Starting Extended Gear Mod on M-5

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JTCaturia
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Starting Extended Gear Mod on M-5

Post by JTCaturia »

Hello All,

I am about to replace my stock landing gear, and replace with HD ext landing gear, oleos, and new 6" wheels with double puck brakes, matched up with 31" bush wheels. All Airframe Alaska parts. Also new Oleo springs from Maule. I do have lift rings already installed.

I spoke to Maule this summer and it sounded like they retested the "drop test" and the hydraulic oil originally used may have change in viscosity since the 1970's. Wondering what is the best choice for hydraulic fluid to fill the oleos?

Would love any wisdom on precautions, gotchas, techniques that can be passed along before we dive into the project.

Cheers,
Jeff
1976 M-5-210C

maulem5210c
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Post by maulem5210c »

If you purchased the new style springs part number 4161B then yes you are correct. The oil that maule recommends is API GL-4 or GL-5 85W-140 gear oil.

Please PM me and I'll email you the letter maule sent with my new springs just a couple of weeks ago. Not only does it talk about the new oil, but also the need to machine the old oleo piston and oleo bearing to the correct dimensions.
1977 M5-210c (upgrading for back country fun)
Building RV-8

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UP-M5
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Post by UP-M5 »

acquire some extra o-rings for the oleos. and plan on spending a bit of time sanding and polishing on the inside bore of the new oleos. as supplied from airframes, they are very sharp and tend to cut the o-rings as you push the cartridges into the oleo.
M5-235

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Andy Young
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Post by Andy Young »

So the tractor hydraulic oil is no longer recommended? 85W-140 is MUCH, MUCH heavier than the hydraulic oil, which is somewhere around 20 weight. The other recommend (optional) fluid for the oleos, per my maintenance manual, is 10W-30 motor oil, so similar weight to the hydraulic oil. Why the change to the drastically heavier oil? Seems odd, since nothing else has changed. Seems like it would raise the damping rate enough to make the gear noticeably stiffer on landing. Is it an attempt to minimize oil migrating past the O-rings?

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crbnunit
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Post by crbnunit »

I installed the extended gear and reused my old springs. Didn't have the time or the equipment available to turn the bushing to fit the new springs. I used the tractor oil and have had zero problems. Why the switch? Yes, plan on an hour +/- polishing and de-burring the inside of the extended olio tubes. Extra o-rings are an excellent idea and they are cheap so several sets won't break the bank. I posted the Aircraft Spruce part numbers somewhere but I can't find them via search. Maule has them as well. I found a press was extremely helpful on reassembly. You have to compress the spring a bit and it would be difficult without an extra set of hands. The press made it easy.
You have to make up your mind about growing up and becoming a pilot. You can't do both!

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crbnunit
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Post by crbnunit »

Found them!

Main gear bolts"
4 NAS6606-D38 bolts
2 NAS6606-D18 bolts
2 NAS6606-21 bolts
6 AN310-6 nuts
2 AN365-624A nuts
32 AN960-616 washers
32 AN960-616L washers
10 MS246655-283 cotterpins

Ski bolts for main gear:
4 AN6-34 bolts Upper gear bolts (don't know NAS number)
4 AN5-11 bolts (I think these are cable attach bolts)

Tail wheel:
2 AN5-15 bolts
1 AN6-22 bolt
Nuts/washers/cotterpins

Brake pads for dbl puck calipers:
Cleveland #066-10600

Olio o-rings:
2 AN6227B-27 or MS28775-222 (this is the bigger one)
2 AN6227B-14 or MS28775-116
These can be found under brake parts at Aircraft Spruce.
You have to make up your mind about growing up and becoming a pilot. You can't do both!

G-MAWL
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Post by G-MAWL »

Fitting the o rings is easy. I used a Flexhone to clean the bores. Took all of 30 seconds.

Lightly oil or spray with silicon the cap and strut around the bolt holes. Fit the cap where the tapped holes aren't seen.
Fill the holes with some epoxy putty (car body filler might work) proud of the holes in the strut. When set put a hose clamp around the top of the strut to hold the epoxy plugs in place. If you've oiled correctly they wont stick !
Pull out the cap and you should be left with a perfect bore and nothing to cut the o rings going in. You might have to clean of some of the epoxy from the bore but the idea is to have a flush smooth surface.
Assemble as normal, take out the epoxy plugs, rotate to line up the holes.

I've seen some where a chamfer has been made in the inside of the holes in an attempt to fit the o rings. Not a good idea as it reduces the area the bolt has to bear on. Elongation of the holes vertically almost guaranteed.

These are not "shocks" as we know in cars. They are not valved and have equal (more or less) dampening in both directions.
In a perfect world there would be a resistance from the oil when the strut extends with no resistance on the way in so it was ready to absorb the shock going out again.
In other words it's ability to be in a position quickly to absorb energy is restricted by the oil. i.e the piston should be sealed in the bore with a one way valve to allow a fast rebound with a metered hole controlling oil flow on the outward stroke.
Also the clearance between the piston and strut cylinder is quite large. The oil you want is the one which suits your gross weight and landing technique ! Derek

JTCaturia
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Post by JTCaturia »

Thanks for the heads up on the gotchas. It seems the O-ring is the tricky part. Crbnunit, thanks for the part numbers, I will order up a few extra. I will be helping my A&P do the work. This is great info to keep us on the right track..
Jeff

1976 M-5-210C

pilot
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Post by pilot »

Four feeler gauges will work on the o-ring install as well.
I can't remember if I fired six shots, or only five.....


M-5 220c, circa 1974
EAA #428061

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Andy Young
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Post by Andy Young »

When I did my latest set, the fit between the head and the cylinder was so tight that I couldn’t get feeler gauges in there.

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Njacko
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Post by Njacko »

Be prepared to file, grind, shim, drill, ream, mill or otherwise beat up the new legs to persuade them fit the fuselage - after a fashion. We used a milling machine, but that was justly criticised as a gun-plumber’s perversion. :) Most self-respecting engineers would hit the legs with a grinding wheel.
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UP-M5
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Post by UP-M5 »

i also had to do a fair amount of grinding to get the legs to fit into the fuselage lugs.
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gbarrier
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Post by gbarrier »

Keep as square as you can if you use a grinding wheel. Install the back first and then twist/persuade the front into place.

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Njacko
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Post by Njacko »

I gather that the extended gear has been “temporarily out of stockâ€￾ at Airframes Alaska for a few months:

https://www.airframesalaska.com/Extende ... -4022x.htm

Does anyone know why, and/or when AA will have them back in stock, or anyone else with a set for sale?
MX-7-180 N280SA

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bobguhr
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Post by bobguhr »

Spoke to Airframes, apparently they are playing catch up across the board due to down time from a facilities relocation.

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