I am not an A&P! Do not take this page as gospel. The maintenance manual is very sketchy for our birds, so I am merely trying to add some detail to the instructions therein. If what I say here seems to disagree with the manual, the manual is correct and that is the way we did it.

This covers only the main gear donuts. I didn't change the nose gear donuts as they were apparently done at the time the nose was rebuilt some 2000 hrs ago. The nose still sits at nearly the specified height and can be bounced, so I saw no need to replace them.

The washers were neither large enough to cover the donut surface nor strong enough for the load, so another piece was needed to go against the rubber. From the sign shop on field, I obtained 4 3.75 squares of 1/4 steel plate. After drilling holes, I stacked it up as shown in this picture:

• Nut
• Washer
• Plate
• 8 Donuts
• Plate
• Washer
• Nut

Run the nuts in until it is finger tight. I mean really finger tight! Align all the donuts carefully and arrange the plates so that there is as little donut sticking past them as possible. Tighten slightly with a wrench and recheck the alignment. Now check and record the dimension from the outside of the plate to the outside of the plate (mine measured 8 1/2 inches)

Unless your house is a meat locker, room temperature is warm enough. Begin tightening the nuts slowly, no more than a 1/4 turn at a time. As the stack compresses, let it sit longer between tightenings.

If you have a smaller diameter rod, the donuts may slip out of alignment. If this happens, loosen the nuts and re-align, rotating the donuts that slipped a half turn before re-tightening. Re tighten, but not to the point where they were when they slipped. Let them sit longer between tightenings to minimize a reoccurrence. We were worried initially about a portion of the donuts sticking past the edges of the plates. When we loosened the stack to re-align it, we found no scoring on the donuts and they came back to "flat" before we were ready to re-tighten the stack.

You will need to compress the stack at least 1", more is better.

The day before you need them, put them in a normal refrigerator. They will need to cool at least 24 hours.

This is essentially a one man job. There is a lot of "third hand" assistance needed, for advice, steadying something or simply supervision and criticism. But your A&P can do it himself with you supplying the third hand or supervising you.

With this in mind, unless the shop is awash in manpower, do it one leg at a time. This means jacking only one wing at a time which is much safer.

I would recommend that you pre-order the two pairs of pins for the pivot pins. Unless you are very lucky, you are going to bend the ones on the donut pivot (Which MUST be removed) and there is no easy way to get the pin out of the main pivot. [part numbers: main pivot retainer pin, MS20392-1C61. donut pivot retainer pin MS20392-1-41]

I would also recommend that unless you know they have been replaced since your bird was new, that you replace the abrasion washers. [Part number: Abrasion washer 169-810000-119. Tulsair has them.]

The picture shows the swing arm as it looked before we started. Note that the donut pivot is completely inside the casting. This is why they need changing.

Pull your Mouse's pants leg down, Clean out any debris on top of the casting (I found an old dirt dauber nest on one side of mine. Disconnect the brake line where it comes out of the wing and cap the stub. Cap the line from there to the brakes if you can, but don't worry about it as you will have to flush that before bleeding it anyway.

Remove the wheel cover and axle cotter pin and loosen the axle nut. Remove the inside brake pad. Now jack the wing up enough to remove the wheel. Lay the wheel under the swing arm for safety and cover the hub to keep dirt out of the bearings.

I saw several methods for removing the Jo-Bolts discussed, but as the shop manual says in at least 2 places to grind the heads off, that is what the A&P decided to do. We taped around the bolt head to protect the flange as much as possible and went to work. We had an air grinder with a 3" cutoff wheel and an electric grinder with a 5" cutoff wheel and used both of them. Do not attempt to "cut" the head off, there is too much risk of damaging the leg if you get too close. Hold the cutoff wheel perpendicular to the leg and just eat it away. It only takes about 10 minutes per bolt.

When you think you are close, use a 3/8" punch to tap on the shaft. The remainder of the head will separate before it is all ground off, so take advantage of this and save the possibility of grinding into the leg itself. If it doesn't separate with a smart tap, grind some more.

Stop working on the first one when the shaft separates from the remainder of the head. Do the other one then drive both shafts into the leg. I would venture the odds of the leg falling off as soon as the bolts are gone as astronomical, but that is why the tire is sitting under it as shown in this picture. It cannot come all the way off until you move the tire.

Push the pants leg back up a little so you can grasp the leg firmly. Push the tire out of the way and wiggle the leg off. The entire assembly even with the brake assembly weighs less than 10 lbs., so removal is easy. If available, blow out the entire area under the casting with an air hose and take it to the bench for disassembly.

Remove the pants leg and set it aside. If you had to loosen the fitting where the hydraulic line goes down the leg to get access to the Jo-Bolt, remove it and set it aside. Remove the nut on top of the stack. It is 1 7/16" self locking, so someone must hold the leg down while you take it off. Inside should be at least one steel washer and a rubber washer (referred to as the abrasion washer in my service manual). Throw the 2 Jo-Bolt ends away (unless you just have to keep things like that as souvenirs) and set the washers and nut aside.

This picture shows the pivot pins and the retainer pins as red "T"s. The Ts show the location of the heads of the pins as found on my gear. Now, it is take stock and make decision time. The main pivot pin must be removed to get the donut pivot retainer pin out. But, the main pivot retainer pin is installed from the front with the cotter pin inside the housing. The least bit of corrosion or simply slight turning of the pivots will bind the retainer pin to the point that it must be driven out. If it is not free, you must remove the donut pivot pin so the swing arm will go forward enough to get to the back of the main pivot pin. Removal of the donut pivot pin without first removing the main pivot pin can only be accomplished by bending it along the bottom of the donut holding plate. That's why you needed to have new pins available before you started besides the fact that these $3.00 pins should not be re-used.

Once the pin is removed, remove the pivot pin. A deep well socket works well here to protect the zerk fittings. The swing arm can now be moved far enough to remove the donut stack. There is a plate on the bottom of the stack which must be separated from the bottom donut.

Since you must install and load the donuts quickly once they are removed from the refrigerator, have everything ready to go first. Clean all the parts as desired. Clean the pivot pin holes and pivot pins completely. A little Scotch-Brite works well. Test fit the pivot pins to insure that they will go back in easily. Work with them until they do. The donuts will not slide easily onto the shaft. We found that a can of white grease and a brush helped. Have the 1 7/16 socket, extension bar and breaker bar or long handled ratchet close by. You will also need the third hand, so have him/her close. Put the spacer back on the shaft. Remember, once you remove the donuts from the refrigerator, you need to get them on without stopping.

Remove the donut stack from cold storage and release whatever is holding them compressed. "Screw" each donut past the threads on the shaft and slap some grease on the shaft. Push the donut all the way to the bottom. After all 8 donuts are on and as far down as you can get them, insert the shaft into the casting. The hole in the casting is only a little bigger than the shaft and the donut flanges are almost as big as the inside of the casting, so lining up the hole and shaft may take some doing.

Place the rubber abrasion washer on the shaft. If you are using a new one, a little grease on it will help. Once it is completely on the shaft, put the steel washer(s) on and use the socket and extension to force them to the bottom (the third hand will be holding the assembly down for you). I have small hands and could start the rubber washer and hang the steel washers, but I could not start the nut. Put the nut in the socket. You may have to pad it up with some paper towel to keep it from going to the bottom of the socket. Get it started, but make sure it is not cross threaded.

You will need to place the swing arm back into the donut pivot to hold the stack while you tighten it up. Then tighten the nut to the required dimension. The position shown in the picture above is nearly correct, so get close to that before you even start to check with the ruler. Now, you can relax a minute.

Reassemble the pivots. Note the location of the retainer pin hole before pushing it in and try to align it as closely as possible. If the alignment is close, an ice pick will finish it up. Otherwise, back it out a little and gently turn it as needed then push it back in. Repeat as necessary until it is lined up. Insert the retainer pin also being aware of the alignment of the cotter pin hole. You want this hole in a direction that will allow easy installation of the cotter pin. Install the washers and cotter pins.

You are now ready to re-build your Mouse. Do a little preventive maintenance here before you start. Re-pack the wheel bearings if it has been a while. Check the air in the tire. Re-grease the pivot pins, remember they have been subjected to cleaning while they were out and the inside of the bushings have been cleaned.

Replace the Hydraulic line if it was removed. It is easier to start the fitting with the pants leg off. Do not tighten it up. Re-install the pants leg and push it all the way down. Test fit the Jo-Bolts. You may have left some deformation of the hole edges when you drove the old ones out. The compression part should slip in easily but the barrel part will be a force fit.

Insert the leg into the wing bracket and push it up into position. Visually check that you can align the holes and slide the tire under the leg. Insert both Jo-Bolts and tap them all the way in. Now, install the Jo-Bolts using whatever tool you have available. The hard part is done.

Re-connect the hydraulic lines and tighten them up. Re-install the wheel, axle nut and cotter pin. Get the plane off the jacks. Bleed the brakes and re install the pants leg and wheel cover.

This picture shows the after installation. The donut pivot pin and part of the donut support are visible below the casting. This is how it should look.

Clean up the tools and work area, pull the bird out into the sunshine and give it a bath. And then a test flight.

Now you are done