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They were claimed to eliminate pedalling dead spots — but did they work?

Image: PMP cranks by robadod from LFGSS

We take a look at one of the more bizarre technical aberrations of recent history: the wackiest cranks ever made.

In 1981 Cycling Weekly magazine published a favourable review of an unusual new crank. The magazine gave a set to “a first-category Surrey roadman to try them out.”

The write-up said: “He fitted them in March and although our test is now over they are still on his best road bike. He has come to prefer them to orthodox cranks.”

CW’s tester “enjoyed the ‘feel’ of the cranks and reported that the slower his pedalling speed the more advantage he felt, which is perhaps why they are finding favour with big-geared time triallists.”

The tester told CW: “I didn't just get the power on the downward strokes of the pedals but all the way round the pedalling revolution as at low pedalling speeds dead centre seemed to be removed. This helped me keep a steady rhythm particularly when sitting back in the saddle climbing hills.”

He didn’t feel the same benefit when pedalling quickly in a low gear, though.

CW concluded: “So there is the verdict, whatever the theories, in practice our roadman tester felt the PMP cranks offered an advantage – and surely that is the true criterion.”

PMP crank B&W.jpg

An early publicity shot of the PMP Brevettato cranks   

That crank was the PMP Brevettato. Its unusual (but, as we’ll see, by no means unique) feature was a right angle bend about a third of the way between the bottom bracket axle and the pedal.

PMP made some interesting claims about the Brevettato cranks. They included:

  • The unique form of the PMP pedal crank means improved distribution of the energy required in pedalling and a perfectly round stroke; the result: increased equilibrium.
  • Its L-shaped design increases the pedal's propulsion power and lessens energy dispersion on the downstroke.
  • Pedalling the PMP way means to be perfectly in the saddle; in fact, the bicycle rider is forced to lean back slightly more than usual, putting him in the best possible aerodynamic position.
  • The PMP pedal crank means that pedalling is no longer an "ankle game" since the bottom dead-point is lightened to allow greater ease on the upstroke.
  • Bicycling becomes a pleasure and not a chore because the PMP pedal crank and its unique features take away the exertion and lighten muscle strain.

Bold claims, and with Cycling Weekly’s Surrey roadman finding they eliminated dead centre, you have to wonder why the design isn’t now ubiquitous.

PMPcranksadvert.jpg
An ad for PMP cranks.

That’s simple: it’s all bollocks.

A crank is a lever. The torque you generate when you load up the end of a lever depends on just two things: the force you exert and the distance between the point where that force is applied and the pivot.

Nothing else matters, especially not the route the lever takes between the two points. It can be a straight line, a right angle bend or any other shape; it doesn’t matter. All you achieve by making a crank any other shape than straight is to add weight and flexibility.

PMP cranks were even marked with the distance between the crank and pedal holes. As the Bicycle Museum of Bad Ideas remarks: “somebody at PMP understood it was simply an odd way to make a 175mm crank”.

Pretty much everyone who was paying attention in physics at school pointed this out at the time, but that didn’t stop a fad for PMP Brevettatos, especially among time triallists.

Even the great 80s time triallist Ian Cammish used them. Cammish, who won the Best British All-Rounder contest nine times in the 1980s, mentioned them when he tried to sell one of his 1983 bikes on eBay in 2013.

“Unfortunately the PMP cranks cracked a long time ago,” he wrote.

They had a bit of a reputation for that, though to be fair so did many other high-end cranks of the era.

Perhaps because of these reliability issues, and because not many were made in the first place, PMP Brevettato cranks are now rare and collectible. The most recent set I’ve seen on eBay went for US$400 — almost £300.

Other wonky cranks

The bike industry has a serious problem with knowledge loss, which leads to people who really should know better reinventing bad ideas over and over. The PMPs weren’t the first non-straight cranks (the earliest seem to have been in 1897), nor the last. Like the monster lurching back to life at the end of a bad horror movie, wonky cranks keep coming back.

Want to make people go “What the hell?” get yourself a set of dpardo Sickle Cranks:

dpardo r58 cranks.jpg

It’s not at all clear what advantages dpardo claims for this design. PMP had a slight case of ‘Campagnolo spoken here’ Italglish, but dpardo really needs to get a native speaker of English to write its marketing copy. It says — and I swear I haven’t changed a letter of this:

58T gear turns once is 1.6M faster than 50TAs same as pedaling 50T Same pedaling force pedal 58T, the riding performance is 16% increasing than 50T with normal cranks

The craziest recent reappearance of wonky cranks has to be Z-Torque cranks, which came and went between 2010 and 2014.

Z Torque cranks.jpg

The shape was claimed to have come to inventor Glenn Coment in a dream. He bent a wire coat hanger into the same shape and “when he revolved it in his hands he found that this crank assembly was different from any other crank assembly ever made. Except for top dead center and bottom dead center, this crank had no dead spots. He was amazed. And in future testing would find that during a rider's maximum effort, power increases at a bikes rear wheel of 20-25% were possible.”

If true, that would be little short of astounding.

Z Torque further claimed “many advantages, including”:

  • Smoother pedaling
  • More power to climb hills
  • Less perceived effort to pedal
  • Faster acceleration
  • Less affected by headwinds
  • Ability to turn higher gearing

However, the Z Torque was really just another crank that connected the bottom bracket axle and pedal by a circuitous route, with an extra problem baked in.

As you can see, the long arm of the V shape, is really, really long. Imagine trying to pedal while banked over hard in a corner and you can probably explain why Z-Torque cranks were never even as popular as PMP Brevettatos.

Our official grumpy Northerner, John has been riding bikes for over 30 years since discovering as an uncoordinated teen that a sport could be fun if it didn't require you to catch a ball or get in the way of a hulking prop forward.

Road touring was followed by mountain biking and a career racing in the mud that was as brief as it was unsuccessful.

Somewhere along the line came the discovery that he could string a few words together, followed by the even more remarkable discovery that people were mug enough to pay for this rather than expecting him to do an honest day's work. He's pretty certain he's worked for even more bike publications than Mat Brett.

The inevitable 30-something MAMIL transition saw him shift to skinny tyres and these days he lives in Cambridge where the lack of hills is more than made up for by the headwinds.

93 comments

Avatar
Mungecrundle [1130 posts] 2 years ago
23 likes

1. Pay attention in physics and avoid getting suckered by perpetual motion machines and other quackery.

2. Never underestimate the psychological power of the placebo effect. Tell enough people enough times in a convincing enough manner that sniffing a rat's testicles before a race will make them faster, and sure enough some will actually go faster.

3. Don't fancy sniffing a rat's testicles? I can supply homeopathic rat bollock odour at just £25 for 10ml, enough for a month's supply.

 

Avatar
ColT [349 posts] 2 years ago
4 likes

Hmm. Magic wristbands, anyone?

 

 

Avatar
hawkinspeter [2663 posts] 2 years ago
0 likes

To be fair, a non-straight crank could possibly be of some use with non-round chainwheels to alter the power transfer, but with a circular chainwheel, there is zero benefit for a non-straight crank.

Avatar
samvegg [24 posts] 2 years ago
2 likes
hawkinspeter wrote:

To be fair, a non-straight crank could possibly be of some use with non-round chainwheels to alter the power transfer, but with a circular chainwheel, there is zero benefit for a non-straight crank.

Still a lot easier to move the chainring rather than the crank arm

Avatar
wycombewheeler [1342 posts] 2 years ago
15 likes
hawkinspeter wrote:

To be fair, a non-straight crank could possibly be of some use with non-round chainwheels to alter the power transfer, but with a circular chainwheel, there is zero benefit for a non-straight crank.

 

just no

 

the relationship between the pedal spindle and the crankshaft is unchanged regardless of the shspe of the metal connecting them.

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brucethebruce [38 posts] 2 years ago
0 likes

I would be wary of these snapping. Did this ever happen ? We're they ever used for long enough in the first place?

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matthewn5 [1232 posts] 2 years ago
0 likes

Anyone ever made a double-jointed crank?

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Eric D [112 posts] 2 years ago
3 likes

"Except for top dead center and bottom dead center, this crank had no dead spots. He was amazed."

True ! LOL

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Grizzerly [369 posts] 2 years ago
2 likes

There's nothing new under the Sun.   This sort of bollocks keeps resurfacing.  Currently it's 'oval' (actually eliptical) chainrings.   The way to eliminate deadspots in pedalling is to improve pedalling technique.   All these gimmicks are just that, gimmicks.   You can't blame the manufacturers for trying to make a few quid,  but simple common sense should tell you that it's a waste of money. 

Avatar
bikebot [2117 posts] 2 years ago
4 likes
hawkinspeter wrote:

To be fair, a non-straight crank could possibly be of some use with non-round chainwheels to alter the power transfer, but with a circular chainwheel, there is zero benefit for a non-straight crank.

Just to check, were you on here a few months ago saying that disc brakes caused bikes to pull to the left, or was that someone else?

Avatar
pakennedy [185 posts] 2 years ago
0 likes

With modern materials (ignoring shape because that's obviously a stupid idea), could you even-out power a noticeable amount utilising a crank? It'd have to flex a touch at maximum potential and return to shape before the effort you put in was negated completely. Obviously, the natural tendency of any such 'power storage' attempt would be to turn it to heat at the storage point.

The things pictured are way too hard to have done that, but I suppose it it plausible to smooth out the power a minute amount. I'm thinking hill climb rather than track obviously where maintaining V is useful.

Avatar
hawkinspeter [2663 posts] 2 years ago
2 likes
wycombewheeler wrote:
hawkinspeter wrote:

To be fair, a non-straight crank could possibly be of some use with non-round chainwheels to alter the power transfer, but with a circular chainwheel, there is zero benefit for a non-straight crank.

 

just no

 

the relationship between the pedal spindle and the crankshaft is unchanged regardless of the shspe of the metal connecting them.

Yes, except for the angle. Imagine that a crank can have a square hole at any orientation (i.e. 90 degrees difference) and thus the orientation of that hole can change the relationship between the pedals and the chainring. With a circular chainring that makes zero difference, but an oval chainring could show a difference in where the peak power is applied. However, a non-straight crank is the most stupid way of changing that orientation (more flex, more weight and less strong) rather than changing how the crank fits onto the crankshaft.

I'm not trying to argue for any benefit with a non-straight crank, but the only possible way that it would physically make any difference would be with a non-circular chainring.

Avatar
hawkinspeter [2663 posts] 2 years ago
0 likes
bikebot wrote:
hawkinspeter wrote:

To be fair, a non-straight crank could possibly be of some use with non-round chainwheels to alter the power transfer, but with a circular chainwheel, there is zero benefit for a non-straight crank.

Just to check, were you on here a few months ago saying that disc brakes caused bikes to pull to the left, or was that someone else?

I'll plead innocent to that. I can't recall ever holding that opinion.

Thinking about it now, that would only make sense if you had really weak/flexible axle otherwise, the forces would be distributed across both sides equally.

Avatar
srchar [1074 posts] 2 years ago
1 like
hawkinspeter wrote:
bikebot wrote:
hawkinspeter wrote:

To be fair, a non-straight crank could possibly be of some use with non-round chainwheels to alter the power transfer, but with a circular chainwheel, there is zero benefit for a non-straight crank.

Just to check, were you on here a few months ago saying that disc brakes caused bikes to pull to the left, or was that someone else?

I'll plead innocent to that. I can't recall ever holding that opinion.

Thinking about it now, that would only make sense if you had really weak/flexible axle otherwise, the forces would be distributed across both sides equally.

This is the first time I've seen someone troll those of us who did A-level Physics. I'll bite. Have another think about how your weak/flexible (totally different properties) axle, contained in a stiff fork and with each end attached to a single wheel rim, could possibly cause a bicycle to pull left when that axle is braked at one end.

Avatar
kwi [293 posts] 2 years ago
2 likes
bikebot wrote:
hawkinspeter wrote:

To be fair, a non-straight crank could possibly be of some use with non-round chainwheels to alter the power transfer, but with a circular chainwheel, there is zero benefit for a non-straight crank.

Just to check, were you on here a few months ago saying that disc brakes caused bikes to pull to the left, or was that someone else?

I remember that thread, stopped commenting when whatever 'flatearther' came out with that as I couldn't be arsed banging my head into my dead horse.

Avatar
spencer-far-i [36 posts] 2 years ago
4 likes
Mungecrundle wrote:

1. Pay attention in physics and avoid getting suckered by perpetual motion machines and other quackery.

2. Never underestimate the psychological power of the placebo effect. Tell enough people enough times in a convincing enough manner that sniffing a rat's testicles before a race will make them faster, and sure enough some will actually go faster.

3. Don't fancy sniffing a rat's testicles? I can supply homeopathic rat bollock odour at just £25 for 10ml, enough for a month's supply.

 

 

Do you accept Paypal? 

Avatar
P3t3 [429 posts] 2 years ago
1 like

[/quote]

This is the first time I've seen someone troll those of us who did A-level Physics. I'll bite. Have another think about how your weak/flexible (totally different properties) axle, contained in a stiff fork and with each end attached to a single wheel rim, could possibly cause a bicycle to pull left when that axle is braked at one end.

[/quote]

Surely you can twist the fork legs under heavy braking due to the caliper only being on one leg.

I had a road bike where the fork legs were twisted and it gave the bike a tendency to steer one way so i had to hang a long way off one side to ride no handed.

Can't see how you'd affect the axle mind.

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WashoutWheeler [114 posts] 2 years ago
0 likes

Last few remaining 100grm packs of Magic Beans guarenteed to give you Froome like performance, for life! Only bids over £25,0000. per pack considered.

Avatar
hawkinspeter [2663 posts] 2 years ago
1 like
srchar wrote:

This is the first time I've seen someone troll those of us who did A-level Physics. I'll bite. Have another think about how your weak/flexible (totally different properties) axle, contained in a stiff fork and with each end attached to a single wheel rim, could possibly cause a bicycle to pull left when that axle is braked at one end.

You're right - the axle shouldn't make any difference. I'll admit to having a few beers before posting that. Maybe in theory a weak flexible hub could deform with disc brakes but you wouldn't be riding with a wheel that behaved like that.

Avatar
bikebot [2117 posts] 2 years ago
1 like
hawkinspeter wrote:
bikebot wrote:
hawkinspeter wrote:

To be fair, a non-straight crank could possibly be of some use with non-round chainwheels to alter the power transfer, but with a circular chainwheel, there is zero benefit for a non-straight crank.

Just to check, were you on here a few months ago saying that disc brakes caused bikes to pull to the left, or was that someone else?

I'll plead innocent to that. I can't recall ever holding that opinion.

Thinking about it now, that would only make sense if you had really weak/flexible axle otherwise, the forces would be distributed across both sides equally.

Also why the bottom bracket and crank must have as little flex as possible, the bike might dangerously pull to the right when sprinting.

Avatar
hawkinspeter [2663 posts] 2 years ago
0 likes
bikebot wrote:

Also why the bottom bracket and crank must have as little flex as possible, the bike might dangerously pull to the right when sprinting.

I can't even imagine how Christian Haettich counters that. http://www.bbc.co.uk/news/magazine-30295759

Avatar
dave_t [22 posts] 2 years ago
6 likes
bikebot wrote:
hawkinspeter wrote:

To be fair, a non-straight crank could possibly be of some use with non-round chainwheels to alter the power transfer, but with a circular chainwheel, there is zero benefit for a non-straight crank.

Just to check, were you on here a few months ago saying that disc brakes caused bikes to pull to the left, or was that someone else?

That depends on which hemi-sphere you're in .... pulls to left in the north, to the right in the south. I have this on good authority.

Avatar
mike the bike [1119 posts] 2 years ago
1 like

 

Even the 'experts' can be fooled.  I remember years ago reading a review of a disc-braked motorcycle in which it was stated that, as the brake calliper was behind the fork leg, the front of the bike would lift under braking.  This from a professional magazine writer.

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mylesrants [423 posts] 2 years ago
0 likes

i love them. Hope they make a handlebar stem to match

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therevokid [1023 posts] 2 years ago
0 likes

is my calendar wrong ?? ...  3

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horizontal dropout [301 posts] 2 years ago
0 likes

1) Apostrophe alert: "It’s unusual (but, as we’ll see, by no means unique) feature..."

2) There's more spring in a longer lever (other things being equal) so you would store energy during the down stroke and release it as your foot pressure reduces. Some would get converted to heat but some would be returned. So it could theoretically smooth your pedalling.

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gnarlyrider [32 posts] 2 years ago
1 like

...seeking crowdfunding for centrally mounted disc brakes..should fix pulling to left or right .. just need to to get the brake mechanism to move in and out to avoid the spokes.  

or wait for the mark II product: double disc brakes one each side with independent actuators - can steer left or right just by braking.  

Should be able to sell loads of these in a groupset including cranks made of cheese to reduce peak loads on your knees.

Avatar
bikebot [2117 posts] 2 years ago
2 likes
Quote:

There's more spring in a longer lever (other things being equal) so you would store energy during the down stroke and release it as your foot pressure reduces. Some would get converted to heat but some would be returned. So it could theoretically smooth your pedalling.

This does make me  wonder why no manufacturer ever tried an elastomer crankset. It looks like they would have found a few customers.

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Bmblbzzz [231 posts] 2 years ago
4 likes

Interesting that CW's "Surrey roadman" said back in 1981 they seemed to smoothe out his pedalling but only at lower cadences. Could it be that knowing he had these weird cranks made him, consciously or unconsciously, pay more attention to smooth pedalling technique, and that this went out the window at higher cadences? So there might have been a real effect, but it was psychological. 

Avatar
bikebot [2117 posts] 2 years ago
2 likes
Bmblbzzz wrote:

So there might have been a real effect, but it was psychological. 

Basically, the latter.  As JS summarises in the article, it's entirely bollocks.  The same kind of bollocks gullible audiophiles used to fall for in droves back in the 80's and 90's.

The Cycling Weekly tester was writing shit worthy of this -> http://wathifi.com/

And for anyone still not sure, I've got some speaker cable I'd like to sell you.

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