Rubber Discs for Shock Strut

Homebuilt Aircraft & Kit Plane Forum

Help Support Homebuilt Aircraft & Kit Plane Forum:

karmarepair

Well-Known Member
HBA Supporter
Joined
Jan 13, 2011
Messages
575
Location
United States
this should cut round rubber washers cleanly....

A mat board circle cutter might be worth a try, a LOT cheaper than the tools sold by McMaster Carr.
 

challenger_II

Well-Known Member
Joined
Jul 15, 2009
Messages
451
Location
Fisher County, Tx. USA
My bet would be that die cutting would work better than fly cutting: well-lubed, the die would make a cleaner cut, with fewer imperfections that would need to be addressed.

It still appears that casting the doughnuts is the simplest, least expensive option.
 

Mad MAC

Well-Known Member
Joined
Dec 9, 2004
Messages
780
Location
Hamilton New Zealand
Update: Found a source of 2 1/2" x 7/8" bore x 1/2" 60 duro rubber doughnuts. Research has determined that the Mooney M20 pucks are 65 duro. I ordered a batch, so we shall see how this goes.
You couldn't give the source for those rubber doughnuts, just for everyone's future reference.
 
Last edited:

challenger_II

Well-Known Member
Joined
Jul 15, 2009
Messages
451
Location
Fisher County, Tx. USA
Show and Tell time:

I really should have done this, early on. It would have simplified the discussion.

This is my gear arrangement, as built. I want to replace the coil spring with rubber discs, as the original plans show.
Looking closely, you will see that the spring is mostly compressed, and the aircraft is at rest, and empty. Add my 230#, and the springs are close to bottomed-out. Ergo, not much spring left, when landing.
 

Attachments

Vigilant1

Well-Known Member
Lifetime Supporter
Joined
Jan 24, 2011
Messages
6,760
Location
US
Show and Tell time:

I really should have done this, early on. It would have simplified the discussion.

This is my gear arrangement, as built. I want to replace the coil spring with rubber discs, as the original plans show.
Looking closely, you will see that the spring is mostly compressed, and the aircraft is at rest, and empty. Add my 230#, and the springs are close to bottomed-out. Ergo, not much spring left, when landing.
With the arrangement you have, is there sufficient >damping< (absorption of energy so there's little/no rebound)? It looks like the only damping you get now is from the scrub of the main wheels against the pavement/ground as the gear splays out on touchdown, and it's entirely possible that this is sufficient (or would be sufficient if you had more gear travel).
 

Tuneturkey

Well-Known Member
HBA Supporter
Joined
Dec 29, 2018
Messages
84
Location
10113, Hyde Park Ct., Baton Rouge, LA 70816
Your solution with the rubber spacer is a great fix for me. My nose wheel has a space of 4" for insertion of a spring or the rubber grommets. the nose wheel strut is 3/4" OD is perfect. Question though: How viscous is the 60 duro rubber. Max weight on the nose wheel is close to 100# TOW. Will the rubber compress with three of these in line on the strut? What is the deflectiion/lb of load for 60 duro?
 

challenger_II

Well-Known Member
Joined
Jul 15, 2009
Messages
451
Location
Fisher County, Tx. USA
That is the $64,000 question. It is why I am looking for 30, 40, and 50 duro discs so as to make a comparison, and get the right "ride".
The original plans, which date to 1932, called for "20-38" rubber. I have found no correlation of that spec to modern rubber specs.
 
Top