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Webber gear mod -- mod printer friendly version
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dannparks
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Posted Sunday, August 4, 2013 @ 01:28 PM  

In doing initial taxi tests, I really noticed how stiff the Webber gear rubber "springs" (new ones) were even on hard bumps, they didn't really move at all. Also the gear had compressed about an inch (which is OK), but when weight was removed from the gear, it did not expand to fully extend the gear arm mechanism. Unless the gear arm is fully extended, it will not fit properly into the snail.

I decided to look at replacing the rubber with real metal springs and found some springs from Grainger that seem to fit the bill. They are pre-compressed a bit on install, so they will fully extend the arm for retraction. The arm compresses about 1/2" on the ramp at gross and rides well over bumps, but doesn't compress too much over large bumps. And there seems to be enough drag in the system so there is no bouncing oscillation.


Old rubber


New springs


New springs

These are Grainger No. 44U640, 1.25" x 5.5", with a 264 in/lb. spring rate each. Of course I'll have to fly it (very soon) to really test it out, but so far it is a real improvement.

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Dann Parks • RF4D #4051 N2188 • now flying!
Pictures at: https://picasaweb.google.com/111628310900713778468/RF4D_N2188?noredirect=1

jb92563
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Posted Thursday, August 8, 2013 @ 10:05 AM  

Thats a great improvement. I have the same problem with the rubber shocks so I may go your route as well.

Thanks for the details. I'll be waiting on your flight review to see how it works out.

Did you use a bushing/spacer of some sort to keep the spring centered on the rod?

I could make a set on my lathe out of nylon or teflon that I have on hand.

--------------------
Ray
RF4D #4057 N-1771 Rectimo 1400cc
http://picasaweb.google.com/jb92563/FournierRF4D
http://www.touringmotorgliders.org

dannparks
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Posted Thursday, August 8, 2013 @ 11:56 PM  

I had thought about making some kind of spacer or bushing, but the coils of the spring are quite wide and there is only a 5/8" space in the middle. So they fit fine just by themselves over the 1/2" rod. I had also thought about sliding a piece of 1/2" ID x 5/8" OD plastic tubing over the shaft to help center the spring, but still allow the spring to compress all the way. I don't think it will be necessary, though.

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Dann Parks • RF4D #4051 N2188 • now flying!
Pictures at: https://picasaweb.google.com/111628310900713778468/RF4D_N2188?noredirect=1

jb92563
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Posted Thursday, September 19, 2013 @ 09:57 AM  

Hey Dan,

Any update on how the springs are working out for you?

How are they on landings? Do the bounces keep going or do they dampen out pretty quick?

I have a somewhat lumpy dirt runway so those springs could be quite beneficial at smoothing out the landing roll if they are soft enough.

--------------------
Ray
RF4D #4057 N-1771 Rectimo 1400cc
http://picasaweb.google.com/jb92563/FournierRF4D
http://www.touringmotorgliders.org

dannparks
Sergeant Major

Gender: Male
Location: Parkside Airpark, Battle Ground, WA
Registered: Oct 2006
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Posted Sunday, September 22, 2013 @ 01:16 PM  

Well, I only have two landings on the springs at this point, but I think they are doing exactly what they are supposed to do. They absorb bumps well and don't bounce too much. Since your Webber mod might be a bit different dimensions, measure and get a spring length that allows about 1/4" pre-compression when installing. They have lengths every 1/2" so you should be able to find the right size.

Let us know how they work for you if you do it.

--------------------
Dann Parks • RF4D #4051 N2188 • now flying!
Pictures at: https://picasaweb.google.com/111628310900713778468/RF4D_N2188?noredirect=1

dannparks
Sergeant Major

Gender: Male
Location: Parkside Airpark, Battle Ground, WA
Registered: Oct 2006
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Posts: 376

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Posted Monday, May 26, 2014 @ 11:24 AM  

Hey Ray, did you ever try the springs? After a bunch of landings, I think they are working great - the perfect softness to absorb the short drop after a slightly tail-first landing with no bounce, and a smooth ride over taxi bumps. Let us know how they work out.

--------------------
Dann Parks • RF4D #4051 N2188 • now flying!
Pictures at: https://picasaweb.google.com/111628310900713778468/RF4D_N2188?noredirect=1

jb92563
Second Lieutenant

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Posted Thursday, June 26, 2014 @ 07:46 PM  

It will be a little while before I get to work on the springs but I'll be going that route as well so its good to hear that yours are working out well.

--------------------
Ray
RF4D #4057 N-1771 Rectimo 1400cc
http://picasaweb.google.com/jb92563/FournierRF4D
http://www.touringmotorgliders.org

Jorgen
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Posted Sunday, August 17, 2014 @ 04:43 AM  

Hi Guys,
I had an opportunity to look at the Stemme S6 at a local air expo a couple of weeks ago. It's got nothing on Fournier's of course but you have to give Stemme credit for their uncompromising designs were gliding ability is always high on the list. I noticed a feature I was not aware of, the "polymer" suspension, somewhat similar to but supposedly more advanced compared to the rubber cushions used in the Webber gear mod. Not that there's anything wrong with the springs but keeping weight down is also a priority.

Close up of the gear leg that folds backwards and in, note the orange polymer cushions.

Closer look at the suspension.

I don't know where these cushions might be available, maybe Stemme would help. If you have the odd pile of 250 000 EUR lying around you could of course go ahead and buy the Stemme S 6;-)

May the 4s be with you/ Jörgen

P.S. When the local Stemme dealer heard I fly an RF 4 he immediately asked if I was willing to sell it. I said no of course. D.S.

[Edit by Jorgen on Sunday, August 17, 2014 @ 04:46 AM]

jb92563
Second Lieutenant

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Posted Friday, October 10, 2014 @ 04:08 PM  

Quote:
Originally posted by dannparks

Hey Ray, did you ever try the springs? After a bunch of landings, I think they are working great - the perfect softness to absorb the short drop after a slightly tail-first landing with no bounce, and a smooth ride over taxi bumps. Let us know how they work out.

I ordered the springs as well, but the 6" version. Getting it ready for Jerry from Washington, who I think you met recently.

Those rubber shocks do not stand up to the constant load as they seem to be permanently squashed when I lifted the load off the wheels yesterday to take measurements.
The springs should be the perfect solution.

--------------------
Ray
RF4D #4057 N-1771 Rectimo 1400cc
http://picasaweb.google.com/jb92563/FournierRF4D
http://www.touringmotorgliders.org

Roger.Camp
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Posted Monday, October 13, 2014 @ 05:18 AM    YIM

Hi Folks,

The Fibroflex doughnuts can be obtained from the manufacturers Läpple.

http://www.fibro.de/en/standard-parts/product-groups/elastomerfedern0.html

Roger

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It takes 1.460 bolts to build an aircraft and 1 nut to spread it over the landscape

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