Cad designed Dualie - Homemade dualie

[Ryder]

Hi i was stuffing around with cad all weekend to get this right, tell us what you think, its a horst link 4 bar link with an altered shock position. Do you reckon it would make a decent dh bike?
Any comments sujjestions are appreciated

Thanks Ryder enjoy.

Every thing is pretty much to scale not exact but pretty good
67 degree head angle with 8" fork shown

[bolzy]

looks like a sweet idea nice work

[Rik]

Hmmm, LTS-esque shock actuation. Dunno about the BB-centric pivot, nor the overly long links... they could cause headaches with construction and rideability.
Pretty unique though, looks like something Nicolai would make.

[DamoH]

What do you use Solidworks for. I am an Industrial Design Student and am just curious.

[Ryder]

Im doing engineering and we use it for our cad subject at uni, its a pretty awesome program easy to use and so powerful.

[S.]

Reckon you could manage to engineer that stem on the right way? :p

Just got a few Q's:
- Why the shock layout you've got there?
- Why the BB-centric pivot?
- Can you list the geometry (wheelbase, chainstay length, bb height) please?

And if you're actually going to build it, I'd recommend a head angle at least 1 degree slacker (2 would be ideal). 67 with an 8" fork is pretty steep.

Looks interesting though.

[Ryder]

Reckon you could manage to engineer that stem on the right way? :p

Just got a few Q's:
- Why the shock layout you've got there?
- Why the BB-centric pivot?
- Can you list the geometry (wheelbase, chainstay length, bb height) please?

And if you're actually going to build it, I'd recommend a head angle at least 1 degree slacker (2 would be ideal). 67 with an 8" fork is pretty steep.

Looks interesting though.


yeah the stem is a bitch i cannot get it to stay where i want it in the assembally of the parts. ill get the geometry and post it, umm i dont know heaps about design of bikes but am constantly learning, i thought bb pivot because it was neat simple and would provide a rigid mounting for the chainstay. Any sujjestions on how i could make it better are grately appreciated.
I would be worried if i were to make it of the flex that would be created in the really long seatstay link.
Also can someone tell me a specialized horst link four bar link is going to be flexier than a stinky setup for example because the stay the wheel is attached to is not attached directly to the mainframe but only by pivots. would this be correct reasoning?

Also if anyone has pictures of anything similar to this design could they post them.
Thanks for the positive comments.

[flyingmonkey*(+.+)*]

looks sweet man, ive played around with a program simmilar to that **good fun**


im not keen on the rear end tho, i think that possibly there may be too much force on the longest part of the rear linkage.

created more so by the force of landing **either rough or off balance**


looks v v good tho, nice work!

[S.]

Try doing a parallel mate between the side face of the stem, and the side face of one of the links or the dropouts or something. Click "aligned" or "anti-aligned" and it should switch it round and face the other way.

BB pivot may be alright, just make sure you've got enough room for some nice wide bearings; use an 83mm BB shell for sure. A cool feature would also be to integrate ISCG or ISCG05 mounts directly into the swingarm (shamelessly stole that idea from Rotec's RL9) for excellent chainguide alignment at all times.

To combat flex, try adding a brace and/or a swing link just in front of the seat tube, and make sure you use decent sized pivot axles and good bearings (needle roller bearings preferably). Also use a wide hub spacing (150mm would be ideal).

As for the flex thing comparing FSR to seatstay linkages, yes and no. For a given standard of build they should be fairly similar, but when push comes to shove, the stiffest way to make a rear end is to use a linkage-driven singlepivot (or singlepivot with swing-link a la Foes) with a short stiff linkage and a nicely triangulated swingarm (think Turner DHR, Ventana El Cuervo, Yeti ASX etc).

Closest thing I've seen to your design would be the Turner Highline. Run a search here, some pics were posted up a few weeks back.

[Byatch]

I"m no engineer, but to me it looks like there might be limited space in the linkage design for the rear shock.
Is this something that you've had a look at yourself?

[Ryder]

I"m no engineer, but to me it looks like there might be limited space in the linkage design for the rear shock.
Is this something that you've had a look at yourself?


yes the link would have to be thought out a little more other wise the shock would hit\rest on the downtube. I think if i was to make it the seatstay link would be made as short as possible to reduce the flex that would be created in it. also it would be braced as much as possible.

[whywalkwhenucanroll]

Looks cool, 10 points for effort mate.

I would shorten off that seatstay a tad to bring the rear shock closer to the seat tube. All that will do is make the stay a bit stiffer and give you a little more room to move. I'd also steepen the angle of the fourth bar (um, linkage plates?) to raise the shock away from the down tube a little. It looks the goods and should make an interesting experiment. Do you have any plans to make it?

[RaID]

well first of all we need more info on all the geo
ie wb, cs length, tt, bb height etc

the mounting of the shock could definately use some work
in the current arrangement you dont have ny room for a springm collar
and other bits and pieces that are on a rear shock,

in your engineering course have you done much on load analysis yet?
youre putting a high bending load on the seat stay by mounting the shock
the way it is, you should try to eliminate that.
Ie try to put all the loads in compression or tension as much as possible


the BB pivot needs to be much bbigger to accomidate bigger bearings

plus you have to take into account the shock rate, wheel path to determine what kind of ride you want

your design is similar (minus the BB pivot) to this bike
Devinci
http://www.devinci.com/image/can_an_2005/ollie_big.jpg

or the Turner Highline on the http://www.turnerbikes.com/ website

analyse these 2 frames froma structural point of view and see why they have designed the way it is?
ie do some backward engineering
look at manufacturers that have used the features you have on your frame
eg BB pivot, horst link with that shock actuation.....
and try to understand why they have done something

you dont have to reinvent the wheel everytime


nice work
what year engineering are you?

[Ryder]

im afraid that im only doing second year at the moment and have only really started load analysis, yet all of this helps, it is very similar to the ollie in many ways and i would be interested to find out the ad/ disadvantage of a bb centric pivot i was under the impression that with zero chain growth you wouldnt couldnt receive any pedal feed back that a specialized horst link would suffer from. also im going to have a look at the geometry of all the downhill bikes that i can find and try and work out the most common geometry.

Also it interesting that there are so many single pivot bikes in the world cup, lots of prople like them because there arent any links that will soak up any pedalling power. yet many claim that thier bikes using link systems are the best pedalling out of the lot.

what pedals better in people opinions single pivots or linkage bikes with the same shock technology.

Also things like the santa cruz vpp bikes are they all they claim to be? or is it all marketing hype. Im really interested to find out what the majority of people prefer to ride dh.

It would be interesting to get a bike on a dyno of sorts and see which system actually provides the wheel the most power. However with the advantation of spv(stable platform systems) people rejected them because they got rid of small bump capability IMO that was manitous biggest mistake ever putting spv on a darado because as far as i know no one bought them simply because they wanted to retain thier sensitirity

[echo]

smart thinking man. looks awsome

[S.]

im afraid that im only doing second year at the moment and have only really started load analysis, yet all of this helps, it is very similar to the ollie in many ways and i would be interested to find out the ad/ disadvantage of a bb centric pivot i was under the impression that with zero chain growth you wouldnt couldnt receive any pedal feed back that a specialized horst link would suffer from. also im going to have a look at the geometry of all the downhill bikes that i can find and try and work out the most common geometry.

Also it interesting that there are so many single pivot bikes in the world cup, lots of prople like them because there arent any links that will soak up any pedalling power. yet many claim that thier bikes using link systems are the best pedalling out of the lot.

what pedals better in people opinions single pivots or linkage bikes with the same shock technology.

Also things like the santa cruz vpp bikes are they all they claim to be? or is it all marketing hype. Im really interested to find out what the majority of people prefer to ride dh.

It would be interesting to get a bike on a dyno of sorts and see which system actually provides the wheel the most power. However with the advantation of spv(stable platform systems) people rejected them because they got rid of small bump capability IMO that was manitous biggest mistake ever putting spv on a darado because as far as i know no one bought them simply because they wanted to retain thier sensitirity

BB centric pivots will only give you zero chaingrowth if the bike is a singlepivot (or a singlepivot with shock linkage). In this case, chain growth will be minimal but it won't be zero. The vast majority of FSR bikes have negligible chain growth anyway.

As for link vs singlepivot bikes, you simply can't get the same tunability with a singlepivot that you can with a linkage bike. That said, the vast majority of the industry doesn't know how to use that extra tunability to its advantage (the only system that I know does is DW-link). If you hear what sounds like a simple explanation of why bikes pedal well, disregard it, it's almost certainly bullshit. Most bike designers still don't understand that chain tension force isn't everything (I could go on a long long rant here but I won't). As for "what pedals better, linkage bikes or singlepivot", that question is far to sweeping to answer. Some singlepivot bikes pedal well, some don't, some linkage bikes pedal well, some don't. Ultimately I believe you *can* make linkage bikes pedal slightly more efficiently than a singlepivot, but as far as DH bikes go I'm quite convinced that you can get satisfactory pedalling performance out of certain singlepivot configurations (none of which *exactly* exist, as far as I know).

VPP doesn't really offer any advantages over other systems. People seem to think it's the holy grail of pedaling efficiency (which I can assure you, it's not, in its current configurations at least), neglecting the fact that VPP conveniently reappeared on the market at exactly the same time as SPV/platform shocks. The whole VPP idea (as shown in the patent) neglects some critical components of the forces involved in pedalling. Not to say it performs badly, but it certainly isn't the be-all end-all of suspension. Again, the only suspension setup I am yet to be able to poke holes in is DW-link. Not to say I think it's perfect, but it is based on a proper understanding and full application of physics, not the half-arsed stuff you see in the majority of the bike world.

Putting bikes on a dyno won't give you an accurate readout of how it reacts under power, because the rider/bike mass isn't being accelerated and thus the bike will not behave in the same way as if you were actually riding it. The only way I know of (other than using kinematics) to actually measure the efficiency would be to instrument the bikes themselves with suspension displacement gauges and graph the position with regards to time and pedal strokes. This would give you an accurate idea of how each bike reacts, but then you'd have to make sure all shock rate setups, etc etc were kept as similar as possible.

[whywalkwhenucanroll]

Oh memories... S. what do you do for a living?

An interesting read is that document on path analysis, its floating around somewhere on cyberspace, There was a forum here ages ago about a 222 vs an M1 (something like that) back before some of us new better, it'd be an interesting read though you will wanna check where people come up with their ideas from. Much of what people said was bullshit (myself included). The idea of hooking up a bunch of instruments to a bike and rider was done by Devinci when they were developing their Ollie etc. Check their site it might have some info about it still there.

That said, I agree with S. that many manufacturers seem to put in a half arsed effort to their designs and that VPP could be a lot better then it currently is. Also having read a fair bit of that path analysis thing I think it would be safe to say that having a BB concentric main pivot does little towards actual pedal efficiency. The P.A. document gives a good explanation of how this works if you get a hold of it. There is however other benefits of having a BB concentric main pivot however the horst link in your design will spoil some of these (but not others). It is a good idea remember that path analysis is only one of many tools at a designers disposal for analysing suspension behaviour.

To answer your single pivot vs linkage question as best I can in a short time: It depends on a lot of factors. There is no straight answer to this but you can compare different designs and get an idea of the effects of particular design elements. For example an Orange 222 uses a main pivot located above the working chain line to create "pedal efficiency". It can be shown by path analysis that all this does is use the force of pedalling along the line of the chain to counter the downward force of the rider pushing on the pedal. This is in its extreme a form of lockout and on its own will reduce the "activeness" of the suspension while riding. This is what VPP is said to solve, by using an 's' shaped wheel path they can minimise "peddle bob" and keep the suspension active. Anyway I'm gonna pull myself up there before I fill the entire forum and let you read about it yourself. GoodLuck.

[nicklouse]

will have a look at that in linkage later.

i have some concerns.

bb will have to be a 100mm one really.

some pics of another bb pivoted 4 bar.

http://img216.imageshack.us/img216/4748/im0004405bu.th.jpg (http://img216.imageshack.us/my.php?image=im0004405bu.jpg)
sorry the sun was low!
http://img299.imageshack.us/img299/8297/im0004314yp.th.jpg (http://img299.imageshack.us/my.php?image=im0004314yp.jpg)
http://img276.imageshack.us/img276/8805/im0004337gh.th.jpg (http://img276.imageshack.us/my.php?image=im0004337gh.jpg)
http://img299.imageshack.us/img299/5545/im0004329kd.th.jpg (http://img299.imageshack.us/my.php?image=im0004329kd.jpg)

[RaID]

will have a look at that in linkage later.

i have some concerns.

bb will have to be a 100mm one really.

some pics of another bb pivoted 4 bar.

http://img216.imageshack.us/img216/4748/im0004405bu.th.jpg (http://img216.imageshack.us/my.php?image=im0004405bu.jpg)
sorry the sun was low!
http://img299.imageshack.us/img299/8297/im0004314yp.th.jpg (http://img299.imageshack.us/my.php?image=im0004314yp.jpg)
http://img276.imageshack.us/img276/8805/im0004337gh.th.jpg (http://img276.imageshack.us/my.php?image=im0004337gh.jpg)
http://img299.imageshack.us/img299/5545/im0004329kd.th.jpg (http://img299.imageshack.us/my.php?image=im0004329kd.jpg)


the new rotec DH bike has a simillar design ie BB pivot and lawlink linkage


how does the bike you posted ride nicklouse?

[Ryder]

will have a look at that in linkage later.

i have some concerns.

bb will have to be a 100mm one really.

some pics of another bb pivoted 4 bar.

http://img216.imageshack.us/img216/4748/im0004405bu.th.jpg (http://img216.imageshack.us/my.php?image=im0004405bu.jpg)
sorry the sun was low!
http://img299.imageshack.us/img299/8297/im0004314yp.th.jpg (http://img299.imageshack.us/my.php?image=im0004314yp.jpg)
http://img276.imageshack.us/img276/8805/im0004337gh.th.jpg (http://img276.imageshack.us/my.php?image=im0004337gh.jpg)
http://img299.imageshack.us/img299/5545/im0004329kd.th.jpg (http://img299.imageshack.us/my.php?image=im0004329kd.jpg)


Thats an awesom bike, you wouldnt want to run a shimano deraliur on it though.
Looks a fair bit like a Proflie dh bike but the shock is activated differently.
That would be a lot of fun to ride.
Whats the rear travel on that frame anyway and how much does it weight if you dont mind.
Edit : it is also a lot like a Yeti DH9 asides from the pivot
thanks for posting that man and have fun riding it

[nicklouse]

23,5 kg!

tis fun and fast swallow bumps like no tomorrow back end stiffens under braking. and about 240mm of travel and i can not get it to work in linkage!!!

[nicklouse]

that design of yours is very similar to some of the turners!