[Pslide]

Right, I've been thinking about this bike for years. I've been modelling it for months. I've been refining it for...ever. It still needs some tweaks, but I'm almost ready to go to metal.

Here are the details:
Aggressive trail bike. 6-7" travel via Fox DHX Air. 853 or similar front triangle and rear swingarm, with flexible chainstays (ala Yeti 575). Aluminum CNC'd rocker link and BB braces. High pivot design (for backward arcing rear travel - ultimate in bump absorbtion) and ADJUSTABLE chain idler pulley. Yeah, this is the first adjustable one I'm aware of - you can set it low to sprint well, or high to minimize pedal feedback. Low CG. Longish enclosed seat tube. All pivots use thru-axles for maximum stiffness in the rear end.

I won't go into geometry, as it's set up for my 6'4" frame, but consider it very similar to a Specialized Enduro - longish TT, short rear end, 67.5 HA.

Construction will hopefully happen by a very high quality builder over here in England. I had FTW look at it a while back, he'd do it (in a previous Aluminum version) for a pretty penny. I thought I'd better post my design now because I heard he's coming out with a new design - just in case it's something similar!!!

Regardless, the steel bike will use the sexiest of all joining methods...fillet brazing. Steel was used for it's compliance and fatigue resistance - steel is still real.

What does everyone think?

 

[manhattanprjkt83]

cool.

 

[sneakysnake]

Thats pretty awesome.

 

[Honus]

Cool design. Gotta love a fillet brazed bike! I'd be a bit concerned about the lower stays and the flex joint. Speaking from experience in brazing frames, it looks like it would break right at the dropout at the lower stay joint. How long is the flexible section and how thick is it? Why not TIG the flexible section directly to the dropout and properly reinforce it and then braze the other end of the flexible section to the lower stays?

 

[wil_e123]

do you have a cinematic diagram to show how the rear triangle will take the suspension through it's travel (in other words the path that the suspension will take)? i'd just like to see what it's like to get an idea of how it will work, i'm not saying it won't since you seem to have put a lot of reasearch into the design stage, it's just that i'm a bit confused...

good idea to use steel, it's more original and, as you said, has a better fatigue resistance.

cheers, and best of luck with the production stages!

 

[Pslide]

Honus: Yeah, the flexing part of the stays is one thing that needs tweeked! I was going to put a plate gusset between the seatstay and chainstay to reinforce that area and keep it from flexing at the drop out. I probably wouldn't have to TIG it that way. And I'm planning to use high carbon steel for the flexible part. The chainstay itself will be quite thin steel tubing, which will have some natural flex anyway. The amount of vertical deflection that stay will go through is about 20 mm at the free end...I thought that was too much without including a flexible piece in there.

Thanks for your input! It's definitely a critical area of the design...

 

[Pslide]

do you have a cinematic diagram to show how the rear triangle will take the suspension through it's travelQUOTE]

Sorry Wil, I can move it in my program but I don't know how to make an animation. But you can visualize it quite easily - the center of the radius is at the big main pivot above the shock. So, take the point of your compass and stick it on the pivot, and draw an arc through the rear axle. It's quite rearward and becomes more vertical as it progresses...

Glad you like it!

-Aaron

 

[firevsh2o]

Looks like a GT (RTS or so) of old.

 

[Bicyclist]

Hrm, a fillet brazed FR/AM bike...

 

[Pslide]

Hrm, a fillet brazed FR/AM bike...

Hey, have you ever heard of a fillet brazed bike failing? Under any circumstance? If so, I'd like to know about it! Fillet brazing is rare not because it's weak, but because it's time comsuming and requires high precision. ($$$)

And Fire, you're right about the RTS relation! Except the idler pulley will negate the pedal feed back issue, and new shock technology will enhance the effectiveness. It's also not far off a new Trek Session 10, a PDC Solaris, or the Balfa BB7.

-Aaron

 

[Pslide]

And when I looked at that new Lahar, I almost blew a valve...the suspension design is almost identical. It's not exactly revolutionary (nothing much is anymore), but it hits all the right buttons in my book...

 

[xy9ine]

And when I looked at that new Lahar, I almost blew a valve...the suspension design is almost identical. It's not exactly revolutionary (nothing much is anymore), but it hits all the right buttons in my book...

the pdc solaris uses a similar system as well. don't think there's idler pulley adjustability, though.

i love the idea of fillet brazing, though. i still lust after vintage brazed rocky's, brodies, & toads. hairy gary is still building brazed dh / fr bikes i believe.

 

[S.K.C.]

Nice CAD work Pslide - looks as though you've done your homework.

Very cool looking indeed.

 

[Biscuit]

That is bad-ass. I dig the concept. I like the adjustable ideler too.


Looks like it will be heavy though.

 

[DVNT]

Sorry Wil, I can move it in my program but I don't know how to make an animation. But you can visualize it quite easily - the center of the radius is at the big main pivot above the shock.

Try this, it comes in handy especially when e-mailing designs to freelance clients.

eDrawings offers unique capabilities like point-and-click animations that make it easy for anyone with a PC to interpret and understand 2D and 3D design data.

for solidworks

 

[Superdeft]

is that solidworks or solidedge?

 

[Bearmntpicnic]

that is really cool steel is where its at although it will most likley weigh a ton like those brooklyn bikes 63 ponds or something. It looks really good.

 

[Ascentrek]

I commend your effort! You need to model the pivot design a bit. you should look into "linkage" a bit.

Do you have an engineering degree? You've put quite a bit of effort into this, but I think a few things could be improved.

A few things to consider....

The rear pivot is extremely high. This will cause the axle path to extend the chain line... a lot. If you don't like the 'buck' that elevated chain lines produce, you may not like it exagerrated. High pivot points also tend to 'catch' on obstacles vs. suspend. This design looks as if it might compress due to catching an obstacle.

If that is your main pivot, you'll need to beef up your swing-arm. I like the idea of using 'tension' to reduce the chain-tube, but it will only add to the flex. This will in turn put adverse forces on the bearings.

The Main Pivot seems wide (It is hard to tell), be consious about where that may hit your leg.

These are only suggestions. I still like what you've done considering it seems harder and harder to create a unique suspension design.

 

[Superdeft]

I have a question: when determining head tube position using fork wheel size, fork rake, fork and headset height, what wheel size did you use.

In short: how large did you assume your rim + inflated tire diameter would be?

 

[amateur]

It's SolidWorks.

Subterranean fillet brazed his/their bikes. Strong, but too time consuming for most production bikes.

Looks pretty solid, but I agree with the high pivot comment.

 

[OGDMFG]

Hey pslide you might want to also beef up the area around the pulley wheel all the torque might twist that into a pretzel, looks good

 

[SuspectDevice]

Looks damn fun. I agree that the main swingarm needs to get triangulated. If you go to more pin-tube style construction you should be able to up the stiffness in the back end. I'd double some .5"x.035 tubing with a piece of .75"x .035 tubing stuck across as a tie-member. You could do something similar with the stays. Pin-tube construction is so fun, it's more like constructing a building than a bike.


Also, contact Stendec about getting a Cane Creek double barrel for that bike. The super huge tuning range will be ideal to iron out any quirks you may find...

Looks rad!

 

[banj]

Hey Pslide. How high is you pivot above the bb and what's your bb height?

 

[SteezyWeezy]

nice job

 

[OGRipper]

The rear pivot is extremely high. This will cause the axle path to extend the chain line... a lot. If you don't like the 'buck' that elevated chain lines produce, you may not like it exagerrated. High pivot points also tend to 'catch' on obstacles vs. suspend. This design looks as if it might compress due to catching an obstacle.

The the idler pulley will reduce the chain growth, and he says the path is "quite rearward," so I think he is aware of these issues and has tried to balance them with other factors. Pretty cool. I like the idea of a fillet brazed steel frame like this but not sure it's optimal for performance - weight, stiffness, etc.

 

[LaharDesign]

Ascentrek: I commend your effort! You need to model the pivot design a bit. you should look into "linkage" a bit.
The primary use of linkages by the industry is to keep the market confused. Good wheelpath and independance of drive and braking are objectives that can be achieved with any susp conf. Pslides design will produce better stiffness than a girder or any single pivot execution of this design because the triangulation distributes load thru 2 widely seperated points on the frame.

The rear pivot is extremely high. This will cause the axle path to extend the chain line... a lot. If you don't like the 'buck' that elevated chain lines produce, you may not like it exagerrated. High pivot points also tend to 'catch' on obstacles vs. suspend. This design looks as if it might compress due to catching an obstacle.

Chainline: wrong, the idler fixes this.
Buck: this is a function of low pivots not high. If you hit a big bump with a low pivot it cannot respond fast enough as the neccesary suspension acceleration to get the wheel clearing the bump tends towards infinite.
High pivots do not catch on obstacles, the suspension deals with them. Low pivots convert most of the energy from any bump over 4 inch into a yank along the chainstay, subtracting from forward motion in a way that pitches the mainframe forwards violently.
High pivots like Pslides use all the bumpforce to actuate the susp, have considerably less peak wheel accel and velocity as they deal with the bump and never buck.

If that is your main pivot, you'll need to beef up your swing-arm. I like the idea of using 'tension' to reduce the chain-tube, but it will only add to the flex. This will in turn put adverse forces on the bearings.

Pslide your design as drawn will be a market leader in lateral stiffness. Eliminating the pivots at the rear dropout will assist with stiffness. I'd like to see a steel leaf silver soldered in at the flex point but your 20mm movement at rocker end is 1/4 of what I'm engineering for in my 9th installment of this layout since 1997.

The Main Pivot seems wide (It is hard to tell), be consious about where that may hit your leg.

Doubt it. its inside your crankarm.

Well done Pslide. My only concern is that the adjustable idler has to handle up to 700lb of chainforce. I'm sure once you know where you want it you'll braze it to the frame or swingarm anyway.

 

[LaharDesign]

Looks damn fun. I agree that the main swingarm needs to get triangulated. If you go to more pin-tube style construction you should be able to up the stiffness in the back end. I'd double some .5"x.035 tubing with a piece of .75"x .035 tubing stuck across as a tie-member. You could do something similar with the stays. Pin-tube construction is so fun, it's more like constructing a building than a bike.


Also, contact Stendec about getting a Cane Creek double barrel for that bike. The super huge tuning range will be ideal to iron out any quirks you may find...

Looks rad!

triangulated girders are great for static loads but have poor energy absorbsion. This layout will eliminate all the horrible "quirks" of conventional bikes and you may get the best results from an old pre-"platform" shock. (actually this is a silly statement, Platform shocks were invented in the late 1800's to try and bandage the same drive and braking probs that conv drivetrain bikes have today. They were junked within a few years with all the scientific-papers published on designing susp properly.- as Pslide is doing)

 

[ragin-sagin]

Oh whatever Lahar dude...its not like you have spent years designing and and refining high pivots. Jeesh.

On a side note: Pslide, listen up, Lahard dude has spent years designing and refining high pivots. Maybe you should chuck that pulley in favor of an internally geared hub...

 

[bikenweed]

Great design! I'm willing it bet it ends up being very light. Steel is an excellent material for a DH frame. Aluminum has to be so oversized and reinforced to take DH abuse that it often ends up so over built it weighs more than a simple steel alternative.


If ya can, spec it with an 8.75" eye to eye shock. It's pretty easy to find 8.5" and 9.0" i2i sizes, and this will allow you to tweak the geometry a bit without any massive frame changes.

Looks great, and plz let me ride the first prototype!

 

[mandown]

The rear pivot is extremely high. This will cause the axle path to extend the chain line... a lot. If you don't like the 'buck' that elevated chain lines produce, you may not like it exagerrated. High pivot points also tend to 'catch' on obstacles vs. suspend. This design looks as if it might compress due to catching an obstacle.

Chainline: wrong, the idler fixes this.
Buck: this is a function of low pivots not high. If you hit a big bump with a low pivot it cannot respond fast enough as the neccesary suspension acceleration to get the wheel clearing the bump tends towards infinite.
High pivots do not catch on obstacles, the suspension deals with them. Low pivots convert most of the energy from any bump over 4 inch into a yank along the chainstay, subtracting from forward motion in a way that pitches the mainframe forwards violently.
High pivots like Pslides use all the bumpforce to actuate the susp, have considerably less peak wheel accel and velocity as they deal with the bump and never buck.

thanks for that. i was pretty certain his argument was off, but i didn't want to put my foot in my mouth and taste my shoe. i figured i would wait until someone who knows this stuff made the statement.

 

[thaflyinfatman]

triangulated girders are great for static loads but have poor energy absorbsion. This layout will eliminate all the horrible "quirks" of conventional bikes and you may get the best results from an old pre-"platform" shock. (actually this is a silly statement, Platform shocks were invented in the late 1800's to try and bandage the same drive and braking probs that conv drivetrain bikes have today. They were junked within a few years with all the scientific-papers published on designing susp properly.- as Pslide is doing)

Just FYI, the Double Barrel is not a platform shock.

 

[CKxx]

Ascentrek: I commend your effort! You need to model the pivot design a bit. you should look into "linkage" a bit.
The primary use of linkages by the industry is to keep the market confused. Good wheelpath and independance of drive and braking are objectives that can be achieved with any susp conf. Pslides design will produce better stiffness than a girder or any single pivot execution of this design because the triangulation distributes load thru 2 widely seperated points on the frame.

I think he may have meant the program "Linkage." I'm not sure though.

http://www.bikechecker.com/

 

[LaharDesign]

I think he may have meant the program "Linkage." I'm not sure though.

http://www.bikechecker.com/

I didn't, he might have.

 

[buildyourown]

Nice modeling work. It took me forever to figure out how to model tubes in SW as an assembly.

A piece of 17-4 PH stainless silver brazed into the stays would make for a good CS pivot. It should be very durable, and if one ever cracked, it would be easy to repair vs something tig welded.

I would be leary of specing 853. With tube junctions in the middle of tubes, you will want something with a heavier wall in that area. This limits your tube choices.

 

[thaflyinfatman]

Nice modeling work. It took me forever to figure out how to model tubes in SW as an assembly.

How do you do it? I haven't worked it out either (other than the slow and tedious ways doing it all as a single part, which sucks).

 

[Pslide]

Wow, you leave work for the night and the thread explodes! Really appreciate everyone's comments, and will do my best to respond...although some have already responded better than I could!

Concerning frame weight: This does concern me! Because I know I can spec 853 and think it will be light (not necessarily any heavier than Aluminum), but when it all comes together, especially with bearings and hardware, I'm worried... Lightweight is a design goal.

Buildyourown, thanks for the tip on 853...perhaps I will use straight gauge on the downtube...or something with a bit more wall thickness (drat...more weight!). And I'll have to check out 17-4 PH for the flex joint. Well he**, sounds like I should be talking to you about building the whole thing!

xy9ine and amatuer, thanks for your hints on builders. I'm not sure my current guy is going to have the time, so I may be on the prowl soon...

Superdeft, yes, it is Solidworks. I've found it very simple to use, and I'll try to respond to that tube modeling question later. As for Fork dimenions, I modelled it after a Marzocchi AM1. I'm a Marzocchi fan...I've been riding Z1s for donkeys years! The dims can be found on their tech section of the website. I did model Axle to Crown and Rake into the main sketch that drives all the geometry.

DVNT, thanks for the link...if I get some time I'll have to make an animation for you guys.

Ascentrek, thanks for your comments. I think LaharDesign pretty much took care of them, and I agree with him. I am a mechanical engineer and I've been studying mountain bike suspension for as long as I've been mountain biking (10 years). I think my design (which is virtually identical to the Lahar, and therefore only loosely "my" design) represents the best thinking, and we're seeing more and more high pivots creep into production. It's mostly the small guys now, but Trek is playing with them and soon I think more big companies will. Credit to Lahar and Balfa...I think they've been doing it the longest!

LaharDesign, you've been gracious! You could have easily walked all over my design as a knock off of the Lahar. You could probably tell that I didn't even know about Lahar when I was thinking all of this up. I do think the Lahar is probably the most sophisticated, forward thinking bike on the planet. As for suspension design, great minds think alike. And I'm not naive enough to think I'm the first to think of something. The question will be how long will it take for other designers to follow suit?

Raginsagin, my first designs were using internal hubs similar to the Lahar! I looked at the Shimano Nexus, SRAM internal hubs, and of course the Rohloff. I decided the technology isn't worth the weight. I could accept the weight on a downhill design, but my design is supposed to be all mountain, and weight is a serious concern. I do believe the future is internal hubs, and that Shimano probably has a skunkworks working on great things. The time will come...

Banj, BB is 13.75" high (with 6.5" rear travel). The pivot is another 185 mm higher than that. So it's slightly higher than a BB7, which is...7 inches (thus BB7).

Bikenweed, you come to me and you can ride it! I want as many people to ride it as possible, because I want to know just how well it works. Looks like I'll be lucky to finish it this year though...it's hard building your own bike! Got to have patience...

-Aaron

 

[thaflyinfatman]

Got a question for you (if you've already answered it, sorry, I missed it!) - are you planning to run a front derailleur, and if so, how? That's the biggest drawback I see to a high pivot trailbike, personally. I'd be interested to see how you'd get around that (if you choose to).

 

[Vrock]

FD Compatibility is very important because it's an AM bike, but I think it's possible. Thylacine Cycles have a similar design but without the shock linkage: High Pivot, Idler pulley and a ¿E-Type? FD rotated to the front.

Pslide, the only thing that I'ld change it's the standover, It'd look better with more slooping and a reinforcement near the seat tube.

 

[Pslide]

Vrock, thanks for the comments. I might drop that top tube, or put a bend in it.

Well done on the FD issue - I completely forgot to mention it! What I've done is integrate it into the idler pulley. The idler pulley runs on a bearing mounted onto a fairly large hollow shaft. It will be run in a slightly larger tube, with ball bearings slotted in the shaft. Both ends will be sealed with o-rings and the whole assembly will be pumped full of grease. I haven't worked out the actuation leverage ratios yet, but essentially the idler pulley will slide back and fourth and shift between TWO gears...a 24T and 36T probably.

Why someone hasn't done this before is beyond me...but I suppose each solution would be bike specific... I think you will see integrated chain guide/front deraillers out soon...

Someone else mentioned the main pivot width. It is wide, but doesn't interfer. I taped two WD-40 caps to my current bike at the correct width and my ankle only touched it once...

And Suspect Device...thanks for your comments as well. I don't have any idea what pin tube construction is! Except that some rims are pinned and welded? If you can give me any graphics, I wouldn't mind learning about it! As for the CC Double Barrell...drool. Add a Ti spring and double drool. Still, I think the future is Air...

-Aaron

 

[Pslide]

Wow, never seen that Thylacine before. What kind of name is that anyway? Pretty cool bike. Aesthetically not the best, but pretty innovative. I wonder if it drops a lot of chains? It's kinda similar to the BB7 really, but I think the BB7 is executed a bit better, with lower CG. Still, any single swingarm bike has to carry the full load of the rider and input shock forces through the swingarm, meaning it has to be built stonger/heavier. It's not the most efficient way to design a bicycle from a force management point of view. Force management...geez, who let out the enginerd!

-Aaron