Author Topic: How to design a new suspension linkage (Read 19686 times)

Hawaiiysr · « **Reply #15 on:** February 04, 2014, 08:40:13 AM »

Add me to the list. I ditched my air box long ago. if a custom intake is the price to pay for a LT rear linkage I'm game all day.

rablack21 · « **Reply #16 on:** February 04, 2014, 10:37:36 AM »

Quote from: andy@maultechatv;24544

Just checking interest here to see if anyone would be interested in seeing how we go about designing a new suspension linkage? I'm planning on designing tomorrow if we get a big snow like they're talking (no customers stopping by). I figured I would use the GoPro and record the process if there's enough interest. And no this won't be for the 250R, we already tried that and there's too many things that won't let it work on a stock frame!

Is this a joke? Of course we want to see the video!

Quote from: andy@maultechatv;24645

The problem we found is not the linkage it's the clearance from the swingarm to the airbox and exhaust. You will destroy the stock airbox or a stock exhaust with a suspension that has the correct up travel of the rear wheels. I don't want to make a new linkage and then get calls all the time because they destroyed their airbox that you probably can't buy anymore. The frame is still 3" off the ground when clearance issues are a problem!

I understand the problem. However, like several others mentioned, we would love to see a solution for this even if it meant ditching the air box or going with a 450r swinger setup. I think there is some real potential to keeping our R's alive by be able to use a 450r swinger and special linkage setup (similar to 450r linkage). You could make the linkage exclusively and make lots of money off all of us happy customers!

rk88r · « **Reply #17 on:** February 04, 2014, 10:47:45 AM »

Yfz linkage appears to be similar to cr500. Modifying the frame and more would be worth it to have the option of swapping in readily available components.

05450r · « **Reply #18 on:** February 04, 2014, 10:53:24 AM »

Correct, but yfz uses a really long rear shock. There was a guy on atvriders that started to do this swap and bailed. Not sure why, I will try to find the link.
http://www.atvriders.com/vbb/showthread.php?423445-My-MX-National-bike-build-thread

troybilt · « **Reply #19 on:** February 04, 2014, 11:13:49 AM »

The upper shock mount, linkage, lower link mount, swingarm length, swing arm linkage mount, Counter sprocket location relative to the swingarm pivot, angle of swingarm relative to chain (anti-squat), angle of the rear shock thru the travel, ride height, frame clearance, etc... are all are geometric factors, just slapping in a another swing arm or linkage from another bike is not always a good idea. The entire system must be accounted for when experimenting with this. It is possible to design a new link or adopt a link for stock frames, but you need to ask what problems are you trying to fix? Too much progression, not enough progression, traction, up travel, down travel, etc... What works for one is not always universal, just my couple of cents...

Regarding the original topics I would like to see the videos myself, I love the technical videos!

05450r · « **Reply #20 on:** February 04, 2014, 11:22:57 AM »

Exactly Troy!! There was another thread here somewhere when we dug into this subject a little deaper.

05450r · « **Reply #21 on:** February 04, 2014, 11:30:22 AM »

http://trx250r.org/showthread.php?1760-Cr500-link

troybilt · « **Reply #22 on:** February 04, 2014, 12:09:53 PM »

Suspension geoemetry is very interesting to me, I'm a student of the game. The nerd in me actually spent the time over my Christmas break to solve the 4 bar linkage equations out by hand for all types of suspensions CR links, Walsh/JB style links, Stock 450, No Links, etc... I then created a spreadsheet/macro/solver to calculate leverage ratio and Force ratio curves to compare each design and plot the curves, and then of course be able to adjust parameters to ultimately design my own links, swingarms, etc.... This is just one part of the overall picture though, but it starts to paint a picture of what's going on mathematically for each linkage. If I remember I'll try and post some pics.

I also did some investigating on "infintely adjustable progressive spring stacks", basically looked at wave spring stacks, vs. common coil springs. The technology just isn't there yet, but the potential is interesting, I think. The idea of having even more spring rates vs. 2, 3, 4, 5, etc..., basically takes the linkage out of the equation and you can design progressive spring rates for any type of riding, at least from a spring standpoint, plus they are super light! Valving though is another topic.

Here is an example of a wave spring, you can stack these as thin as 1 wave spring, to build up a "stack" with different rates... http://www.smalley.com/
One major flaw though with this idea, is wave springs don't have the duty cycles that coil springs do so they can take a "set" quickly and then you're done. So technology would have to improve. Interesting though to think about.

I think to determine what is "better" is very subjective. Like Laz mentioned validation and testing to develop a "system" together, i.e. linkage and shock is what it takes.

jcs003 · « **Reply #23 on:** February 04, 2014, 12:43:47 PM »

here is some food for thought:

http://www.promecha.com.au/leverage_linkages.htm

http://www.promecha.com.au/springs_advanced.htm

john

Langbolt · « **Reply #24 on:** February 04, 2014, 01:01:52 PM »

^ x2

andy@maultechatv · « **Reply #25 on:** February 04, 2014, 07:49:04 PM »

Quote from: troybilt;24673

The upper shock mount, linkage, lower link mount, swingarm length, swing arm linkage mount, Counter sprocket location relative to the swingarm pivot, angle of swingarm relative to chain (anti-squat), angle of the rear shock thru the travel, ride height, frame clearance, etc... are all are geometric factors, just slapping in a another swing arm or linkage from another bike is not always a good idea. The entire system must be accounted for when experimenting with this. It is possible to design a new link or adopt a link for stock frames, but you need to ask what problems are you trying to fix? Too much progression, not enough progression, traction, up travel, down travel, etc... What works for one is not always universal, just my couple of cents...

Regarding the original topics I would like to see the videos myself, I love the technical videos!

I actually addressed some of these things in my video today. Hope this gets people thinking too.

rk88r · « **Reply #26 on:** February 05, 2014, 07:53:01 AM »

Ski Doo has a linkage set up in their new sleds that separate the spring and the shock and have different linkage ratios in each. Just some food for thought.

JoePA · « **Reply #27 on:** February 05, 2014, 09:32:43 AM »

Not to get off topic but being 250r owners our choice of parts is limited daily. The 450 conversion going to have to become a reality at some point in time if we are to survive in the future. Aftermarket swingarms are expensive and hard to come by where the 450r stuff is cheap and readily available. Nothing is perfect but I'm sure some kind of linkage can be made to make it work well.

Looking forward to the video Andy.

andy@maultechatv · « **Reply #28 on:** February 06, 2014, 07:17:16 AM »

drum roll please. LOL Enjoy. I'm going to post this also at the top of this thread too so anyone clicking on this doesn't have to scroll through to find it.

[video=youtube_share;SW9G0o-Nytk]http://youtu.be/SW9G0o-Nytk[/video]

05450r · « **Reply #29 on:** February 06, 2014, 10:42:06 AM »

Very cool Andy, thank you for taking the time to make videos for us!!