Double Isis Cranks

[sayshell]

So here is my idea I think it would result in the strongest cranks ever that last 200 years. What you do is you make the isis mount hole on the crankarm a couple mm bigger than a normal one. Than you put a steel isis shaped star which reduces it to the size of a normal isis spindle. The star would fit into the crankarm directionally with one end having a cap so it can only move one way and the crankarm bolt would stop it from moving the other. The star would be a precise fit that takes an extreme amount of force to hammer in.

This would result in immortal cranks I think with almost no weight penalty. Why is this better? simple The connection between the aluminum crank and insert would now be ridiculously tight and hammered in with a billion pounds of force so the aluminum/steel contact point would not warp or develop play, and the crankarm fit with the steel/isis spindle connection would be loose enough that you could still remove the crankarm. This would also spread the stress out better on the crank making it less likely to snap or crack near the spindle connection which is where cranks seem to always break because the aluminum portion of the connection point is a much larger area thus distributing stress out more evenly.

To make this crank would also be super easy with all the cnc machining these days so it would sell for cheap.

Can anyone find a loophole in my idea? I thought it though a fair bit and can't find a flaw.

Edited June 18, 2009 by sayshell

[James Quigley]

I've never seen cranks snap at the bb/isis mounting end. Always halfway up or nearer the pedal.

Also why? my try-all cranks are a good 3 years old and havn't got any play, all threads are fine and the hole for the isis has no play at all.

I render your idea null and void.

[sayshell]

I've never seen cranks snap at the bb/isis mounting end. Always halfway up or nearer the pedal.

Also why? my try-all cranks are a good 3 years old and havn't got any play, all threads are fine and the hole for the isis has no play at all.

I render your idea null and void.

for people who are hacks and heavy. You are probably a very smooth rider.

[forteh]

for people who are hacks and heavy. You are probably a very smooth rider.

A steel insert wont increase the strength of the cranks at all, all it may do is reduce the wear on the isis spine in the crank, but then the steel insert will come loose effectively wrecking the cranks

If you want stronger cranks use a stronger material.

[stunt man t]

I've never seen cranks snap at the bb/isis mounting end.

they were 2 months old

Edited June 18, 2009 by stunt man t

[forteh]

they were 2 months old

Thay havent failed because of the ISIS spline though

[eskimo]

A steel insert wont increase the strength of the cranks at all, all it may do is reduce the wear on the isis spine in the crank, but then the steel insert will come loose effectively wrecking the cranks

If you want stronger cranks use a stronger material.

My thoughts exactly. The ISIS join will only wear if it works loose, use some thread lock on the crank bolt and it should be all okay. As above in bold, and/or more material.

[edit]

But it's definitely good people are thinking.

Edited June 18, 2009 by eskimo

[tris]

Good idea but it's kind of already been done with Odyssey Wombolts surely?? They usilise a wedge cluster using the smae methed to create and untra tight fit........

BMX cranks and bearings should be used on trials bikes, its seems on sensible, trials BB's are bolocks as are their cranks (square tpaer anyway) . If i was to get another 24" i'd 'BMX parts it up'

[eskimo]

Good idea but it's kind of already been done with Odyssey Wombolts surely?? They usilise a wedge cluster using the smae methed to create and untra tight fit.......

BMX cranks and bearings should be used on trials bikes, its seems on sensible, trials BB's are bolocks as are their cranks (square tpaer anyway) . If i was to get another 24" i'd 'BMX parts it up'

I think the reason is because alloy frames and press fit bearings might cause some problems. Seeing as it's a high stress area. The problem with mtb shells is just everything needs to be crammed into such a small area, or at least that's how i see it. Though most don't have any problems and seeing as trials is concentrated more on weight that strength...

[Revolver]

Two things, I think could be made to improve the choice of cranks:

A triangle taper, because wear on that would be less apparent, and separate ISIS axles that would fit external BBs, so you could use an external BB with ISIS cranks.

[Greetings]

While we're talking about improving cranks, my suggestion is HG/Spindle splined cranks. Stop with the screw-on nonsense, it makes life miserable.

I discussed this with Deng but he says there needs to be full backing from all the manufacturers to introduce such a solution.

[Luke Rainbird]

Thought that up a fair while ago - it'd make life so much easier!

Obviously you lose freewheel compatability unless someone makes modified freewheels too, but whoever decided that threading on a highly torqued component was a good idea was a goon

[forteh]

While we're talking about improving cranks, my suggestion is HG/Spindle splined cranks. Stop with the screw-on nonsense, it makes life miserable.

I discussed this with Deng but he says there needs to be full backing from all the manufacturers to introduce such a solution.

Surely its the same with his free hubs, dont they all use a non-standard spline interface?

I know if trialtech (for example) machined an HG spline onto their cranks instead of the thread then people would use them. Would need to use very wide based sprockets but that isnt a massive issue

[eskimo]

Two things, I think could be made to improve the choice of cranks:

A triangle taper, because wear on that would be less apparent, and separate ISIS axles that would fit external BBs, so you could use an external BB with ISIS cranks.

I think the reason they don't do that is because the material will be thinner at the points of the triangle on the crank.

While we're talking about improving cranks, my suggestion is HG/Spindle splined cranks. Stop with the screw-on nonsense, it makes life miserable.

I discussed this with Deng but he says there needs to be full backing from all the manufacturers to introduce such a solution.

Too right. Even if it wasn't Shimano compatible like Echo's hubs, least we can still swap and change without a headache.

[Dan6061]

Fixing something that isn't broke, I think. Can't say I've ever had this problem with ISIS cranks. My Tensiles are such a tight fit on the axle anyway, it takes brute force to get them off without the correct tool!

Just make sure the bolts are tight all the time too, and you won't come across any problems with it.

[kyle-livesey]

dont think they make hammer with a billion pounds worth of force

[Mark W]

If you have to hammer anything on with a shitload of force, I'd say that was taking a massive step backwards no matter what you're doing. Similarly, if you've got to hammer the shit out of them to get them on the spindle, a lot of that force is going to be going straight into your BB bearings in the form of side-load, which they're not really made for. (EDIT: Think you might've meant the insert needed to be pressed in, then you just put them on like normal cranks? I don't really get the point in that - if you keep your cranks tight and don't take them on and off all the time most ISIS cranks tend to hold their shape alright. It's also pretty much moving the problem from one point slightly further out to another? It's always the soft alu crank arm that gets deformed, not the steel spindle, so if you're just basically bulking out the spindle itself by adding another piece of steel to it, you're just making the alu/steel interface get moved out slightly?)

Regarding doing triangular spindles - if you think about it, you're asking the tips of those triangles to resist a lot of force. The ends of the splines are what stops your crank just spinning around the spindle, so if you reduce the number of them you're ramping up the load they have to take. It's basically the force you put through them divided by 3, whereas with a splined setup now it's 6 (or 8 or whatever it is). It's all a balancing act.

[cai]

I don't really get the point in that - if you keep your cranks tight and don't take them on and off all the time most ISIS cranks tend to hold their shape alright.

Maybe this steel insert is not the correct solution - but there is definatly a problem their, look at the amount of people who have had to resort to using the coke can bodge to stop their crank wobble. Plus I'd like to be able to remove the cranks without the thought of "this is ruining the splines on my crank arm", what with the amount of freewheels people go through cranks tend to be taken off every so often.

[JonMack]

What, so the manufacturers should think up a whole new system because people are unable to keep their bolts tight? That's why cranks round off, because the BB bolt is loose, hardly a reason to start an entire new crank design. Also, you're not going to ruin your cranks by taking them off, I always make sure my BB and cranks are nicely greased to make it easy to remove them should I have to at any time.

Anyway the majority of manufacturers are now onto external bearing BB's, but as per usual trials is years behind.

[Mark W]

Maybe this steel insert is not the correct solution - but there is definatly a problem their, look at the amount of people who have had to resort to using the coke can bodge to stop their crank wobble.

I've heard about people using coke can bodges for square taper, but hardly any using it for ISIS cranks?

[Tomm]

Can anyone find a loophole in my idea? I thought it though a fair bit and can't find a flaw.

You're introducing an extra interface. That's just asking for even more wear, and since either interface can fail, you're doubling the risk of rounding something off?

Anyway the majority of manufacturers are now onto external bearing BB's, but as per usual trials is years behind.

I was thinking about this though, trials was way ahead with all the fluoro shite. That's only just hitting MTBs now really, and fluoro rims have been out on trials bike for ages. 2 years or more? Not that that's anything to be proud of

[sayshell]

people are ignoring the point. Ok i will explain this better. The alumium portion of the crank would be basically integrated with the steel portion as opposed to the aluminum portion being a relatively snug fit on the steel portion. You would never have to remove the steel insert from the crank and the pressed fit would spread stress out as evenly as possible as opposed to a fit like on a normal bottom bracket in which it is nessacary to remove the crankarm and install it. The steel insert would never warp because steel is really tough, and the alumium/steel contact point would never warp because it has a larger area of contact and is a perfect fit. The point is tight fits are much stronger than loose fits and you can not have a EXTREMELY tight fit on a regular crankarm because it would be impossible to install onto a bottom bracket or remove.