Ch 9 Main Gear/Landing Brake

This ‘fix’ is in the CP’s somewhere. To put flox in the gap between the metal gear and the fiberglass mounts. When Terry Schubert visited my build he pointed out that I hadn’t done it so its been on my todo list for a while.

Just a lot of flox and a clean up later. There are still a few gaps that I will address next time the fuselage is inverted. Otherwise this little thing is done. Given I’ll be operating way over plans weights, reinforcing this area makes a lot of sense.

Pre treatment

Lots of flox

After cure

After cutting out leg bow material for fitting the brakes and axles, it was time to at last bolt them on!

The 2024 T3 match drilled backing plates needed to be alodined which is straight forward although you have to be very careful as the chemicals are nasty. After the acid clean up its about 90 seconds in the yellow bath. Easy.

I assembled the axles with old bolts, washers and nuts. There is still the wheel pant bracket before I know the exact bolt length needed. The 5″ wheels are the same as I have on my flying plane JZE and these Condor’s have served me well so I’ve gone for the same tire again.

It is great to see the fuselage on three wheels. The front area is still supported as I have more work to do on the nose lift and the full strength is not there until the nose is glassed on the outside.

Left brake

Right brake

Gear on

Time to do the second leg which meant rolling the fuselage to the opposite side.

This allowed me to clean up the inside of the right leg as shown in pic1. The left leg didn’t need so much cut out for the brake caliper as the two axles are in a slightly different position relative to the center of the leg. After setting it all up there was about .3″ difference which I had to fix to make things straight. The legs didn’t care.

Pic 2 shows the cleaned up cutout and pic 3 shows a fitting check of the brake caliper and axle. There need to be clearance between the brake and the leg of at least a 1/16′ or .10″ depending on which part of the plans you read.

Brake cutout left

Brake cutout right

Checking fit for brakes

With the fuselage rolled over to one side the gear legs ends can be tidied up. The lower one just needed the inside area graduated from the BID wedge back to the leg itself. It was quite a mess but worked out nicely with the dremel and sandpaper.

The right leg is now in the air and once up a ladder the task was to make a leading edge cutout so the brake caliper can fit. I made a template, marked it out and spent quite a while with the router and being pretty careful making the curves as you see in pic 2

This took most of the day and operating a high powered tool up the ladder with breathing mask, full face shield and ear muffs is a time to take it slowly. I finished off with permagrit files and 80 grit sandpaper.

I curved all the edges a little too after clearance was established.

Inside leg cleaned up

Caliper fitting

Edges rounded

This was over a few days. The next part was to add a piece of 2024-T3 as a backing plate for the axle bolts. I finally sourced the metal and cut a 3″ square piece for each leg.

I added a two ply BID layup to the leg and placed the cut metal square on it and then clamped the whole thing until cured as in pic 2. You can see it all assembled in pic 1

After cure I reassembled the drilling jig from previous log entries and match drilled the four holes for each leg. You can see the results in pic 3.

The lines drawn were just a way of getting a center line for trimming the metal plate.

Plate in place

Backing plate added

Match drilling

Time to drill 4 holes a side for the axles.

Easy to get the holes in the right place as the axles are still loosly bonded in position on the legs. I did want to make the holes parallel and at right angles to the leg as there is a bit of play in the axle holes. It took a bit of thinking.

The wooden jig piece at the end of the axle is the exact size of axle base. The metal rods extended into the base and then I tightened the nuts to help keep it rigid. This means if you line up the sides your drill bit will be straight. It worked and you get three pics. Hahaha

Drilling straight holes is always a challenge so I’m happy its all good this time.

Axle jig in action

Axle jig

Another axle jig shot…

Next how do I get a parallel surface on the inboard side after making a nice thick pad. Easy. Use the jig still bonded to the other side. Add some spacers as in the first pic. Make them high enough to clear the pad.

Then mount another piece of plywood. Route through that and use the edges as my level to route a flat pad parallel to the opposite side. Works a treat and of course I had to do both legs.

Pad with spacers

Route through the form

Make a parallel surface

Now the axles are in place soon the bolts will go in. There is an issue of ensuring the clamping of the axle is parallel. As you can see in the first pic there is quite a curve on the inboard side of where the bolts and then nuts will go.

I want even clamping pressure so around 80 plies of bid, 40 a side or about .4″ were needed to build that area up ready to be routed parallel so I can achieve even clamping.

Bit of a job and you can see the two sides set up in the next two pics. I again used the teta (high TG) resin as a guard against hi temp braking situations in that area.

Required wedge angle

Right inboard wedge

Left inboard wedge

Once the axle templates were positioned correctly I set them with a few screws. Next the gear legs were removed and I remounted the lasers and re calibrated them with a ruler and straight edge using shims. I mounted the laser boards flush on the axle ends with a bolt and they were solid.

Then it was setting it all up again working out new distances from the centre at the window allowing for the length of the axles from the pads. Then I allowed for toe in and set up the two targets. Then a dry test that I was within range.

It all looked good so I got the axles off and prepped the pads and then made up two 3 ply pads of BID, one for each side on foil. I positioned these, remounted the lasers and then used clamps to get just a little more aiming from the wet BID. It worked a treat and I was right on the cross hairs.

Lots of setting up

Mounted lasers

Position check

This was a few days again lining things up. I repositioned the fuselage exactly on the center line of the bench and parallel to the end and all square.

Next was to get a straight edge hard up against the longerons and measure straight up. 2.5″ less than plans and of course both sides need to be the same. I taped two rulers together and then taped a backing square of aluminium to keep it from bending. Checking was easy once I was set up.

Finally distance forward and aft needed to be the same both sides. In other words the axles the same distance from the rear or front so the aircraft can taxi straight once th nose wheel is correct. I was .26″ out so had to move the axle forward one side and back the other. So they are not 100% center of the gear leg but there is plenty of side meat and parallel wheels are important.

You can see plumb bobs located on the axles down to the big straight edge. A great way to get real positions.

This all took a lot of thought. You can see view holes in the jigs to help get lines visible on the gear pad template.

Checking the center line

Setting the axle height

Checking axle forward location