[juanbeegas]

Would this work, or is it a catastrophic failure in the making?

 

[23mjm]

Danger Will Robinson Danger Will Robinson.

I hope your joking---what are you going to save 15 gram on the spindle, and 50 grams after they have to remove your ball because you smashed them on the top tube when your spindle broke!!!!

 

[savagemann]

Oh wow.........I sense it may not go too well.

 

[juanbeegas]

Any explanations why it would fail? I never thought of doing it until a friend mentioned it. Downward forces that would crack the spindle are not focused on the centre of the spindle, where the drilling would be... I'm just interested in a proper explanation of why it would not work.

 

[AZ]

Any explanations why it would fail? I never thought of doing it until a friend mentioned it. Downward forces that would crack the spindle are not focused on the centre of the spindle, where the drilling would be... I'm just interested in a proper explanation of why it would not work.

The forces ARE concentrated in the middle of the spindle . The forces are also twisting forces not downward directional forces . It would be much easier and productive to save rotating weight in wheels . :thumbsup:

 

[SteveUK]

EDIT: pardon for the repetition, AZ; we were typing at the same time.

Downward forces that would crack the spindle are not focused on the centre of the spindle, where the drilling would be.

Would there not be a high twisting force on the axle? For example, while you're stood on the pedals, with the cranks level, both feet are pushing down, it is the strength of the axle that stops it just twisting itself in two. I would imagine that there's a fairly high load through the center, and an axle which was weakened there would just tear itself apart.

If you imagine the axle being made of, say, soft clay, then imagine what would happen if both pedals were pushed down-over at the same time; it's going to twist quite neatly in the middle. That's how I see a weakened axle failing.

That's intuitive rather than (particularly) informed, so I'm afraid you're still going to have to wait for somebody with numbers and stuff to say for sure one way or the other.

 

[spartan034]

Even IF AND ONLY IF this actually didn't result in failure, it wouldn't be worth the 15 grams you would save.

that is like taking 15 paper clips out of your pocket. Is this going to make you ride faster? No. its not.

If you want to drop weight at the cranks, post in the weight weenie forums, With the right combination and depending on what you're running now you can make make some real improvements.

Yes, the center of the spindle is not under much stress from the net downforce of your pedal strokes or your weight, but it is under a lot of load when you stand up and under a massive load when you land a drop standing. :nono:
The spindle is being "twisted" in these conditions.

This is almost as bad as drilling holes in your frame to save weight.

I think of stuff like this as: "If it is a good idea, the manufacturer would already be doing to to some part"

Notice no cranks come with holes in the spindle. :madman:

 

[juanbeegas]

Thanks, those were the kind of responses I was looking for.

If you imagine the axle being made of, say, soft clay, then imagine what would happen if both pedals were pushed down-over at the same time; it's going to twist quite neatly in the middle. That's how I see a weaked axle failing.

I especially liked this for putting it in a way a regular dude with not much mechanical knowledge could understand.
Thanks again.

 

[LarryFahn]

DO IT! Post vids too.

 

[Drakken_11]

I agree, the amount of weight resulting from the small holes is so negligible that you won't even notice it. I totally understand your thinking behind it. I used to go Rock Climbing and we would cut the handle of a tooth brush (for cleaning out hand holds) off to save weight.
As far as safety...... I'm not sure. Do manufactures put those things under stress tests???

 

[ziscwg]

just replace all your bolts with Ti bolts..................
It will be cheaper than that ER visit you are probably going to need.

Just look at it this way, with all the marketing about weight for bike stuff, dont you think some engineer thought of this already to save weight? There must have been a good reason not to go with it.

 

[Drakken_11]

Hey, Ziscwg. By Ti do you mean Titanium??? Where can you get them?? Do they make bolts and things out of 7075 Aluminum. And would they be lighter?? Or would it just strip when you try to tighten it??

I'm sure that if he is to the point of drilling holes in the BB; he has probably already gotten the lightest stuff he can on his bike.

I too would love to see a Video of this. 1st of the proccess and 2nd of the Maiden Voyage. Hey, he could win some $$$ on Americas Funniest Videos.

 

[juanbeegas]

Nah, not actually doing it. It was just a little discussion a friend and I got into late one night over a couple drinks.


Drakken 11 - Fleabay is your best bet for titanium bolts. I got all my bolts there. You just have to know the sizes you're looking for. Currently running ti bolts on my rotors, my brake calipers, brake adapters, shifter bolts, brake levers and the pinch bolts on my cranks. The stem's the only place I'm a little hesitant to install them on.

 

[Drakken_11]

Cool thanks, I'll check it out. Are they really that much lighter??

 

[civil]

Where can you get them?? Do they make bolts and things out of 7075 Aluminum. And would they be lighter??

torontocycles.com

Yes, they also have aluminum bolts.

Ti bolts are ~ 1/2 the weight of steel, Al bolts are ~ 1/3 the weight.

Not a good $/gram ratio though unless you have already weight weenied you're bike and are looking to save a few more grams.

An example would be changing rotor bolts to Ti. Approx. 12g savings for 50 to 60$

 

[Drakken_11]

Thanks I'll give it a look. But I think that may be alittle hard on the pocket right now.

 

[selector]

I think of stuff like this as: "If it is a good idea, the manufacturer would already be doing to to some part"

That there sums it up. Weight is important; it all adds up. But, structural integrity means something too.

 

[juanbeegas]

Thanks I'll give it a look. But I think that may be a little hard on the pocket right now.

Dude... Check out Ebay, it's a lot cheaper than you think... For example, Enough ti bolts for both XT brake calipers cost me USD$11(4 x M6X18.5mm).

PM me if you want the dude I buy from.

 

[Drakken_11]

Yeah man, that's more like it. Do you think they would have some like the ones that hold the Disc on?? I need to lighten the front end on my Hardtail.

 

[Killroy]

Take it form a WW that has "tuned" parts before, you will never remove as much weight as you wish.

From a stress perspective, it would be better to thin the wall thickness.

Speed/ Weight holes are always stress concentrations and you will see it on Finite Element Analysis.

Other suggestions like swapping for lighter parts is a better move. Low hanging fruit for weight reduction: Light tires, tubeless tire sealants, 1X9, foam grips, trim extra head tube and trim seat posts