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Posted: May 14, 2021 at 23:16 Quote
Hugh is one of the few good kinematics designers in the industry. The one point on which we disagree is stability vs. instability of a decreasing anti-squat curve. Other than that, definitely listen to him! If you get deep enough into this to want to discuss stability of anti-squat curves, I'll be happy to oblige.

Posted: May 14, 2021 at 23:19 Quote
R-M-R wrote:
Hugh is one of the few good kinematics designers in the industry. The one point on which we disagree is stability vs. instability of a decreasing anti-squat curve. Other than that, definitely listen to him! If you get deep enough into this to want to discuss stability of anti-squat curves, I'll be happy to oblige.

Definetly, but right now I couldn't tell you what any of that^ meant lol I would guess anti-squat has something to do with how much the suspension lowers with the weight of the rider as opposed to the objects on the trail? My eyes are burning...

Posted: May 14, 2021 at 23:28 Quote
I'm afraid that's not it at all.

Squat, in this context, is the amount the suspension compresses due to either braking forces ("brake squat", which is the same as "brake anti-rise") or pedaling forces ("pedaling anti-squat", usually just called "anti-squat").

Pedaling anti-squat uses the chain tension to squeeze the suspension and reduce the amount the rear compresses due to acceleration. Think of how you do a wheelie: pedal hard and shift your weight back. A milder version of that happens during normal pedaling, but it's not enough to get the front wheel off the ground. A frame with rear suspension allows the frame do "pop a wheelie" internally, by rotating around the pivot point. Anti-squat uses chain tension to counteract this force and prevent this internal wheelie, keeping the chassis stable.

Posted: May 14, 2021 at 23:33 Quote
R-M-R wrote:
I'm afraid that's not it at all.

Squat, in this context, is the amount the suspension compresses due to either braking forces ("brake squat", which is the same as "brake anti-rise") or pedaling forces ("pedaling anti-squat", usually just called "anti-squat").

Pedaling anti-squat uses the chain tension to squeeze the suspension and reduce the amount the rear compresses due to acceleration. Think of how you do a wheelie: pedal hard and shift your weight back. A milder version of that happens during normal pedaling, but it's not enough to get the front wheel off the ground. A frame with rear suspension allows the frame do "pop a wheelie" internally, by rotating around the pivot point. Anti-squat uses chain tension to counteract this force and prevent this internal wheelie, keeping the chassis stable.

Ah, so it is a problem of pedalling effeceincy? (pretty sure I spelled at least one of those wrong) it almost sounds like one of those ethereal problems we know exist but only someone who has been riding a long time would notice. Not trying to bash the idea, I just wouldn't notice something like that unless someone pointed it out to me.

Posted: May 14, 2021 at 23:37 Quote
Pedaling and braking. Separate properties, though. People mostly discuss, and mostly notice, pedaling anti-squat. Brake squat (AKA brake anti-rise) is the kinematic parameter I worry about least when designing a bike.

Yes, pedaling anti-squat is related to efficiency. It's what gives one bike a "squishy" pedaling feel, another bike a "firm" pedaling feel, determines the amount of pedal kickback, and is related to the axle path. I'm sure you would notice these things if you were guided on what to look for.

Posted: May 14, 2021 at 23:40 Quote
R-M-R wrote:
Pedaling and braking. Separate properties, though, and people mostly discuss pedaling anti-squat.

Yes, pedaling anti-squat is related to efficiency. It's what gives one bike a "squishy" pedaling feel, another bike a "firm" pedaling feel, determines the amount of pedal kickback, and is related to the axle path. I'm sure you would notice these things if you were guided on what you're looking for.

Definetly felt the squishy pedalling feel.

The first 'real' mountain bike I ever rode was at the United bicycle Institute in Ashland, Oregon. There was an older mechainc their who was taking the same class I was who is a foes fan and had his suspension super-skwishy.

I don't know if you have ever been to a trampoline park but it felt like stepping onto one of those trampolines and sinking six inches.

Posted: May 14, 2021 at 23:46 Quote
I know what you're saying, though some of what you felt may not have been due to anti-squat.

The Foes DHS (assuming that's what you rode) does have somewhat low pedaling anti-squat, so that's not helping the pedaling efficiency. It also has a lot of travel, so even if the chain tension balances the "wheelie" forces, vertical inputs from the rider's pedaling style won't be balanced. If you were standing and sprinting with a sloppy motion like you were trying to climb a Stairmaster, the bike has a lot of soft suspension that you would've been bouncing around on.

Another factor is low-speed compression and low-speed rebound damping. These are properties of how the shock has been tuned for a given bike, and are effective tools to minimize bobbing due to the rider's body movements.

Posted: May 14, 2021 at 23:49 Quote
R-M-R wrote:
I know what you're saying, though some of what you felt may not have been due to anti-squat.

The Foes DHS (assuming that's what you rode) does have somewhat low pedaling anti-squat, so that's definitely not helping the pedaling efficiency. It also has a lot of travel, so even if the chain tension balances the "wheelie" forces, vertical inputs from the rider's pedaling style won't be balanced. If you were standing and sprinting with a sloppy motion like you were trying to climb a Stairmaster, the bike has a lot of soft suspension that you would've been bouncing around on.

Another factor is low-speed compression and low-speed rebound damping. These are properties of how the shock has been tuned for a given bike, and are effective tools to minimize bobbing due to the rider's body movements.

Theres something I know about. I have to scram and o catch some Z's, but will definetly read the website and those videos. I will have to go read the article you sent me again on frame material, too. Thanks!

Posted: May 14, 2021 at 23:59 Quote
Enjoy, and let us know if you have specific questions.

O+
Posted: May 15, 2021 at 12:47 Quote
rosemarywheel wrote:
I am not sure if this is the best place to ask this either, but I cannot for the life of me find out how fork stanchions are made. Does anyone have any info on this? I can make educated guesses but would love to find a video or article. Maybe I need a different search engine.

They are extruded aluminum tubes that get threaded and a coating process applied to them.

Posted: May 15, 2021 at 16:19 Quote
NorCalNomad wrote:
rosemarywheel wrote:
I am not sure if this is the best place to ask this either, but I cannot for the life of me find out how fork stanchions are made. Does anyone have any info on this? I can make educated guesses but would love to find a video or article. Maybe I need a different search engine.

They are extruded aluminum tubes that get threaded and a coating process applied to them.

Well, ...Yeah. I hope I don't sound too much of an @$$ but I knew that. I know enough about manufacturing to guess that much. I am looking for something a bitmore specific.

What does the machine look like? is it cold or hot when it is extruded? how is it cooled without any bending or warping? Tolerances? is it polished after the extruding? heat treat or no? thickness of walls? are they he butted tubes? what does the extursion part of the machine look like and function? (the jaws)

Or better yet, just finding a place to make 'em for me would be grand. Avalanche suspension was no help at all, I am going to try Fox, DVO and RS next.

Posted: May 15, 2021 at 22:55 Quote
What exactly is your goal? If you want to extrude your own profile then you're better ready to invest 10 grand in tooling.
I also think they are ground after extruding to get a better surface finish and tolerances. They also might be tapered in the crown so in that case it will become quite complicated. But for a set of one ofs you can do some stupid machining that wouldn't be economically viable for large scale.

Posted: May 15, 2021 at 23:08 Quote
SleepingAwake wrote:
What exactly is your goal? If you want to extrude your own profile then you're better ready to invest 10 grand in tooling.
I also think they are ground after extruding to get a better surface finish and tolerances. They also might be tapered in the crown so in that case it will become quite complicated. But for a set of one ofs you can do some stupid machining that wouldn't be economically viable for large scale.

I am going to make a chassis for a yet-to-be-created set of lowers and bridge machined by myself. I do have to wait until I can get back into the shop at school to use the lovely CNC lathe but I have Solidworks so I may as well design now.

There are sets of older Fox Fork Stanchions (New Old Stock) here on PinkBike so I may just buy those. I was just hoping to find an option of acquiring more if the guy on PB doesn't have more.

https://www.pinkbike.com/buysell/2672468/

I want something that is bombproof and the oldschool look like a Monster T (and the quality, of course) but with much more modern dampening. I will be throwing in either a Avalanche Damper (they do sell the damper as far back as 2005 for the Fox 40 stanchions I am enquiring about) and I can use Fox o-rings and seals. The reason for choosing (besides the bombproofness of the Monster) design is because the bridge and lowers are machined separately, instead of one piece. Once I found out about that, it became much easier in my mind to potentially manufacture one.

If it works out, and people like them, I may make more at peeps request. And I know of a guy who could paint them for me... https://www.maderad.com/
Or I can get custom stickers made. But paint is preferable.

i basically didn't want to depend on NOS Fox stanchions in case I ran out. I can of course get them elswhere, but it was the principal that counts. And knowing exactly how something is made somehow helps me design the rest even if I have no intention of making that part... but I cannot find any info on it Frown

And I am after Anodized stanchions only, no nickel plating.

Posted: May 15, 2021 at 23:31 Quote
Bravo for your commitment, but that's now how I would recommend doing it.

Even fork "manufacturers" don't exactly make their own. In most cases, they're just a standard OD & ID, maybe with a custom surface finish. Just go to a small motorcycle fork manufacturer and ask to purchase their stanchions or buy a few damaged Fox 40s and scavenge their stanchions.

If you get your own custom finish (try really hard to avoid it, but if you insist ...), it's the bushing vendor you want to talk to about tolerances.

Are you aware the Super Monster was just Marzocchi's moto trials fork with one of the two damper cartridges removed? Just do that. Buy whatever the MOQ (minimum order quantity) may be to get OE pricing - I'm guessing 50ish - make a tiny modification, and there you go: Super Monster v2.0.

O+
Posted: May 15, 2021 at 23:56 Quote
Didn't one of the aftermarket suspension mod companies make replacement stanchions for Boxxers / 40s? Thought it was Fast, can't find any evidence on their website though.


 


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