Hangar 9 33% Pawnee under carraige springs

[chishp]

Guys

I have had one spring go soft on me reducing its length by some 20mm compared to the other. "Question" Is this common? would also like to increase the strength of the standard spring a little ( current ones are 2.11kg/mm ) is there anything out there? Other wise I am going to have to manufacture some in New Zealand. Looking to what ever experience and advise that's out there.
Thanks in advance
Regards
Paul C

[gunny11]

Try www.mcmastercarr.com they have a huge assortment with specs.

[lenb]

We had some manufactured in the US for the pawnee fleet, Taylor Collins spearheaded the effort and I distributed them to the masses. Unfortunately the stock has depleted and its not worth producing them for only a few planes out there that need springs. One option is back load the cylinder with a spacer. Of course this will reduce the shock absorption travel but at least the stiffness will be better

[JimD]

We did this with one of our Porters and it worked very well. Made the plug out of a piece of wood dowel. Seem to remember it being somewhere between 1/4" and 3/8".

[Stew2]

When I had my Pawnee, I initially tried to increase the stiffness with a 1/2" spacer under a stock spring. Worked for 2 flights... After that I did replace the springs with stock springs available through McMaster Carr. Don't know if McMaster Carr delivers to New Zealand though.. But all hope is not lost. Deep in the bowls of the Pawnee thread on RCGroups there is the McMaster Carr part number for those springs. You can at least get the stiffness constant for those springs from that part number and see if you can find a similar spring that you are able to source closer to home. I apologize for not having the time to go dig out that part number from the RCGroups thread, but at least a path exists. Good luck! Hope it shows up quickly and somewhat painlessly.

[kjkavaney]

If anyone finds the McMaster Carr number, please post it here. I have been searching rcgroups but so far no luck finding the number Stew mentions above...
TIA

[JimD]

Here you go:

https://www.mcmaster.com/#9657k95/=1d66wdn

[kjkavaney]

Thanks Jim....I already placed an order earlier today for McMaster Carr so I just added these numbers...
Thank you so much...these will be used on the Czmelak I am mostly done with...I am a bit of a dunce compared to you and Len and Pete on building abilities.....
kevin

[Mosquito]

We can find you a dunce cap Kevin(?) I'll even bring it to Horizon.

[chishp]

Guys,

Many thanks for all the help and advise, I have obtained commercial supplied slightly stiffer replacements sourced here in NZ, the USA supplier was unable to export? I have also carried out the MOD of previous back blogs and fitted the 1/4" bolt replacements to the spring hangers. Trust this will now cure the issue
regards
Paul Chisholm

[stevekremer]

I ordered the Springs that Dr Dolly suggested. I got them in, but they are quite a bit longer. Is this what you used Jim? The chrome is original new, Black is the new one.

[stevekremer]

Also, Does anyone know what these are called?

[lenb]

yes,
Unobtainiaum

[lenb]

OK ok,,

Its a clevis end

[gradiz17]

I have ordered the springs from McMasters that Jim recommended. Pardon my ignorance but can they be changed from the bottom? The top end is VERY securely installed with Loctite etc.

[MarnochS]

Unfortunately, the top of the shock assy is where the spring is changed from. Two bolts secure the cap in place.
the bottom piece comes off too and the piston is removed from the top .....and then the spring.