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Posted: Apr 20, 2021 at 12:51 Quote
I've been working on the leading-link design. Here's the question, and I know that this is personal preference, but what are ideal suspension numbers? In an ideal world, how much anti-rise, anti-squat, and progression would a bike have?

Right now the fork has 17% of progression, mounting holes for 82% to 96% anti-rise at sag (need to make some graphs of the curves). How are these numbers?

Posted: Apr 20, 2021 at 13:48 Quote
If you've definitely done the calculations correctly, the motion ratio sounds reasonable. I recommend less anti-dive, if it's anti-dive you're asking about.

Could you post an image so we can help verify your numbers?

Posted: Apr 20, 2021 at 14:24 Quote
Hi, My top tube broke. The crack leads from the bottom of the tube. Does anyone have an idea why? I don't think this place is highly stressed. I also did a quick simulation that confirmed it. Thanks
TT 31.7 0.8-0.6-0.8 Dedacciai ZERO UNO
DT 38.1 0.9 4130

Posted: Apr 20, 2021 at 14:45 Quote
To my knowledge this almost always happens because the joint got too hot and it compromised the steel. You might want to check with an expert to verify.

Posted: Apr 20, 2021 at 21:05 Quote
zdenny55,

Does your analysis account for the different wall thicknesses and the down-tube gusset?

Posted: Apr 21, 2021 at 0:40 Quote
Top tip: if your simulation shows something is fine but in the real world it breaks, the simulation is wrong.

Source: been there, done that (and boy was it not cheap) Frown

Posted: Apr 21, 2021 at 10:14 Quote
Yo guys, I had some time off this last week and a half due to a destroyed collarbone Frown

I have a mac and couldn't use bikechecker, nor did I want to go buy parallels or some equivalent software to fake my mac into a windows. I went ahead and designed the linkage and pivot points in excel/Fusion360 using a lot more mental effort than was likely necessary. Could I give one of you guys some of the pivot locations and you'd be able to double check my math/provide feedback on the general design?

High Single Pivot w/ Linkage driven shock


Posted: Apr 21, 2021 at 12:15 Quote
EarninTurns wrote:
Yo guys, I had some time off this last week and a half due to a destroyed collarbone Frown

I have a mac and couldn't use bikechecker, nor did I want to go buy parallels or some equivalent software to fake my mac into a windows. I went ahead and designed the linkage and pivot points in excel/Fusion360 using a lot more mental effort than was likely necessary. Could I give one of you guys some of the pivot locations and you'd be able to double check my math/provide feedback on the general design?

High Single Pivot w/ Linkage driven shock


Hey, another person that did it in excel! Props to you good sir.

I'd be happy to compare using my program.

Posted: Apr 21, 2021 at 15:27 Quote
EarninTurns wrote:
Could I give one of you guys some of the pivot locations and you'd be able to double check my math/provide feedback on the general design?

That's my job, so yes. Also, that's my job, so I can't give it away for free, but it could take less than an hour.

Posted: Apr 21, 2021 at 18:03 Quote
[[/Quote]

Hey, another person that did it in excel! Props to you good sir.

I'd be happy to compare using my program.[/Quote]

Turns out this Mac and Cheesy POS can't print to pdf or I can't figure it out. I started adding points and realized I needed to give more and more information. here's a screenshot from Fusion360 of my drawing.

Gearbox
High pivot
Linkage driven single pivot suspension
143*ish/160
Moderate geo in comparison to a lot of other bikes - 5'10 (178cm for you non Freedom Unit Users)


Posted: Apr 21, 2021 at 20:49 Quote
@EarninTurns

So I threw it into CAD to work backwards to get some dimensions, so this is a rough approximation. Also, because I'm working on the solver right now, I couldn't use it to perfectly reverse engineer your result. I also had to make a couple of assumptions about the bike, but they were fairly obvious.


This is the linkage plot showing your anti-rise and anti-squat lines with an axle-member mounted idler. I assumed your idler was a 12T, and mounted to the swing-arm in-line with the axle and main pivot.


Looks like you used a CG y+ of ~820mm. So your anti-rise and leverage ratio curves look to be correct (once again, the LR curve is off because I didn't run the solver to get it perfect to what you claimed it should be).

As for your chain-growth calculation, the values I'm getting are a little bit off, but that could be due to the rough dimensioning.


I went ahead and even assumed that the idler was mounted to the frame instead.


So while the pedal-kickback increased because of the increased chain-growth, I'm seeing around 30mm on a 51T cog. Not sure what size cassette your bike is supposed to have.

Posted: Apr 22, 2021 at 6:41 Quote
Fueniker wrote:
@EarninTurns


So while the pedal-kickback increased because of the increased chain-growth, I'm seeing around 30mm on a 51T cog. Not sure what size cassette your bike is supposed to have.

Wow, your homemade software is impressive! Thanks for taking the time to check my work!

CG is 780mm directly above the BB. I was talking with TrailPov youtube guy and he was explaining that's what he uses for all his measurements.

I'm planning on a gearbox so no cassette. It'd be a 'single speed' for purposes of our analysis. The Pinion chain tensioner has 140mm of chain growth capabilities so so long as I'm under that I *should* be ok - emails to pinion on that when I get a bit more confident in my math model. I'll double check my measurements there.

Posted: Apr 22, 2021 at 7:16 Quote
EarninTurns wrote:
Wow, your homemade software is impressive! Thanks for taking the time to check my work!

Thanks Big Grin
And no problem, glad to help!

EarninTurns wrote:
I'm planning on a gearbox so no cassette.

Ah, well it's good to know that my reading comprehensions skills have not improved since school lol

Posted: Apr 22, 2021 at 11:43 Quote
this is clearly the future!



 
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