Landing Gear

Brakes and BRS Bridles

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Awhile back I ordered some black plastic clips from AliExpress.com to hold the bridles for the parachute in place. This weekend I decided to put them to use. When I got started I also decided to tackle the brake cables since it looked like I could route those with the bridle clips too.

FC-30 3M Selfadhesive Nylon mounting flat pole wire cable clamp
FC-30 3M Selfadhesive Nylon mounting flat pole wire cable clamp

The brake cables exit the fuselage near the front of the landing gear on each side, I added a small grommet to this hole to reduce chafing.
Grommet for brake cable
Grommet for brake cable

To keep the cables from flapping in the breeze I added a couple of rubber lined cable clamps to the landing gear bolts. The cable routed through the clamps then down the landing gear leg along the bridle that is secured with the plastic clips.

Bridle and brake cables secured with clips
Bridle and brake cables secured with clips

The grade cable the runs around the from of the gear into the caliper.

Break cable into caliper
Break cable into caliper

I also used the bridles clips inside the fusealge so they don’t get tangled up with other things. These clips are a little too tall so they don’t clamp the bridle. I put a small piece of foam on the top on in the picture below. Next time I’m at the hardware store I plan to get some self adhesive black foam weather striping to use in the few places where this matters.

BRS bridle secured with clips in cockpit
BRS bridle secured with clips in cockpit

I plan to add maybe one or two more clips inside the fusealge but I need to climb in and make sure I don’t place them in a position that my elbow might hit. Right now the seat is covered with parts for electrical wiring so I’ll do that some other time. If the 3M sticky tape does not hold up I plan to secure the clips using a couple of tiny wood screws but so far the 3M tape seems adequate.

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Disc Brakes

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I have thought about adding inexpensive and lightweight bicycle disc brakes to my Minimax for a long time. The main stumbling block is fitting the rotor to the AZUSA Tri-star 6″ wheels. On http://www.lonesomebuzzards.com Walkabout posted a brilliant, cheap way to mount the rotor. More about that later. With the most difficult part resolved it was time to get started.

Finding inexpensive rotors that did not look like something out of the movie Saw was a little difficult but since there is a nearly infinite selection I did finally find a set I liked. I settled on the Gymforward YD-ZXC-SCP001 160mm rotors.

I could have bought two of nearly any bicycle caliper but I wanted something a little unique. If I used the same caliper on the right and left one side would require a longer cable, look odd and possibly cause uneven braking. Finding a set of right/left calipers was difficult until I searched for scooter calipers. Ordered these calipers for $20 from a Chinese seller and it only took about a week for them to arrive. I’ve seen these sold on other sites but this model is the only right/left set of calipers I’ve found.

The mounting bolts on bicycle calipers are spaced 51mm apart. These scooter calipers use a 50.5mm spacing. To figure out all the measurements I used a free on-line CAD application OnShape. After finding a drawing for bicycle caliper mounting bolt measurements I designed the caliper mount in OnShape altering the measurements just enough to account for the 0.5mm difference. The mount is fabricated from 2″ x 2″ x 0.125″ aluminum angle.
Also used OnShape to design the rotor adapters. I knew with the proper bolt spacing the rotor would be perfectly centered. Using OnShape assembly I was able to verify the design before drilling a single hole. 

I used 1.25″ x 1.25″ x 0.125″ aluminum square tubing. Each wheel needs three adapters and each adapter requires two cuts and three holes. Very simple to make.

One of the main reasons I am doing this is to have a parking brake. With that in mind I started looking for a brake lever that has a locking mechanism. Found the perfect lever that allows me to set the lock with my pinky finger. Simple, elegant solution.

Brake lever
Brake lever latched

The final result looks great, I hope they perform just as good!

Caliper mount
Caliper mount

If you want to build these parts yourself you can download the plans: Caliper-mount-drawing.pdf

Covering Gear Legs

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Asked David at TEAM if the landing gear legs need covered and he replied that it was optional. I decided to cover them, used one piece of cloth just like the rudder or fin.

I made sure the seam was on the bottom to help hide it.

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Landing gear leg

The outside looks great with no seams.

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Landing gear leg

I just need to do a little ironing and they will be ready for sealing.

BRS Bridle Routing

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Time to route the BRS bridles from the axle to the parachute. I first attached the bridle to the axle.

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Bridle lopped around axle

The most logical place to enter the fuselage is straight up and there already happens to be a plywood block there so I cut a short in it.

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Slot for BRS bridle
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Slot for BRS bridle

Next a slot in the seat is needed.

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Slot in seat for bridle

From there it’s routed through the fuselage top just in front of the rear spar carry through. Be sure that the bridle is on top of the seat belt, not under it!

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Bridle slot under turtle deck

At this point the right and left routing differ. The left bridle needs to go over the shoulder harness over to the right side. Starting with the third stringer on the left, ending with the third stringer on the right a notch is cut into the top of the stringer to make room for the bridle.

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Shots cut in center four stringers for bridle
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Bridle slots in stringer

For aesthetics each slot is covered with a piece of 1/16″ plywood. This piece must easily break away so I only glued one side, the fabric will hold it in place.

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1/16" plywood cover bridle slot

The next hassle of the BRS is the egress port. Two stringers must be modified so they can break away.

Landing Gear Struts

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The landing gear struts are pretty easy to make once you have a good method. My first one ended up with one hole drilled off-center. These are made from the RS-402 that is also used on the fin. Aluminum fin strut brackets to the rescue!

To get the hole drilled on center put one of the fin strut brackets between the axle and the strut, be sure to align the hole in bracket with hole in axle. The fin strut bracket is on drawing 10 bottom right.

Align the drill bit through the axle and bracket hole, then drill through the strut. Be sure to keep the bracket flat against the axle.

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This is what the brackets look like.

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Angled Axle Hole

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Each landing gear leg has a 1 1/8″ hole for the axle to pass through. Drilling this hole is a little complicated since it must be drilled at 37°.

First I layed out the holes for the axle brackets.

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Then I made the guide block as explained in the manual. I also drilled a hole in the side of the guide block that lines up with the axle bracket.

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Using a 1/4″ bolt I aligned the guide block and drilled the hole through the landing gear leg.

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Removed the brackets and drilled the 1 1/8″ hole from both sides.

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I thought the plug looked kinda neat.

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After a little sanding it looks great.

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Making good progress, next I will assemble the gear and make the aluminum struts.

Main Gear Axle

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The four holes in the main gear axle must be parallel to one another and drilled perfectly through the center of  the round pipe. With a little planning this was easier than I anticipated.

To ensure the holes are centered on the axle I clamped two aluminum angles to my drill pres to hold the axle centered on the drill bit.

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Using a small rod in the chuck I measured between the angle and the rod. When the measurement was the same on both sides I tightened the clamps.

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Drilled one of the outer holes first. Moved the axle to the next hole. In the first hole I placed a drill bit into it. Now I can rotate the axle until the bit in the first hole lines up with the bit in the drill press.

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When drilling the holes I first drilled a small hole then drilled out to the property size. Both times I verified that the rotation was correct.

One of the center holes is off about 0.010″ close enough for this bird.

Gear Hinge on a Diet

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My friend Fred helped me cut the hinges down to size. He used a cutter on the mill since neither of us had a better way to cut it.

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Cutting off the excess saved 6oz per hinge for a total of 3/4lb saved. That might not seem like much until you consider the whole airplane must be under 278lbs.

To better understand why saving 12oz is important, my altimeter alone weighs 10oz. Every ounce saved is an ounce I can use for improvements.

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Gear Hinges

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Back from vacation, time to make more progress on the Mini-Max. Need to get the fuselage on its own wheels so I can move it around easier.

A couple of piano hinges are used to attach the main gear legs to the fuselage. The plans show the RS-805 hinge being 1.5″ wide, included in my kit are 3″ wide hinge. Contacted David at TEAM and he said the 1.5″ is no longer available and to get the correct pin size they had to use the larger hinge. He also said it is OK to cut 3/4″ off each side to make it 1.5″ wide. Marked and center punched all the holes.

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The hinge pin is 1/2″ longer and needs bent, after drilling and bending the hinge pin they look like this.

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If you look closely you can see I have also marked a straight line on each side. This is the 3/4″ that can be removed from each side. Cutting that of should save 8-12oz. I don’t have anything that can cut it without wasting hours of my time so I will deal with that some other day.

Main Gear Progress

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Glued the RS-540 sheeting to the other side of both main gear legs. Once dry I decided to first cut the 37° angle at the top of each leg. Very important to remember that there is a left and right leg and you need one of each not two of one side 😉

I cut a thin piece of wood from a 2×4 to extend the fence on my table saw. Set the blade to 37°

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With some trial and error using some scrap I adjusted the fence. It ended up looking like this.

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After testing this setup on three pieces of scrap I ran the landing gear legs through. One forward and one backwards so I ended up with a left and right leg.

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The end result looks pretty good.

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This ended up being a little easier than I anticipated. With a little planning and patients I can sometimes do good work.