the URT is back

JEJames had one of those concentric linkage Edge frames hanging up in the Bramall Lane shop for ages, always wondered what happened to it once it went.

what happened to it once it went

It weighed so much it caused a China syndrome.

what happened to it once it went

I heard it was launched into space because it was causing the earth to tilt.

Did nobody notice the dirty great big picture at the start of the article??

one of the nicest looking gearbox (and indeed FS) bikes i’ve seen in a while.

Did nobody notice the dirty great big picture at the start of the article

Yes, but this thread is about the URT one.

TBH I don’t think its fair to slag off URT designs.

it is if they are still trying to make them work years and years after they were deemed to be rubbish

You can’t just make things cheaper

Yes you can, it happens all the time, the motor car used to be the preserve of the stunningly rich, now every chuffer owns one, there are loads of similar examples.

Just because someone says something “Should” be expensive doesn’t make it so…

OK the concept is a bit novel (but not without precident) that doesn’t mean it needs to cost the earth. Whoever manages to get a sensible weight, sensible range gear-box solution to market at a price where customers don’t need to have sold a kidney to buy it then they will clean up.

yeah the car used to be expensive then over 100 years later it became cheaper… excellent reasoning there, it didnt just appear cheaper.

like anything you have to make the expensive ones before the cheap ones come out.

superfli – Member

URT will never work as FS as you are not suspended from the rear wheel! The BB is attached to the rear triangle and rear wheel, therefore if you are standing on the pedals, you are in effect, standing on the rear wheel ie, not suspended.

That’s not true. You need to look at the whole bike. Imagine a URT rear end and a rigid fork, dropping out of the sky with you on it, standing up. When you land, the suspension will still compress. It’s hard to visualise in the usual terms of “suspension goes up” so try imagining the bike as a hinge- it’ll bend in the middle, and your feet being at the end of the swingarm, near the hinge, will move down relative to the wheels.

Not that this encourages me to buy a URT bike today. Heh, there’s one in the garage actually, maybe should take its 45lb bulk out for a thrash.

It won’t compress, you aren’t exerting a force on the front half of the frame no matter where you drop the frame from.

The only effect on the front would be it’s own momentum, which isn’t a real life scenario

Or as your weight pushes down rotating about the front and rear hubs but again the leverage ratio for that to happen would render the frame useless in normal conditions

thepodge – Member

It won’t compress, you aren’t exerting a force on the front half of the frame no matter where you drop the frame from.

You can’t not exert a force on the front half of the frame, without unbolting it from the back. Your weight isn’t directly over the rear wheel, it’s on the end of a lever that runs about 1/3d of the wheelbase of the bike so there’s a significant force on the front (complicated a bit by BB and pivot location, obviously)

The maths is beyond me, so for this stuff I’m falling back on being old and remembering. The yoof may wish to visit halfords.

TBH I don’t think its fair to slag off URT designs.

it is if they are still trying to make them work years and years after they were deemed to be rubbish

I don’t deny that 🙂

Ok, ignore my first sentence and read the other two.

While a force is exerted, the counteracting forces or the shock and the leverage ratio of where the pivot is located over power the minimal force on the front.

Pop out now and ride up a curb with you stood on the chainstays and see how much difference it makes to standing on the pedals

Er, your test makes a lot less sense than “Ride a URT bike and see what happens”.

I don’t have a urt frame to hand, do you? That is the simplest way to create anything like a urt without one

I have had one I’m the past, the Orange, it was ok for blasting up hills, mashing the pedals and then coasting back down the hills seated but that was about it

My point still stands, with a urt you do not exert enough force on the front of the frame because you’re not suspended between the suspension systems, you’re suspended on one of them

PS. IR. You have mail

First I thought – that’s a really nice looking bike.

Then I scrolled down.

What the jiggery fu…?

That is the simplest way to create anything something which works nothing like a urt without one

FTFY

Rreally, that’s the best you can come up with?

With a urt your feet are directly connected to the same structure as the rear wheel with the pivot in front of you. Riding a full suspension with your feet on the chainstays is the simplest way of recreating that. It’ll give you the basic principles, at least more than “this is what happens but the maths is beyond me”.

I know what it reminds me of:

http://www.castellanodesigns.com/Zorro.html

based on the old Schwinn Sweetspot design.

Pivot looks to be in the same position

Fact is, youre weight is not suspended with a urt design whilst standing. You are not on a frame that is suspended by two shocks to the wheels. You are stood on rear triangle

The rider is not isolated from rear axle impacts on the Moongoose or GT either. Both totally pointless desings that actually do the opposite of what the companies state.

Simplist take on the URT (IMO):

Think of the swingarm as a simple lever, riders mass when stood up is applied at a point much closed to the pivot than the rear axle which under compression moves relatively less than the rear axle, but of course you are still on the same frame member so while you are not utterly removed from rear axle you are experiencing less of the impact/vibration(s).

When seated more of the riders mass is applied direct to the pivot actually making the swingarm more “active” but pedaling a bit more of a bouncy affair, firm up the spring to make the seated behaviour of the frame more acceptable for pedaling and you knacker the out of the seat operation of the suspension.

If you look at the extreme example of a URT; the ST10 that is realistically going to see most of its use with the rider out of the seat, and hence is normally sprung a lighter than an equivalent “Fully Active” design might be. It delivers some key advantages; simplicity, Zero chain grow (so could be SS’d, Alfined, geared), less pedal bob (When stood up) and arguably more “Feel” for the back wheel. But of course it’s not perfect (no bike is) when seated the suspension will behave very differently, where and active design will be a bit more consistent across all rider positions, it works in that instace as the bike has a rather specific purpose, but for an “AM” or XC bike where climbing and descending performance are both important a URT might well not get the balance of compromises quite right…

The GT/mongoose I-drive type designs might appear URT-esq but they are in fact designed specifically to articulate the BB and separate it from the rear axle/swingarm motion, it ain’t a URT and it isn’t a single pivot, faux bar or Horst type design, it’s something different again.

Sort of…
It’s not so much the weight being on the pivot as the fact that you are not suspended between, but on the moving parts. Plus you have very little force acting on the front so the rear has nothing to work against.

I agree that the GT and similar designs shouldn’t be classed as a urt

i have one issue with that gearbox, imagine the pain and expense if the crank seals are on a par with HTII.

These things always make me laugh.

They claim its better because a rear mech always gets knocked off by rocks.

Thay claim it better because a rear mech puts weight in the wrong place.

They forget to think how much a rear mech weights (bugger all) and how much it costs (bugger all) and how little you do knock them off (maybe once ever five years or so)

Then of course when you read the small print you find you cant change gear under load with this gearbox. You have to use grip shift. They dont mention how much it weights (more that all the rear mechs you have ever owned) they dont mention how much oil you need to stop it grinding into metal paste and they dont mention how expensive it is to replace a worn gear. Oh and I bet you wouldnt want to ride it through a puddle. Not to mention the URT idea – idiots.

Leave gearboxes to motorcycles or cars (which do have a clutch)

Very negative and uninformed view there.

Been thinking about the URT again, I can see where it came from, usign a very simplified method of mechanically locking out the shock just by shifting your weight. But the downside is the suspension is only active when seated, and completely inactive when standing, you can’t have it the other way round, which new shocks and more thought into suspension design now allows.

Trimix, you’re saying the Rohloff Sspeedhubs are a bad idea? You ever used one? If people didn’t think of alternative methods of doing something, the world would be a very boring place.

I bet you wouldnt want to ride it through a puddle

Yeah, cos motorbike gearboxes aren’t waterproof either are they? And chainrings and cassettes never get gunked up with mud or snow/ice.

Sheesh, bring on the naysayers and doom-mongers 🙁

have a look at this vid:
http://www.spiegel.de/video/ueber-den-himalaya-haertetest-fuer-die-pinion-schaltung-video-1081252.html

specifically around 40 seconds to see a Pinion in a “puddle”

Riding a full suspension with your feet on the chainstays is the simplest way of recreating that.

Except that if you do that you’re putting the load far closer to the rear wheel and far further away from the pivot than in the case of a real URT. The distance from pivot to load is several times what it is in a real URT. The difference between that and a real URT is likely to be more than the difference between a 4-bar Horst Link and a URT, hence a pretty useless way to judge how well URT works.

I stand by my fix.

should do a kona A/cove Gspot design. URT’s are megashit.

G-Spot doesn’t have adjustable dropouts.

the A does though

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DSC_0289[/url] by ir_bandito[/url], on Flickr

i was refering to the min pivot round the BB, but nice photo.

Yes, I’m going to stick with megashit then people with little better to do can try pull that apart too.

However, is it wrong that aesthetically I really like the look of the castellano linked previous?

My Absolut sx doesn’t have adjustable dropouts (well you can buy them but they are horizontal and £60 per side) so I knocked up a simple tensioner that hides behind the chainring

Haven’t ridden an i-drive but haven’t the Atherton’s all been significantly more successful on their i-drive GTs than they were on their Commencals which suggest they might not be complete cr4p?

Haven’t ridden an i-drive but haven’t the Atherton’s all been significantly more successful on their i-drive GTs than they were on their Commencals which suggest they might not be complete cr4p?

No. Gee was 1st placed WC and World Champion on the single pivot Commencal. However, He has had some massive offs on the GT semi unified bike.