# RAM Bikes URT Chassis and Quadrilateral Fork



## andrepsz (Jan 28, 2013)

WTF?!?!?!

Anyone knows were to find an animation of this thing working?

This is completely out of the box! very good brainstorming on this!


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## Jayem (Jul 16, 2005)

Two front discs and just one 6" rear...lol...


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## highrevkev (Oct 31, 2005)

How the fork works....

__
http://instagr.am/p/1qSNEAvtun/


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## andrepsz (Jan 28, 2013)

highrevkev said:


> How the fork works....
> 
> __
> http://instagr.am/p/1qSNEAvtun/


It looks like a very long travel on this fork! I'd love to see a vid of the back as well!

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## Deerhill (Dec 21, 2009)

Seat tube is so not sexy :nono:


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## NWS (Jun 30, 2010)

Rear triangle? What rear triangle?

Way outside the box. I like that. But I wonder how it rides.


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## Mudguard (Apr 14, 2009)

NWS said:


> R
> But I wonder how it rides.


Like a hardtail when standing? Love the fork though. I always wanted one of the early Whyte bikes.


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## andrepsz (Jan 28, 2013)

it's a pure downhill bike!


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## andrepsz (Jan 28, 2013)

Did you noticed the rear caliper brake underneath?! It's like...'I am going to make a bike different'....everywhere! 

Also looks like this bike has a self balancing technology.


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## Desidus (Jun 27, 2013)

Back looks sick.. Front looks to be a waste of extra material and too complicated. Overall I love the Mad Max look of this bike though.


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## Deerhill (Dec 21, 2009)

andrepsz said:


> it's a pure downhill bike!
> 
> Sent from my iPhone using Tapatalk


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## andrepsz (Jan 28, 2013)

Deerhill said:


> andrepsz said:
> 
> 
> > it's a pure downhill bike!
> ...


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## NWS (Jun 30, 2010)

The more I look at that frame, the more I'm impressed by how they've managed to package the whole thing in such a compact space along the line from the rear axle to the headset. That was really creative.

And if I understand this thing correctly, it has taken the "virtual pivot point" idea to the next logical step - there's a ton of empty space around the pivot point.  (Which is at the top of the chainring, if I'm not mistaken?)

Bummer about the seat tube though. It's so bent, there's almost no adjustability left.


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## andrepsz (Jan 28, 2013)

I still can't picture how that rear swing works....


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## Procter (Feb 3, 2012)

That thing looks dangerous. The stresses on those small rear pivots, with all the leverage from the long swingarm, seems incredibly high. Secondly it's a URT, the crank is not suspended. Which as we know rides like crap, especially on a DH bike where you never sit. The 4 bar linkage on the fork looks similarly fragile. 

That thing is a piece of art, not engineering.


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## andrepsz (Jan 28, 2013)

Procter said:


> That thing looks dangerous. The stresses on those small rear pivots, with all the leverage from the long swingarm, seems incredibly high. Secondly it's a URT, the crank is not suspended. Which as we know rides like crap, especially on a DH bike where you never sit. The 4 bar linkage on the fork looks similarly fragile.
> 
> That thing is a piece of art, not engineering.


I'm sure they did stress tests?!

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## Procter (Feb 3, 2012)

^ you got a lot of faith.

I'm sure they did. I mean, they wouldn't publish pictures of it if they didn't. Who does that. 

Most bikes have a rather heavy main pivot, which takes the majority of the lateral stresses. On my firebird and my flatline it's a m8, and that's with chainstays that are 16-17 inches. The urt chainstay here look at least 22-24 inches, which, due to simple leverage, would impart 40% more force, given the same riding conditions. That would be m10 territory, and that looks like maybe an m6 in the pic. Not to mention the stresses on the top tube. . .


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## NWS (Jun 30, 2010)

The thing that made the old URT bikes suck is the fact that the pivot points were in bad places, not the fact that the BB was attached to the chainstay. But people with no understanding of physics made up some bad theories and repeated them so much that it's practically taken as gospel now.

The bike industry has done a "good" job of convincing people that the nature of the linkage is what matters, that there are now tons of people out there who have no idea that axle path even matters. (Most of them are on pinkbike, but not all.)

You know what else has the BB attached to the chainstay? Specialized P-Slope. OMG it must ride like a hardtail and it only works because those slopestyle guys are always sitting down!!!11!1!!


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## NWS (Jun 30, 2010)

Also, the guy behind Ram Bikes is 6'6", weighs 280, and his been building his own bikes for years using variations on this design. I'm willing to assume that he's figured out how to make the pivots strong enough.


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## fishwrinkle (Jul 11, 2012)

andrepsz said:


> Did you noticed the rear caliper brake underneath?!


yeah it looks vulnerable.


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## andrepsz (Jan 28, 2013)

fishwrinkle said:


> yeah it looks vulnerable.


I agree...questionable

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## Pau11y (Oct 15, 2004)

Is it me or does that thing look like the rear wheel will tuck under the saddle when the shock compresses?


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## Mudguard (Apr 14, 2009)

NWS said:


> You know what else has the BB attached to the chainstay? Specialized P-Slope. OMG it must ride like a hardtail and it only works because those slopestyle guys are always sitting down!!!11!1!!


Erm, the P Slope pivots around its bottom bracket. So it's a simple single pivot. Not URT. The suspension works if you're sitting or standing. And you wont feel the impacts through your feet like URT. 
It's pretty easy to replicate how a URT rides. Just stand on your chainstays instead of your pedals.


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## NWS (Jun 30, 2010)

URT is an acronym. The letters stand for Unified Rear Triangle. That refers to bikes that have a single rigid piece to which the bottom bracket, rear axle, and chainstays are attached. Those are typically part of a triangle with portions that look like seatstays and a seat tube - but those parts don't actually connect to the seat.

Here is an older example, with a very high very forward pivot:

TeamCow / The BikeGuide: Schwinn pt. 3

Here is a newer example, with a pivot that is concentric with the bottom bracket:

Specialized Bicycle Components

Notice that in both cases, the rear triangle (chainstays, seatstays, BB, rear axle, etc) is a unified hunk of metal.

Both URT.

Totally different ride, because totally different pivot placement.


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## NWS (Jun 30, 2010)

Also, if you actually stand on your chainstays, you'll be putting your feet in the middle of the stays, which means you'll have half as much leverage on the rear suspension when you load the bike. So the suspension will compress only half as much. So it will feel half as soft / twice as stiff. Which sucks, but it sucks because the geometry sucks, not because there's anything inherently wrong with URT.

Correlation is not causation. 

Companies tried to sell tablet computers running Windows back in 2003-2004, and they sucked. Lots of people assumed that table computers were just a terrible idea, doomed to suck. But look at iPads today. There's nothing inherently suck about URTs or tablets, they just need to be built by companies that know how to make customers happy.

Y'all are still in the "OMG, they tried that years ago, it sucked" frame of mind. URTs sucked a decade ago because companies were putting the pivots in the worst possible places. They stopped sucking (see the p-slope) when companies started putting the pivots in reasonable places.


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## Mudguard (Apr 14, 2009)

NWS said:


> URT is an acronym. The letters stand for Unified Rear Triangle. That refers to bikes that have a single rigid piece to which the bottom bracket, rear axle, and chainstays are attached. Those are typically part of a triangle with portions that look like seatstays and a seat tube - but those parts don't actually connect to the seat.
> Notice that in both cases, the rear triangle (chainstays, seatstays, BB, rear axle, etc) is a unified hunk of metal.
> 
> Both URT.
> ...


I'm confused, how is the Specialized URT? The BB is independent of the rear axle. A concentric pivot around the BB is isolating the rear wheel from the pedals ultimately. It's not part of the Unified Rear Triangle?


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## NWS (Jun 30, 2010)

The BB is part of the rear triangle. It is rigidly attached to the rear axle. How is that NOT a unified rear triangle?

You seem to be having a hard time separating the concepts of rear triangle and pivot location.


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## Boulder Pilot (Jan 23, 2004)

NWS, the P-Slope is not an URT. You seem to be having a hard time separating the concepts of rear triangle and pivot location.


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## sandwich (Sep 24, 2005)

NWS said:


> The thing that made the old URT bikes suck is the fact that the pivot points were in bad places, not the fact that the BB was attached to the chainstay. But people with no understanding of physics made up some bad theories and repeated them so much that it's practically taken as gospel now.
> 
> The bike industry has done a "good" job of convincing people that the nature of the linkage is what matters, that there are now tons of people out there who have no idea that axle path even matters. (Most of them are on pinkbike, but not all.)
> 
> You know what else has the BB attached to the chainstay? Specialized P-Slope. OMG it must ride like a hardtail and it only works because those slopestyle guys are always sitting down!!!11!1!!


oh god.

the thing that made old URTs suck was that URTs suck. Stinkbugging under braking, stiffening while standing (which is when you want your suspension to actually work), bobbing under pedaling...URTs were a solution to a problem just like saying the earth is the center of the universe was also a solution...there's a better answer now.

Axle path is or can be important, but other factors are much moreso. Anti-squat and braking behavior are two of them. Geometry is probably even more than that. And leverage rate is essential when paired with a suspension design. Axle path certainly has an effect, but I would argue that most bikes have similar axle paths to one another, and the effect on chainstay length can affect the handling of the bike and upset any benefit to the higher pivot.

As for the P.slope, it's not a URT (unified rear _triangle_) but I could see the argument for saying it is one. It also sucks to pedal, because the BB is on the pivot.


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## NWS (Jun 30, 2010)

sandwich said:


> the thing that made old URTs suck was that URTs suck.


Not a big fan of root cause analysis, eh?


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## rep_1969 (Mar 25, 2004)

Wow, riding that thing would be like riding a slinky down some stairs. Scary.


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## shupack (Nov 28, 2012)

andrepsz said:


> I still can't picture how that rear swing works....
> 
> Sent from my iPhone using Tapatalk


the VPP is about 4" above and 4" behind the bottom bracket, so as the wheel moves up, the bottom pivots move forward/down, swinging the links forward. Visualize the shock compressing, and work backwards from there..... I think.


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## NWS (Jun 30, 2010)

You can approximate the effective pivot point by drawing lines through the physical pivot points and seeing where they intersect.









So yeah, above and behind the BB, like shupac said. As the suspension compresses, the effective pivot point moves down and forward, due to the way the links move. That motion is harder to visualize.

The guy who designed the bike said the effective pivot was near the BB, so maybe it ends up when the rider is on the bike? It moves in that direction, but I kinda doubt it moves quite that far... but I can only guess.


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## Lelandjt (Feb 22, 2008)

URTs are URTs and concentric single pivots are concentric single pivots. They are not the same thing. The defining characteristic of a URT is the BB is part of the swingarm. On a Concentric bike the BB is part of the main frame. URTs ride like sh!t not because of their pivot placement (lots of different pivot placements were used from the top tube to just in front of the BB) but for 3 other reasons:
1. They have no anti-squat to counteract the bobbing of your weight as you pedal and the rearward weight shift of acceleration.
2. They stiffen when you stand. Standing and coasting is when you want the suspension plushest.
3. The pedals move in relation to the seat and handlebar.

They closest thing to a URT still in existance is GT's design which changes the amount and direction the BB moves to minimize the negatives while still minimizing chain growth on a high pivot design.

P.S. No anti-squat is what also makes concentric single pivots no good except for park bikes.


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## NWS (Jun 30, 2010)

With concentric single pivots the BB is also part of the swingarm. It's funny that you simultaneously think that this is the only thing that makes URT suck, and yet.. pivot placement doesn't matter.

Given the pivot placement on the RAM bike in the first post of this thread, I'd wager a buck that it's actually softer when you stand on the pedals than when you sit down. The effective pivot point is _behind _the BB. But of course that doesn't matter if your brain shuts off when you see an acronym.


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## Lelandjt (Feb 22, 2008)

Have you ever ridden a bike with a concentric BB pivot or really low and rearward pivoting URT? Those bikes have no anti-squat and that's why they bob when pedaling out of the saddle. High or forward URTs fight this a little by placing a greater percentage of your weight on the swingarm.
This bike is a URT and has no anti squat. Moving the pivot behind the BB changes the direction the BB moves but doesn't add any chain growth or anti-squat. The only riders asking for bikes with no chain growth are single speeders (even then only the ones who don't climb) cuz everyone else likes at least some anti-squat.
If you're intrigued by this concept of a URT with the pivot behind the BB look at GT's suspension and how the BB moves. It's a pretty good system that gives the rearward axle path of this bike but with just the right amount of chain growth and BB movement.


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## andrepsz (Jan 28, 2013)

I think I can put that on Solidworks and create an assembly to finally see this thing working! With time ...some day I'll do it


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## andrepsz (Jan 28, 2013)

Just did this animation on SW...crude way to show this...but here is the swing.

Looks like pretty good engineering to me. BB almost stays in place






Detail on BB:






Or....I just found out that this setup has a great potencial to be a cool monocycle with suspension...including handlebar! 

...but I would put the saddle on the steerer and handlebar on the seat tube...makes more sense looking at the swing.






With all my respect for the creators of this frame, I'm just having a little bit of creativity exercise:






Yep....I got nothing else to do this morning.

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## Procter (Feb 3, 2012)

Great analysis Andre. I looks like the bb comes up about 2 inch towards the end of the compression. That can't feel good. There is a pinkbike article from sea otter which says it's 180mm travel. Can you stop the wheel at 180mm and see if the vertical bb displacement initiates before or after 180mm of wheel movement?


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## NWS (Jun 30, 2010)

Yeah, I'd expect the suspension to stiffen towards the end, maybe by a lot. 
Thanks for mocking this up, Andrepsz. Would that software plot BB travel over wheel travel? 
I wonder how much travel you'd get before the effective spring rate gets, say, 10% higher.


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## NWS (Jun 30, 2010)

Lelandjt said:


> Have you ever ridden a bike with a concentric BB pivot or really low and rearward pivoting URT? Those bikes have no anti-squat and that's why they bob when pedaling out of the saddle. High or forward URTs fight this a little by placing a greater percentage of your weight on the swingarm.
> This bike is a URT and has no anti squat. Moving the pivot behind the BB changes the direction the BB moves but doesn't add any chain growth or anti-squat. The only riders asking for bikes with no chain growth are single speeders (even then only the ones who don't climb) cuz everyone else likes at least some anti-squat.
> If you're intrigued by this concept of a URT with the pivot behind the BB look at GT's suspension and how the BB moves. It's a pretty good system that gives the rearward axle path of this bike but with just the right amount of chain growth and BB movement.


There's a DJ park in my area that rents P-Slopes, I did that a couple times before building a Morpheus Skyla to use instead. I'm not a fan of the P-Slope.

I just think it's hilarious that attaching the BB to the swingarm stiffens the rear end, pivot placement doesn't matter... and the P-Slope squats. You see the problem?

For the record, I do believe _one _of those things. 

I have a Canfield Jedi with a very rearward axle path, and I like it a lot. Was hoping GT would make a 180mm 26er but it looks like that's not happening.


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## andrepsz (Jan 28, 2013)

Procter said:


> Great analysis Andre. I looks like the bb comes up about 2 inch towards the end of the compression. That can't feel good. There is a pinkbike article from sea otter which says it's 180mm travel. Can you stop the wheel at 180mm and see if the vertical bb displacement initiates before or after 180mm of wheel movement?


I literally took that first pic and draw each part over it, so it's not on real scale right now. I would need to know the precise dimensions on the frame to scale this model right, then I could do that. 
Well, I could eyeball the wheel size or some other reference but wouldn't be 100% accurate.

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## andrepsz (Jan 28, 2013)

NWS said:


> Yeah, I'd expect the suspension to stiffen towards the end, maybe by a lot.
> Thanks for mocking this up, Andrepsz. Would that software plot BB travel over wheel travel?
> I wonder how much travel you'd get before the effective spring rate gets, say, 10% higher.


Didn't really get your question? Spring rate 10% higher...from what reference?

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## shupack (Nov 28, 2012)

the unicycle looks like fun...


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## Lelandjt (Feb 22, 2008)

NWS said:


> There's a DJ park in my area that rents P-Slopes, I did that a couple times before building a Morpheus Skyla to use instead. I'm not a fan of the P-Slope.
> 
> I just think it's hilarious that attaching the BB to the swingarm stiffens the rear end, pivot placement doesn't matter... and the P-Slope squats. You see the problem?
> 
> ...


Well it only stiffens the suspension proportionally to how much weight you lift off the seat and it's related to the distance and direction between the BB and pivot (BB travel path relative to gravity and leverage). Most non-Walmart URTs used a fairly high and forward pivot to increase the stiffening effect (and get that great bump eating axle path). This was neccessary to counter act pedal bobbing due to the lack of chain growth/anti-squat.
I'm inclined to think that using an idler like Canfield rather than a moving BB like GT is a better way to manage chain growth with a high pivot.


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## andrepsz (Jan 28, 2013)

Procter said:


> Great analysis Andre. I looks like the bb comes up about 2 inch towards the end of the compression. That can't feel good. There is a pinkbike article from sea otter which says it's 180mm travel. Can you stop the wheel at 180mm and see if the vertical bb displacement initiates before or after 180mm of wheel movement?


So I did my best to put that line on the back at 180mm:





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## NWS (Jun 30, 2010)

andrepsz said:


> Didn't really get your question? Spring rate 10% higher...from what reference?


As compared to the effective spring rate when the suspension is at zero travel. Or maybe as compared to whatever the effective spring rate is when the suspension is at the sag point.

I'm sure the upward movement of the BB translates to an increase in the effective spring rate if the rider's weight is on the pedals, and I wonder by how much. I think that plotting BB movement over wheel travel, would make it easier to interpret. Or perhaps better yet, plot the ratio of frame-movement/BB-movement (still with wheel travel on the X axis). It's 1:1 on a regular bike, and in the early stroke on this bike, but it looks like 1.5:1 at the end of the stroke. Which I'm guessing would increase the effective spring rate by 50% or so. Which would not be cool.

Plus there's the funky linkage around the shock, but from that last video it seems like the leverage ratio stays fairly constant. (Plus there's Boyle's Law happening inside the shock...)


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## andrepsz (Jan 28, 2013)

How about this one:
Vasttech - Vast Tech most efficient and advanced full suspension system


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## andrepsz (Jan 28, 2013)

Just found this cool simulation on youtube on this frame:


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## Jayem (Jul 16, 2005)

NWS said:


> With concentric single pivots the BB is also part of the swingarm.


No, pivoting about the BB and being part of the swingarm are two different things. If you take the swingarm off the bike, where is the BB? It's on the main-frame. Storm H2, Trek Y, Ibis Sazabo, etc, these are all examples of URT. Rotec, early Lenz bikes, Profile DR1, these had concentric pivots.


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## Jayem (Jul 16, 2005)

andrepsz said:


> Just found this cool simulation on youtube on this frame:


They forgot to mention: "Most highly loaded pivots ever" in the benefits section.


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