Time to make a frame =)

MobileChernobyl · Jul 9, 2008

Haha, you have the half of the "bike frame design/making" that most people want but never get. If you have a sound background in math, and a general knowledge of physics and all its doings, you can most likely design yourself a simple single pivot with the program bikechecker (used to be, or still is called linkage 2.5) and nice big sheet of paper. Some woodworking skills are handy for throwing together a quick jig, but since your in a metal shop, you could make a kick ass jig out of 1/4" sheet alu cut-offs. Search around, this forums got a **** load of recent threads on homemade DH/FR frames.

jeremyb · Jul 10, 2008

Get linkage and have a play, its worth buying

norbar · Jul 10, 2008

Blank if you ask for geo ideas than please first post what is the intended use of the frame cuz for now it's only guesing.

BTW. If you go for high pivot maybe look at balfa,appalache empire and new corsair designs - High pivot with rearward axle move and idler pulley. Even in demo of linkage you should see a lot about those bikes.

ridefast · Jul 10, 2008

damnit i guess pinkbike is down again

LMC · Jul 10, 2008

'obtain' a copy of solidworks or solidedge..

ive used solid edge for a number of years and it took me about 1 week when i got it at first to learn enough to create a basic frame. there are tutorials you can work through which will show you what u need to know..

pm me for a copy

EDIT: also get the personal version of linkage, as mentioned above. it costs buttons and will come in handy, for example if you want a high, single pivot with a slightly rising leverage ratio, look at the balfa, copy the coordinates of the main pivot, and shock mounts, plot them in your CAD software and scale them up/down to match your chosen shock length

sperkins · Jul 10, 2008

LMC said:
'obtain' a copy of solidworks or solidedge..

ive used solid edge for a number of years and it took me about 1 week when i got it at first to learn enough to create a basic frame. there are tutorials you can work through which will show you what u need to know..

pm me for a copy

EDIT: also get the personal version of linkage, as mentioned above. it costs buttons and will come in handy, for example if you want a high, single pivot with a slightly rising leverage ratio, look at the balfa, copy the coordinates of the main pivot, and shock mounts, plot them in your CAD software and scale them up/down to match your chosen shock length

yeah definitely get a copy of solidworks that should help you get started.

MobileChernobyl · Jul 10, 2008

Rhyno3D is freeware i believe, and its a 3d Cad program, i dunno if anything listed above is "free"

The cheapest you can get solidworks legaly is the student version for $80-$90 and it expires in a year (there may be patch files to get rid of the expiration code). However if you know someone who knows the intarweb well, get him to make a full suit version of solidworks appear on your computer if you catch my drift. That way you get cosmosworks the full version, where you can test (albiet not 100% accurately) assemblys.

Edit:: Now i see the quotes around obtain LMC haha, yea 'obtain' a copy of solidworks if you can. its hella easy and fun to use after a week of learning.

Stray_cat · Jul 10, 2008

I'd avoid the 3D modeling programs, it's just not needed, and they're expensive. 2D will be faster as well. I use 3D if I'm designing a new dropout that's complex, or someother CNC'd bit. But when it comes to dealing with frame manufacturers all my frame drawings are done in 2D.

Edit: While I'm all for free stuff 'Obtaining' solidworks is the equivilant of stealing $5000. That's a fellon brotha. Cosmos...$15,000.

Good luck man. Post some progress pics when your up and running.

MobileChernobyl · Jul 10, 2008

Stray_cat said:
Edit: While I'm all for free stuff 'Obtaining' solidworks is the equivilant of stealing $5000. That's a fellon brotha. Cosmos...$15,000.

cry me a river :nopity:

I'm the least of your worries out there lol. Your prices are a little exagerated as well.

BJ- · Jul 11, 2008

Stray_cat said:
I'd avoid the 3D modeling programs, it's just not needed, and they're expensive. 2D will be faster as well. I use 3D if I'm designing a new dropout that's complex, or someother CNC'd bit. But when it comes to dealing with frame manufacturers all my frame drawings are done in 2D.

Edit: While I'm all for free stuff 'Obtaining' solidworks is the equivilant of stealing $5000. That's a fellon brotha. Cosmos...$15,000.

Good luck man. Post some progress pics when your up and running.

What 2D modeling programs would you reccomend?

Lollapalooza · Jul 11, 2008

Download the trial of Rhinocerous. It's free and pretty easy to work in 2d.

ChrisKring · Jul 11, 2008

If the guy doesn't want to learn cad, why not just draw it out full scale on paper. He could trace a few bikes that he likes and overlay them to see what the differences are. Then, he can design up the frame full scal on paper. I am assuming that he knows how to develop the joints to fit if he is a fabricator. You can do it with math, cad, paper or some simple fabricating tools.

We (my paying employer) do basically the same thing in CAD all the time when reverse engineering competitor products to develop the physics models on how things work. The funny thing is that sometimes when you deep dive into competitor products you sometimes find out why their products are failing and see "the light" on how easily they could fix it. Then if your really slick, you can lock down the IP on the fix.

Rick205 · Jul 11, 2008

Go to the solidworks website, you can download the student edition for free and it wont cost you a penny, just search google for a university code for solidworks student... i used my own as i was at uni.

It does expire after a year correct, and it has limited function in that you cant perform fea on it (as the level of cosmos that comes with it is impared) and you cant save as iges or other such files so no exporting the files to cnc or other company for further development.

Rick

no skid marks · Jul 11, 2008

What will work on a Mac?

EB-Mitchell · Jul 11, 2008

Hi. I have been working on a DH frame for about 2 and a half years now... It is very difficult to get things right. My suggestion is to download the try out version of cadopia IntelliCAD for 2d and then the trail version of rhino to convert it to 3d. It would also be best to take a short course on cad at your local school or something. Here is my final design (I am in the process of mitering the tubes and machining).

MobileChernobyl · Jul 11, 2008

Rick205 said:
just search google for a university code for solidworks student... i used my own as i was at uni.

Thats a clever idea, I would suggest Rick's suggestion over the mention of "obtaining". I forget if you can print from the student version to a plotter? If you can, sweet. All you would have to do is draw the fram, check tolerances and interferences in the 3d model (which is a hell of alot easier with more complicated suspension designs) and then take the file to like kinko's and have them print it out full scale. For the amateur home builder thats more than enough to get started, so long as you dont go CNC part crazy and fabricate stuff that can be fabricated.

LMC · Jul 11, 2008

MobileChernobyl said:
Thats a clever idea, I would suggest Rick's suggestion over the mention of "obtaining". I forget if you can print from the student version to a plotter? If you can, sweet. All you would have to do is draw the fram, check tolerances and interferences in the 3d model (which is a hell of alot easier with more complicated suspension designs) and then take the file to like kinko's and have them print it out full scale. For the amateur home builder thats more than enough to get started, so long as you dont go CNC part crazy and fabricate stuff that can be fabricated.

i agree with all the above..

about the cnc parts its a good idea for amateur builders to watch a 5 axis cnc machine in operation, (theres likely to be videos on youtube) to give u an idea of what can and cant be done.
For example if i have to turn the part over will i be able to relocate it in the clamps in the exact position i need?..

FlyinPolack · Jul 11, 2008

Find a bike that you like & someone with a jig that you can stick that frame into. Take some measurements, cut some pipe, & weld it all together.
Then ride it with glee. Take it from someone who knows:biggrin:

If you want to learn SW that's great, but it's not at all necessary.

CraShRyDer7 · Jul 11, 2008

good luck, i wanna see how this will turn out

demo 9 · Jul 11, 2008

can somebody please help me get solidworks. PM me, i cant find a trail or "obtain" a copy either, i have a good idea i want 2 make

dirtdigger · Jul 11, 2008

EB-Mitchell said:
Hi. I have been working on a DH frame for about 2 and a half years now... It is very difficult to get things right. My suggestion is to download the try out version of cadopia IntelliCAD for 2d and then the trail version of rhino to convert it to 3d. It would also be best to take a short course on cad at your local school or something. Here is my final design (I am in the process of mitering the tubes and machining).

hey looking good, but you may want to raise that main pivot some (like 30-40mm) as you will get lots of chain torque squat and from acceleration forces as well due to central mass rotation of the main frame and rider.

have fun!

buildyourown · Jul 11, 2008

LMC said:
i agree with all the above..

about the cnc parts its a good idea for amateur builders to watch a 5 axis cnc machine in operation, (theres likely to be videos on youtube) to give u an idea of what can and cant be done.
For example if i have to turn the part over will i be able to relocate it in the clamps in the exact position i need?..

Designing parts that have to be done on a multi axis machine is stupid. 3 axis machine time can be had for as low as $75/hr. 5 axis STARTS at about $200.

Design your parts so they can be done in 2 operations. A top and a bottom. Sure, sometimes this isn't possible. Just remember that a 3rd operation, may add 30% to the price.

LMC · Jul 11, 2008

buildyourown said:
Designing parts that have to be done on a multi axis machine is stupid. 3 axis machine time can be had for as low as $75/hr. 5 axis STARTS at about $200.

Design your parts so they can be done in 2 operations. A top and a bottom. Sure, sometimes this isn't possible. Just remember that a 3rd operation, may add 30% to the price.

ive had many parts created on a 5 axis and ive never paid anywhere near $200/hr,

but yes, keep it as simple as possible.

to the OP. this thread is going to be pure speculation until we have a better idea of what is trying to be created, do you have any sketches/more details you can post?

ChrisKring · Jul 11, 2008

dirtdigger said:
hey looking good, but you may want to raise that main pivot some (like 30-40mm) as you will get lots of chain torque squat and from acceleration forces as well due to central mass rotation of the main frame and rider.

have fun!

you are incorrect. The resultant moment about the pivot from the chain pull is less than the driving force from the contact patch of the tire in the opposite dirrection. Draw the free body diagram. I didn't believe DW's statement regarding this until I drew it out.

Low pivot bikes squat under acceleration due to poor low speed compression.

ChrisKring · Jul 11, 2008

blank said:
Well, long story short, i got a job at a metal shop and have the opportunity to actually make a frame of my choice. Problem, i don't know **** about designing let alone don't have enough money to learn the programs i want to use..

So, does anyone have any frame designs that i could use? I would ideally want a high piviot 5'' frame. Steel it is going to be no mater what. 66-67 degree headtube? 22 tt? linear rate?

Not sure really, but if people have designs that could be made, post em up!
Thanks!

so back to the original request, the guy doesn't want to use cad. Why is everyone suggesting that he steal a copy of XYZ program, learn to use it and then maybee build a frame?

dirtdigger · Jul 11, 2008

ChrisKring said:
you are incorrect. The resultant moment about the pivot from the chain pull is less than the driving force from the contact patch of the tire in the opposite dirrection. Draw the free body diagram. I didn't believe DW's statement regarding this until I drew it out.

Low pivot bikes squat under acceleration due to poor low speed compression.

how can i be incorrect when you say low pivot bikes squat?? using low speed compression just fixes the problem.

the force from the rear axle to the point where it is attached on the frame, above or below the CG will determin the squat/ jack you will get from acceleration forces, well thats what i was thinking maybe i'll look at the tire patch thing?

anyway my S.O.M.P (seat of my pants)testing on my high pivot bikes leeds me to this being the case,

buildyourown · Jul 11, 2008

LMC said:
ive had many parts created on a 5 axis and ive never paid anywhere near $200/hr,

Then the parts either weren't done on a 5 axis machine, or the shop was starving for work and giving their time away.
Or the machinist was horribly under paid and needs to wake up and smell the job market.

dirtdigger · Jul 11, 2008

blank said:
indeed thats what it is. I really just don't have time to learn and fully design a frame. Hence, i am asking if anyone has a design i could use...unless someone is willing to spend the time and design one for me...with my input of course.

Its a bike frame, inless it has really messy linkage i really only need angles, piviot location and tube length, from there i can make it how i like.

Also realize, i don't have a frame jig...if i had one i don't think i would need help...

So ideally....
5'' rear, linear rate, high piviot (reason on 5'' is i live in ontario...there isn't much =P)
low stand over
22'' tt? 66-67 degree headtube angle
regular spacing

Single pivot is simplest i think. Less fabrication, in the sense make front triangle, and arm..done!High pivot should ride decent for dh ...

BUT, like i said, if you got a design shoooow mmmme!
(probably repeated alot of ****, but meh...)

you will need a design that will work with your fab skills and the the workshop gear you have at your disposal, have you owned or riden many fullsus bikes? what do you like?
as for the geo numbers thats some thing you'll have to do some research on, take a bike you like and make the changes to the geo to what you want, its all part of the building process.

anyway heres a pic for you

ChrisKring · Jul 11, 2008

dirtdigger said:
how can i be incorrect when you say low pivot bikes squat?? using low speed compression just fixes the problem.

the force from the rear axle to the point where it is attached on the frame, above or below the CG will determin the squat/ jack you will get from acceleration forces, well thats what i was thinking maybe i'll look at the tire patch thing?

anyway my S.O.M.P (seat of my pants)testing on my high pivot bikes leeds me to this being the case,

Bike squat is typically from the rider mass bouncing up and down. AKA, bouncing your whole body up and down while pedaling. Low speed compression damping can help with that.

I'll try to make a diagram later. Basically, the force from the tire contact point is opposite to the chain tension.

allsk8sno · Jul 11, 2008

i disagree, if there is a pivot on the beam, the beam will tend to buckle

dirtdigger · Jul 12, 2008

ChrisKring said:
Bike squat is typically from the rider mass bouncing up and down. AKA, bouncing your whole body up and down while pedaling. Low speed compression damping can help with that.

I'll try to make a diagram later. Basically, the force from the tire contact point is opposite to the chain tension.

yeah some kinda diagram would be cool,

there are 3 things(that i know of) that cause suspension squat/jack and compression, one is the rider mass movement or RMM, i see this as compression not squat and can be controlled by good pedaling technique.

next you have acceleration forces and if your suspension squats from this(low pivot) no amount of good pedaling can stop it.

and then theres chain torque induced squat and or jack and the chain line has an effect on this, when you change the amount of torque on the chain and change the chain line by what gears you use and how much power you put in to the pedal stroke your suspention will jack/squat a certain amount, the major flaw with mtb suspension is the drive chain, the chain line/torque does not go in the direction of the central mass.

dirtdigger · Jul 12, 2008

blank said:
dirtdigger that is exactly what i want to make. High piviot similar to the balfa 2step. If i get the dimensions i can then see what i can fabricate with what i have.

I might just make a hardtail. re-make a 04 torrent with a few tweaks and outta steel..ideally i could make it a 4'' fully or something, not sure...
Any more info on that frame?

yeah thought you'd like it, its not one that i've made tho, but heres a link for ya

http://www.farkin.net/forums/showthread.php?t=114880&highlight=HOME+MADE

ChrisKring · Jul 12, 2008

alright, you guys are correct that the pictured model appears that it may have a very small chain induced squat. However, that is very dependant on the rear cog size, front sprocket size and the exact position of the pivot and bottom bracket. The attached free body diagram shows the forces and resultant moments about the pivot. The design appears to be nearly neutral under pedaling. A 1" shift in the pivot location od a gearing change would change the anaylsis.

If I missed something in the analysis, post up.

LMC · Jul 12, 2008

buildyourown said:
Then the parts either weren't done on a 5 axis machine, or the shop was starving for work and giving their time away.
Or the machinist was horribly under paid and needs to wake up and smell the job market.

neither, he is very well paid. i generally sit with him to make sure hes not slacking for some of the time i pay him for, which is how i know that for most jobs a 5 axis is used. However i do live in the UK so i understand things may be a little different for you.

Blank: if the bike posted by dirtdigger is what you are after then my advice about the linkage software would be all you would need to produce a printout of the geometry required. this can then be tweaked on the paper, then the tubes etc fabricated by hand. Linkage software is easy to use and takes no training.. you can export the file to BMP, JPG format, as well as DXF (autocad format)

Time to make a frame =)

Chimp

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KESSLER PROBLEM. Just cause

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