag though. They won't be shipping 1ft lengths till Nov 15th, and then the slow post displays a transit time of 1-2 weeks. So I might not get the metal till the beginning of December!

As an alternative I'm going to see if 6082 will suffice. This is if anything slightly stronger than 6061 and seems to be much more readily available in the UK.

I'll keep you all updated as to what happens.

Hello again,

Now to continue the saga of the 'max. I managed to source some 6082 T6 alloy bar in the UK, and I made up a new pair of brake torque arms from it. I've also made up new longer axle brackets. I went for mild steel for the axle brackets, because although it's a bit heavier, it was cheap and quickly available. I fitted it all together yesterday, and I'll post up some pics of the axle brackets, and the torque arms fitted to the undercart legs. You'll see that I set up the torque arms to be horizontal rather than vertical because I had a bad landing last year and bent one of the torque arms back a bit, and I didn't want to do that again.

Looking at the pics I've just posted up, it occurs to me that I could have shortened the axle brackets a bit in order to save a couple of ounces. However, balancing that is the fact that by making the brackets that bit bigger, the footprint of each is spread over a larger area, and is therefore less likely to cause the kind of compression I found when I took the old ones off. Here's a pic of the state of the undercarriage legs after I'd taken off the old brackets, and you can clearly see how much they'd indented the wood.

The plans call for 6061 t6 aluminum for all parts, aluminum channel in the dimensions called for in plans can only be found in 6063 t52, Technically this means when you do snap rolls in your airplane you will have structural failure at five gee versus six. working with 6063 t52 feels just as strong as t6 so I'm not worried.

Quoted from bob.hood

Hello again,

Now to continue the saga of the 'max. I managed to source some 6082 T6 alloy bar in the UK, and I made up a new pair of brake torque arms from it. I've also made up new longer axle brackets. I went for mild steel for the axle brackets, because although it's a bit heavier, it was cheap and quickly available. I fitted it all together yesterday, and I'll post up some pics of the axle brackets, and the torque arms fitted to the undercart legs. You'll see that I set up the torque arms to be horizontal rather than vertical because I had a bad landing last year and bent one of the torque arms back a bit, and I didn't want to do that again.

Does this mean that the axle can also be mild steel ?

KK

KK,

The axle brackets are normally made of aluminium, so using mild steel for them just added extra strength as well as weight. However, using mild steel for the axle would likely reduce strength in comparison with the 4130 original, so I wouldn't recommend it.

gyrojeffro,

In the UK 6061 T6 is almost impossible to get hold of, but 6082 T6 is readily available. When I looked up the differences on a comparison site I found that 6082 is slightly stronger than 6061, so in the UK I believe 6082 has been used for replacing 6061 whenever new parts have had to be fabricated.

Hello again all,

To continue the brakes saga. Here are a couple of pics of the completed brake attachments on the 'max. Notice the metal brake 'noodles' that turn the cables through 110 degrees. They've got some surface rust on them now from being left in the hangar for the winter, but as they're so cheap and easy to get hold of I might replace them with new ones.

Bob, That's a nice clean looking installation.

Thanks Dick.

I was worried that putting it back together again with the downward facing vertical brake torque arms would only tempt fate into breaking the other one next time. So I decided to redesign the brake fitment to get the fixed end of the band out of the way of the ground. The brake 'noodles' are from a bicycle shop and cost around £2 - £3 a pair. They are nylon lined, and allow me to shorten the brake cables a bit. I've now also fitted one on the throttle cable of one of my other planes in order to allow me to keep the cable from having to loop nearly a foot above the carb. It's much neater.