[FactoryCostcoDH]

I just recently got this awesome little program called Linkage on my computer, and so far after dinking around a bit, I've come up with two frames. I'm open for suggestions, advice, or commentary as I am eagerly trying to learn more and more about frame design. Just as a side note, I designed the frames around my riding style, so they might seem very unconventional to some.


Anyways, here's the FR/DH rig with a single crown (It's labled as a MC 9.5 in the graphs) :

(Unsagged)

(Sagged)

(Bottomed)

And this is the Experimental DH rig on the border of too much travel (~11" rear / 10" front / 14x6 shock)

(Unsagged)

(Sagged)

Let me know what you think

 

[ridefast]

hmmm....definitely interesting. the top isnt too confusing, but the bottom is a bit difficult to see it working well

 

[demo 9]

is that frame possible to make. is that fake shock 9.5 by 3?

 

[karpi]

good designs! My only sugestion and question, why did you mount the bb on the swingarm on your long travel frame? The only good thing about this, is chain wont stretch, but other than that, what other advantages does it present?

 

[greenblinker104]

damn 17.6in rear stays on a fr bike...that is long

through a dc fork on the first frame and that would make a better dh race bike imo with the long stays and a 66 degree up front

18.5in chainstays wow that is huge

i like the top frame way more. the bottom frame reminds of an ecd a little bit

 

[karpi]

the other problem I see, your first frame, when at bottom out, the rear wheel will most defenetly touch your saddle

 

[FactoryCostcoDH]

Well I guess it would be possible to make, but I don't have the resources. Also due to the limited amount of time I had to work with (homework), both frames could be improved (the best I could do was fit a 9x3 on the FR bike)

Once again, with the time restriction, I couldn't find a good mounting position for the bottom bracket on the second frame without producing a ridiculous amount of chain growth or length. And as far as advantages, I've heard that it helps with pedaling efficiency as well as keeping your weight more towards the rear of the bike where it needs to be.

The reason I mounted the single crown fork on the first bike was that I had planned to make both a FR and DH bike with the same frame, but once again I only had time to finish the FR version because I would have had to redraw the front end of the frame to accommodate an 8" travel fork and I didn't have the time. The chainstays are fairly long for two reasons. One reason being that I had a hard time trying to fit the linkage properly while still maintaing the right force curves with the smaller space to work with, and the other reason that I intended the bike to be more of an "extreme FR" bike on which you would be doing more of the huge gaps/drops/etc rather than north shore style trails. Notice the extreme progression towards the last 2" of travel and the low shock placement as well. I intended the bike to be low, stable, and plenty stiff when you need it most. The slack HA and rearward axle paths are more just my own personal preferance.

 

[FactoryCostcoDH]

Yeah I just noticed that. That can be fixed though. These are somewhat my rough drafts

 

[FactoryCostcoDH]

Messed around with paint this morning:

 

[khoolhandz]

Well I guess it would be possible to make, but I don't have the resources. Also due to the limited amount of time I had to work with (homework), both frames could be improved (the best I could do was fit a 9x3 on the FR bike)

Once again, with the time restriction, I couldn't find a good mounting position for the bottom bracket on the second frame without producing a ridiculous amount of chain growth or length. And as far as advantages, I've heard that it helps with pedaling efficiency as well as keeping your weight more towards the rear of the bike where it needs to be.

The reason I mounted the single crown fork on the first bike was that I had planned to make both a FR and DH bike with the same frame, but once again I only had time to finish the FR version because I would have had to redraw the front end of the frame to accommodate an 8" travel fork and I didn't have the time. The chainstays are fairly long for two reasons. One reason being that I had a hard time trying to fit the linkage properly while still maintaing the right force curves with the smaller space to work with, and the other reason that I intended the bike to be more of an "extreme FR" bike on which you would be doing more of the huge gaps/drops/etc rather than north shore style trails. Notice the extreme progression towards the last 2" of travel and the low shock placement as well. I intended the bike to be low, stable, and plenty stiff when you need it most. The slack HA and rearward axle paths are more just my own personal preferance.

The swingarm-mounted bottom bracket will not work, specially on this very low leverage frame design. The weight of the rider will counteract the swingarm action and because the leverage ratio is so low. Specially if you wanted to make this frame for freeride/hucking, you'd want the suspension (not the swingarm) to fully absorb your weight on impact.

 

[fellow pinner]

The first one looks just like the session ten.

 

[NY_Star]

That first one Looks like the new Tomac primer 220

 

[Dr. Ill]

Where'd you get that program?

 

[cheetaprowlerDH]

Search "bike linkage program" on google. It should show up first on the list. The demo version is free but you can't save any of your designs. The full version however is only $25.

 

[FactoryCostcoDH]

The swingarm-mounted bottom bracket will not work, specially on this very low leverage frame design. The weight of the rider will counteract the swingarm action and because the leverage ratio is so low. Specially if you wanted to make this frame for freeride/hucking, you'd want the suspension (not the swingarm) to fully absorb your weight on impact.

Thanks for the advice, I'm still learning as I go. Keep in mind that I'm only 17 and just recently got interested in the science behind how frames work. As of now, I'm just learning by trial and error.

 

[w00dy]

A couple things I think you should design for (if you're doing it from scratch):
Try to keep the shock vertical, You'll notice that motorcycles always have the shock vertical. It's the same premise as an inverted fork. gravity helps keep lube where it needs to be and push dirt off the sliding surfaces.
Simplicity is golden. Fewer linkages=fewer weak spots=less weight=mo' better.

 

[dante]

A couple things I think you should design for (if you're doing it from scratch):
Try to keep the shock vertical, You'll notice that motorcycles always have the shock vertical. It's the same premise as an inverted fork. gravity helps keep lube where it needs to be and push dirt off the sliding surfaces.

lthumbsdown:

 

[ÆX]

lthumbsdown:

sound like a good idea to me?

whats your reasoning?

 

[MobileChernobyl]

Yea it sounds good to me as well, while not always feasible, the logic is there.

I'm not sure if you've already bought the full version or not, but you dont need to if your trying to push from linkage design to 3d modeled in solidworks or whatnot. Just keep a spreadsheet of all the important editing points and do a 2d cadd sketch up of that for your 3d model to be based off of. Works pretty well and its nice to have linkage figure out your leverage ratios ahead of time so you dont end up with a ****ty design that looks cool. But after that the frame can still look good in numbers and ride like poo, so push it to production, try the 1st model - its a pretty cool design albeit prolly a little trickier than you think to make.

 

[FactoryCostcoDH]

Here's another one. I'm starting to realize more similarities/common strengths between well proven bikes, which has in turn changed my concept of leverage completely. The whole concept of virtual pivots is starting to make a lot more sense as well. Anyways this is my first attempt at a VPP bike, and it somewhat looks like a mix between a sunday and a v10.


Unsagged

Sagged

Half Travel

3/4 Travel

Bottomed

Performance and complexity don't always go hand-in-hand, but I thought I'd try

 

[Dr. Ill]

I've been fooling around with this program and it is awesome....
There are a lot of moving pieces on ur bike but the relsults look good. This is a lot of fun.

 

[Dr. Ill]

What's the optimal setting for chain growth? 0?

 

[SteezyWeezy]

ya as little chain growth as possible

 

[FactoryCostcoDH]

zero is a good number if you want to be in the neutral zone. but I personally would almost want a little bit (not too much) of chain extension beacause it helps with pedaling. Also, a slight chain extension can rotate the cranks back a few degrees keeping slightly more pressure to your feet under compression, which could help with people who choose to use platform pedals. Anywhere around 1" or less should be fine

 

[cheetaprowlerDH]

alot of times, chain growth will cost you $$$...
with alot of chain growth, your derailleur extends during the compression of the suspension. if you are as unluck as i have been quite a considerable amount of times, that chain extension will drag your derailleur into the spokes, which will either rip it straight off or break a few spokes...

not to mention positive or negative pedal kickback... (this keyboard sucks, i dont want to go in depth...)
FactoryCostcoDH knows where i'm coming from...

 

[FactoryCostcoDH]

Couple different color schemes:

 

[AfroJack]

When using linkage you should take into account a lot of the models included in the program are not the exact dimensions of the bikes. The program will give you a general idea of how the suspension curves look, but they are by no means the real deal. Most of the designs are from someone just getting a caliper out and making rough guesses at pivot locations. Your designs look interesing but the last one you went a little crazy on the linkage, you might want to consider the horizontal space (between your cranks) you have to work with and think about how you are going to fit all those linkages in there. But keep it up, designing and building frames is a lot of fun.

 

[FactoryCostcoDH]

Yeah I've noticed some of the bikes being different than they actually are, but it does give a rough repsresentation.

I just wanted to try a more complex design, just to see how things worked out. It is nice thought because it allows you to tune the leverage curves more precisely, as well as the whole virtual pivot idea.

The bottom two links don't need to overlap, so I could just use a slightly wider BB and there would be plenty of room

 

[Demomonkey]

I like the first design because its the least complicated. Impressive efforts nonetheless.

My advice is to keep it simple.

 

[cheetaprowlerDH]

i still need to learn how to draw new polygons that connect links and such, but right now ive been working with the personal version and improving(in my eyes) production bikes... once i get some sick ones, i'll post 'em up... unless i find out how to make it work with the snapshots of my own 2D "paint" designed bikes...

 

[- seb]

Fascinating program, comparing the new-type DHi to my old-type one at the moment. My old one appears better in most respects (though it's all arguable isn't it, but it has a more rearward axle path and less chain growth) but as someone mentioned they're not necessarily 100% accurate to the actual bikes.

 

[karpi]

It's fun to see what you can do with so many linkages, the problem is, the more linkages you have, the more the weight, more maintance, and the more moving mass. Like someone said, keep it simple and it should work flawlessly. I also liked your first design the most. It seemed to work really nicely and had a crazy low center of gravity.

 

[SPDR]

I've found it's a little frustrating so far - I want to try incremental modifications to things but if you change one thing; others change. You can't set parts to a size then move them around to get the best fit/change the leverage curve/see what happens to the instantaneous centre etc.

Can I set what parameters/measurements can change while having ones that won't? IE fixed shock length/ head angle/ BB height/ chainstay length/ with movable pivot positions?

Could also do with a DXF input/output option too but maybe all that's in the PRO version . . .

 

[FactoryCostcoDH]

Here's a few short travel bikes. One's a mini DH and the other's a slopestyle