[AndrewTO]

Hey all!

AndrewTO here, your friendly, neighborhood machinist man. (yeah, cheesy, I know)

A fellow member recently posted in the Let's Talk About Shocks section with need for a part to keep his ride running and I was reminded of the ever-classic "rear fork" design we all know and love. You know, the one that many have with a broken rear crown?

My proposition is to fabricate some crowns for owners that have a frame they'd like to use again, but can not because of this broken piece. Material would be 6061 T-651 aluminum, machined from billet (I can source it easily and inexpensively). It would NOT be an exact duplicate! I don't want to fabricate something that would just break again. I'm interested in fabricating a piece that is a solution to the problem. While I don't have any fancy force analysis software to use for modelling a piece, I do have experience with this kind of thing and plenty of experience at machining (search my username with a keyword adaptor to see what I did with my ProFlex - I gots skillz!). I'm more than confident I can fabricate a sturdy piece that is still attractive (subjective) and relatively inexpensive. Again, the goal is to produce a solution to the problem.

Speaking of problems ..... BIG one. I don't have this piece in my posession to use as a blueprint. This is where I need help. I'm looking for one owner of this frame that has a crown still intact that would be willing to ship it to me to use as a reference piece. This piece would be measured, then returned. This piece would NOT be damaged in any way - it will only be used for sizing reference, nothing else.

Yes yes, I know, "isn't this spam?". I already P.M.'ed Rumpfy about this and Eric was kind enough to give me a go ahead with this post (THANKS Eric! :thumbsup: ). My intention is more about helping people getting their frames "up and running" again, more than it is about me making money. Seriously, i'm being honest. Heck, i'd love to have one of these, even if only to keep my now-retired San Andreas company.

Anyways, this is where things stand. Right now i'm looking for an intact crown to use as a blueprint. If anyone is kind enough to help out here i'm sure it's greatly appreciated by owners abroad.

PATIA for all/any help.

 

[DeeEight]

C'mon... do it in 2014T6... it'd be stronger ! Mine cracked its headtube, as have most others on here. The rear crown assembly is a lesser problem for them.

 

[laffeaux]

Are the crown really an issue?

I thought that the frame tubes failed long before the crowns ever had a chance to give out. However, if you have people desperately seeking crowns, I have a perfectly good one attached to a still working bike.

 

[DeeEight]

The guy he mentioned is the first i've heard of on here in 8 years of the rear crown failing. There's another FS-DH frame owner a mile from me and he's cracked his headtube also.

 

[nutallabrot]

I've only seen one FS frame with a broken rear crown and that was a really beat up frame on ebay. As said before, the head tube is more of an issue. I've got 4 replacement crowns (2 Manitou, 2 Marin) of bikes where the frame cracked first.

If there are people out there that need a replacement crown your project is of course appreciated. But given the number of broken frames it shouldn't be so hard to find an original rear crown.

 

[AndrewTO]

I was under the impression from posters here on MTBR that this was a problem (the rear crown breakage). I never said more or less than the tubing, but ..... (shrug)

Okay, scrap that idea. If it's not that bad then i'm not going to worry about it. Less for me to possibly be liable for (don't ask).


Dee - the guy I mentioned doesn't even have the same frame i'm talking about. I was never aware that frame type had any suspension breakage issues (could very easily be wrong here), but that thread is about making a conversion mount - something entirely different that this thread.