Did You See That? RAM Bikes URT Chassis and Quadrilateral Fork - Sea Otter 2015
Richard Sheppard is six foot, six inches tall and weighs in at 289 pounds on a good day, so as one may expect, there are not many dual-suspension trailbikes out there that can either fit him, or that can manage to perform well enough to make him happy. Sheppard also prefers the durability and simplicity of a single speed, which further reduces his shopping list - and eventually led him down the path to making his own bikes. To that end, Sheppard founded Ram Bikes a number of years ago and his latest creation is an efficient-pedaling one-speed with seven inches of wheel travel on both ends. Like all of his designs, it is both wild looking and functional, and he'll make you one if you say please. Although he considers frame building as a hobby, a steady stream of like-minded customers may eventually force him to take up the TIG torch full time. Sheppard dropped in to the Pinkbike Dome at Sea Otter to show us his latest masterpiece.
![RAM bike and fork]()
Ram Bikes URT Chassis
The RAM chassis is essentially the same as the old-school unified rear triangle designs of the mid 1990’s. The bottom bracket is attached to the swingarm, which in the case of this design, pivots on a four-bar linkage near the intersection of the seat tube and top tube. The advantage of a URT design is no-bob pedaling when the rider is attacking out of the saddle. Sheppard says that, while most observers believe that the bottom bracket's vertical travel is excessive, the four-bar linkage is configured instead to move the BB fore and aft so that it does not overtly affect pedaling.
There is no front triangle. Instead, a single, large-diameter chromoly pipe connects the fork to the swingarm, creating a chassis that looks about as simple as a dual-suspension design can be made. Reason two for the RAM's unified rear end is that the chain length is stable through the suspension's travel, which means that Sheppard's design is well adapted to single-speed applications. For geared riders, no chain growth means that a mid-length derailleur cage should be enough to handle any one-by drivetrain.
![RAM quadrilateral suspension fork]()
![RAM quadrilateral fork]()
![RAM fork]()
Be sure to check out all of our Sea Otter Classic images in this gallery.
Ram Bikes URT Chassis
The RAM chassis is essentially the same as the old-school unified rear triangle designs of the mid 1990’s. The bottom bracket is attached to the swingarm, which in the case of this design, pivots on a four-bar linkage near the intersection of the seat tube and top tube. The advantage of a URT design is no-bob pedaling when the rider is attacking out of the saddle. Sheppard says that, while most observers believe that the bottom bracket's vertical travel is excessive, the four-bar linkage is configured instead to move the BB fore and aft so that it does not overtly affect pedaling.
There is no front triangle. Instead, a single, large-diameter chromoly pipe connects the fork to the swingarm, creating a chassis that looks about as simple as a dual-suspension design can be made. Reason two for the RAM's unified rear end is that the chain length is stable through the suspension's travel, which means that Sheppard's design is well adapted to single-speed applications. For geared riders, no chain growth means that a mid-length derailleur cage should be enough to handle any one-by drivetrain.
RAM's 180mm quadrilateral suspension fork weighs about six pounds.
RAM Quadrilateral Fork
Sheppard's coup de grace this year was a 180-millimeter-travel leading-link suspension fork borrowed from a similar motocross fork design by Valentino Ribi. The fork uses a four-bar linkage to create a nearly straight axle path which traces the head angle within an eighth of an inch (4mm). As a result, the quadrilateral fork feels and steers like a conventional telescopic design with the exception of one important aspect: it has much less stiction.
The linkage pivots run on small-diameter, smooth-acting ball and plain bearings, while suspension and spring duties are handled by a single Fox Float X Kashima CTD shock. The smaller swept area of the shock and the fact that the quadrilateral fork drives it at bit more than a two-to-one ratio helps reduce starting friction and reportedly, makes for a much more responsive fork.
Four-bar forks are neither new nor revolutionary, but in the context of the RAM project, it makes sense, especially considering that Sheppard shreds long descents like the Downieville DH on a regular basis, so he needs a responsive, long-stroke fork that can take a beating. The uppers and lowers are chromoly steel, while the articulating links are water-jet cut aluminum. Down below, the massively wide front hub is actually two Azonic front hubs, cut down and joined at the center so Sheppard could use two disc brakes. A splitter beneath the fork "crown" sends brake fluid to both front brakes from the left-side lever. There is no welded or mechanical joint to transfer braking torque from one side of the fork to the other. Instead, the left-side spokes handle the torque of the left side brake and the right side spokes take care of braking on the right. Sheppard said: "I discovered that one brake heated up too much on the longer descents, so I added the second brake. Now I never worry about heat at all."
Sheppard's coup de grace this year was a 180-millimeter-travel leading-link suspension fork borrowed from a similar motocross fork design by Valentino Ribi. The fork uses a four-bar linkage to create a nearly straight axle path which traces the head angle within an eighth of an inch (4mm). As a result, the quadrilateral fork feels and steers like a conventional telescopic design with the exception of one important aspect: it has much less stiction.
The linkage pivots run on small-diameter, smooth-acting ball and plain bearings, while suspension and spring duties are handled by a single Fox Float X Kashima CTD shock. The smaller swept area of the shock and the fact that the quadrilateral fork drives it at bit more than a two-to-one ratio helps reduce starting friction and reportedly, makes for a much more responsive fork.
 | I discovered that one brake heated up too much on the longer descents, so I added the second brake. Now I never worry about heat at all. |
Four-bar forks are neither new nor revolutionary, but in the context of the RAM project, it makes sense, especially considering that Sheppard shreds long descents like the Downieville DH on a regular basis, so he needs a responsive, long-stroke fork that can take a beating. The uppers and lowers are chromoly steel, while the articulating links are water-jet cut aluminum. Down below, the massively wide front hub is actually two Azonic front hubs, cut down and joined at the center so Sheppard could use two disc brakes. A splitter beneath the fork "crown" sends brake fluid to both front brakes from the left-side lever. There is no welded or mechanical joint to transfer braking torque from one side of the fork to the other. Instead, the left-side spokes handle the torque of the left side brake and the right side spokes take care of braking on the right. Sheppard said: "I discovered that one brake heated up too much on the longer descents, so I added the second brake. Now I never worry about heat at all."
A T-splitter zip-tied to the fork below the Float X shock routes brake fluid to the twin calipers. A pair of threaded shafts determine the fork's axle path. The tubular chromoly bits carry the major loads.
The massively wide front hub is actually two hubs sliced in half and rejoined, so Sheppard could have a six-bolt rotor interface on both sides. For stiffness, he uses a 20-millimeter through-axle.
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It's an overly-complicated VPP thudbuster.
Then imagine taking any other suspension design, stand on the chain stays, and tell me how the suspension will compress.
Its the same thing.
You need to replay the video or pause it and slowly click through frames, but this shows how the bb and rear axle move. www.youtube.com/watch?v=DLLzyInE3oY
That would also actually increase the odds of going OTB: frontwheel more to the back means smaller leverage.
I'll just stick with normal forks
Radrider's comment about pivoting around the BB is probably the most insightful thing on this whole page.
The marketing in this industry seems to have convinced an awful lot of people that buzzwords are all you need.
My Saint is an outstanding brake..but I'd try a dual setup, just sayin : )
www.retrobike.co.uk/forum/download/file.php?id=26102
Dual disc fork and hub... though I don't know if I'd roll the dice with a DNM fork. It's one thing shelling out $80 on a cheapo air shock, but $600 is on a whole different level.
and this: www.amazon.com/DNM-Mountain-Dropper-Seatpost-30-9x330mm/dp/B00K2PFE9K/ref=sr_1_1?ie=UTF8&qid=1429715285&sr=8-1&keywords=dnm+dropper+post
I understand that racers wouldn't want this due to extra weight and shit, but for the average rider who hits bikeparks and DH purely for their own pleasure, why not?
Anyway, I hope to see more people trying to make that practical. This is a start. I believe in it!
In this design the rear triangle seems to move forward as the suspension compresses. I'm having trouble imagining how that would track over anything. I would love to see a video of someone riding it.
If you could make a bike that had a whole bunch of seated suspension and comfort but was like a hardtail part of the time wouldn't that be great? That was the original driving thought of URTs when they were around. People were stuck much harder back then on the idea that suspension was heavy, bad pedalling and only for descending (which was sort of true given the bikes at the time) so URTs were a marketable concept. Many people are happy riding bikes with zero rear suspension.
Actually, just found a Video of it shown in Linkage (Suspension geometry design tool) www.youtube.com/watch?v=DLLzyInE3oY
But the problem was not caused by URT itself, it was caused by the ridiculous pivot placement on those old URT bikes.
This bike has an effective pivot point near the BB, so it should ride like any other bike with a similar pivot point. If you stand on the pedals and bounce, the BB will drop just as much as any other bike with the same wheel path and the same effective spring and damping rates - regardless of where the actual pivots and links are located.
When this guy wants to upgrade, he designs and builds what he wants.
Compatibility is for consumers. He's a builder.
It's crazy that this guy isn't building with bigger wheels. 29" wheels are to 6'6" as 26" wheels are to 5'6".
I'm 6'6" 220. There are bikes that fit, and big wheels and tall head tubes are key. Specialized Enduro 29 in XL is massive; put a CCDBA on there and you have a large person bike that is eminently durable, stiff and good pedalling. The Yeti SB6 also comes in an insanely big XL.
I'm not sure what the problem with fork stiction is? As a bigger rider I've always required a lot of preload and then more compression damping to my forks. Yeah I get that those things shouldn't come from the seals but at the end of the day it's still providing the resistance you need. Avoiding stiction and then introducing flex through those linkages doesn't seem like a good trade for a 290lb rider.
That all being said I still love this stuff. I would love to try this bike. I actually kind of want the frame regardless - but can I get just the frame and with a derailleur hanger?
I wonder if it would stinkbug the way some URTs did?
Yeah. We're going to need a video.
Actually, just found a Video of it shown in Linkage (Suspension geometry design tool) www.youtube.com/watch?v=DLLzyInE3oY
But I see, this is America. Obese people rule.
Nonetheless a very impressive vehicle. Can it be retrofitted with two 25kw electric engines?
6'8" here, there's not many bikes which fit, so I tend to remember the ones which do. The remedy is massive.
www.mondraker.com/15/eng/bikes/crafty-xr/400/geometry
I so intrigued and fascinated that my bike would have a mechanical out of spite and jealousy for sure.
Even if I never rode her,the curious intention is enough to get me in trouble!
They're only useful for people who ride seated ALL THE TIME.
Like this slopestyle bike, for example:
www.specialized.com/us/en/bikes/bmxdirt-jump/pseries/pslope-frame
MIND = BLOWN?
www.pinkbike.com/news/the-short-turbulent-life-of-urt-suspension-mtb-history.html
&
www.pinkbike.com/news/throwback-thursday-5-weird-and-wonderful-products-from-sea-otters-past.html)
Consider 2, almost identical frames, with the same front end (main frame), the same rear end (suspension arm) and one suspension pivot located at the BB tube. Here is the only difference:
A) The first one (let us call it the “A” frame) has the BB welded ON the rear arm. The BB is enclosed within a pair, of so beloved, bearings, which are attached on the main frame, via the old ring & bold apparatus.
Now,
This is CLEARLY a URT, isn’t it? The BB is part of the rear suspension arm….
B) The other one (we will call it the “B” frame) has the BB welded ON the main frame (that’s the front part of the frame!). The BB is enclosed within the same pair of bearings, which are attached on the rear suspension arm via the old ring & bold apparatus.
Now,
CLEARLY this is NOT a URT frame! The BB is part of the main frame and not the rear suspension arm.
The difference will be more evident if we took apart those 2 frames. The “A” frame will be a URT (the BB is part of the rear suspension arm & the “B” frame will not be, as the BB will “stay” on the main frame.
Here are the questions.
1) Given the fact that those 2 frames are equipped with the identical parts (suspension fork, parts, brakes…) will they ride differently?
2) If we cover the pivot, will anyone be able to recognize which witch is which, by just ridding the damn things?
3) So, given the fact that a URT may ride exactly the same as a non URT, just because both frames suspension arms are pivoting on the same axle, cannot we claim that if we are able to rotate an other URT design concentrically to the BB, it will ride as a non URT?
Or more correctly,
With this principle, won’t we be able to get rid of the stiffening of the rear suspension while descending, as soon as we stand on our pedals?
This is what the RAM bike does. The rear arm is suspended over a virtual point that is also the BB. So when the rider stands on the pedals the rear end does NOT stiffen!
This has nothing to do with the preferred suspension travel. In this apparatus, the wheelbase gets shorter as soon as the rear wheel axle crosses the BB height. At first and as long as the rear axle has not passed the BB, the wheelbase will increase. Then as the suspension arm travels through to the limits of it’s travel, the wheelbase will shorten.
For my (a personal preference) this is the only negative with Mr. Sheppard’s design. Everything else is brilliantly made! For once more congrats Richard!
How many of us have welded up a frame? Most of us barely understand how suspension works and this guy up and made his own bike. I pretty sure he has a better handle on how it works than we do.
Bravo, man!
But they will say their the same "it will not work"_bullshit because they just UNABLE TO VISUALIZE THE CINEMATICS of this suspension nevermind how much you describe it to them. Just look.
So don't waist your time and energy too much.
You (and several others) told the main thing already: THE BOTTOM BRACKET ***AND THE RIDER**** ARE SUSPENDED!
It is enough to stop be a dumb telling "it will not work".
The rider "hangs" on the shock, what more to understand ?
HOW SUPPLE - it is the other question.
The suppleness and sensetivity of this design depends on a shock probably more than other designs (BB_ON_FT). That''s why the creator designer used CCDB - because it is dramaticaly tunable and versatile.
I bet CCDB will manage this situation very well, but of course the adjustments will differ from those used for "BB_ON_FT" designs.
If to use some other simpler shock the result will likely be less sensetive and supple.
I'm personally glad to see there is at least one guy who understands, and if there are more than one of them here - I'm happy, Im not alone!
But when I see such veichles I'm full of enthusiasm!
dirtmountainbike.com/features/the-15-worst-mountain-bike-products-ever.html/16#XVMbXfc2MWvSerP2.97
singletrackworld.com/forum/topic/what-are-urt-bikes
www.oocities.org/bezean/fullsus.html
let me quote a part of the last link
"The inherent problem with this design is that the rider is in effect standing on the swingarm. This is less of a problem when the rider is seated, but the natural tendency when going over larger obstacles, rough terrain, or technical sections is to stand up, rendering the rear suspension almost useless."
so dry your pants and next time be a little less prone to scoff as dumb someone else's comment.
You and others "non-understanders", please, understand that NOT VERTICAL FORCE IS APPLIED to the rear wheel but BACKWARD-VERTICAL because a bike moves forvard.
And consider this design do not forget the rider's weight on the BB helps to rotate all the swing-arm when the hit force is applied to the rear wheel because the rear wheel is lighter and on the "lever" to the BB.
Moreover, here the BB IS THE PIVOT, as it is mentioned several times, so hit force is "converted" to rotarion around the BB, means AROUND THE MAIN WEIGHT, and this is just another deal.
"But that ICR stuff makes a 6” travel bike pedal like a 2” travel bike, so that’s progress." now either this is bullshit or the suspension sucks at doing its job, because we are talking about a downhill bike with 6 inch travel that pedals better than a modern XC rig. now i believe that with this design the pedal bob is lessened to a very good extent, but not for a second i will believe that it is also active and responsive like an Horst or VPP / DW design. you can't have a drunken wife and a full bottle of wine. try to huck to flat that thing over a 3/4 meters drop, guess your ankles will not be happy. props to the guys that welded the frame by himself, i'm not denying that it's a very nice work. i'm only pointing out the obvious.
Man, after looking at visualized cinematics in this video "youtu.be/DLLzyInE3oY" it becames OBVIOUSLY that in this design RIDER'S WEIGHT APPLIED TO THE BB ***HELPS*** the swing arm to rotate around the BB, thus making this rear suspension very responsive, especially with CCDB installed.
fstatic3.mtb-news.de/f3/16/1699/1699091-wnnb0np74owh-cm0a9719-original.jpg
Do you know tire name/model on the rear wheel at this pic: fstatic3.mtb-news.de/f3/16/1699/1699091-wnnb0np74owh-cm0a9719-original.jpg ?
Unified Rear Triangle = URT
Show us please, the REAR TRIANGLE and it's UNIFICATION in this particular design.
And the examples of "Most poor performing URT that people remember were the opposite of this as they were built long before we had platform valving"
in the studio, please.
Some people just can't get rid off of the tags and patterns in their heads once got used to some terms and abbreviations.
URT's have a HIGH PIVOT, much higher than BB - well pedalling sitting but not much supple standing.
And this design has a low pivot around the BB.
If you can't see that this bike is a URT I really don't know what to say other than you don't know what URT is.
A URT design is a suspension bike where the BB is directly fixed to the rear axle- all URT designs share this particular characteristic, regardless of the pivot location (either fixed or migrating instantaneous center of rotation.) The RAM bike featured here has the BB directly welded to the rear dropouts and they move together- it's a URT because the chainstays and the BB are the swingarm/rear triangle. URTs can be simple swingarm designs or they can be multi link designs.
I have no idea what "in the studio, please" means but I stand by my statement. More on that in a bit...
Contrary to your last statement, not all URTs have a high pivot. The pivot can be located high and forward- the most often thought of Sweet Spot design patented by John Castellano and used by Schwinn, Ibis, WTB and a few other manufacturers and this is what most people think of when they talk about a poor performing URT. Contrary to your last statement, not all URTs have a high pivot. There have been many URTs built with low pivots, pivots around the BB as well as multi link designs.
The only way to get an active URT design is to have the pivot laterally located near the rider's center of mass- this is because of how a URT responds to mass transfer. As the rider's mass moves forward over the pivot point the bike will squat under pedaling- the closer the pivot is to the BB the worse this will be because of how the rider's mass is coupled to the swingarm/rear triangle. In a URT design the rider is both a sprung and unsprung mass, depending on the position of the rider (seated or standing.) The distance and location of the pivot relative to the BB dictates how the rider's mass affects the suspension action.
That's exactly my point. The high forward pivot URT bikes were effectively a rigid bike when you were standing- the majority of your unsprung mass is located well behind the swingarm pivot and the suspension is not active at all. If you make the pivot close to (or around) the BB the majority of your mass is much closer to the pivot (if not forward of it) so the bike is much more active but it will squat under acceleration (pedal poorly) because your forward weight transfer causes the suspension to compress- there is no way around this so that's why I say you need a fair amount of low speed compression damping (a low leverage ratio helps too.) The reason why we didn't see very many URTs back in the day that had pivot placements that were conducive to having active suspension was because we didn't have the type of damping necessary to make them work- they would have pedaled horribly.
Having said that URTs will never be a high performance solution, reason number one being the unsprung mass is too high. But not everyone needs a super high performance bike- some people have very specific design parameters that a more modern URT design may fulfill and if works for them and they're happy then who am I to criticize them...
Am I right?
to answer your question:
"Why not?"