I have to get a new guide rod (i.e., the solid cylindrical steel piece that holds the upper guides) for my 14" HF BS.
The O.D. of the rod is the same as 1/2" pipe: can I cut a piece of that, or are the forces enough that it requires solid rod?
Thanks, H, certified backyard engineer
It will withstand the forces.
UA100
Actually come to think of it a pipe *might* be better. Usually tubing is stronger than rods. That's why bicycles are made of tubing...partly because it makes the bike lighter, but also because it's stronger. Klein and Cannondale use fat, yet light aluminum tubing in their bikes to counter the weaker nature of aluminum as compared with steel. They can make a bike that's lighter than steel yet is stiffer.
The only problem I see is the locking bolt might leave marks or deform the tubing's softer metal. But it should be able to handle any normal stress put on it.
Layne
Are you sure that tubing is stronger than rod? I can believe this is true when scaled by weight or mass but it doesn't seem to me that it would be true when the tubing (O.D.) and the rod are the same size.
For example: Tubing with an O.D of 1 1/16 inch and an I.D. of 15/16 inch (i.e. 1/8 inch wall thickness) would have the same cross-sectional area of material as a solid 1/2 O.D. inch rod. The weight of each of these would be the same (per unit length, and made of the same material) and I believe that the tubing would be stronger (more resistant to bending). However, I would think that a solid rod of the same 1 1/16 O.D. would be stronger than the tubing (of course the rod would weigh more).
Another way to look at the situation is the following: Consider a tubing of a certain O.D.. If you start with a very thin wall, it won't be very strong, but as you thicken the wall it will get stronger and stronger. At some point you will have filled in the tubing, giving you a solid rod. At what point would you have the maximum strength? I would think it is at the limit of the rod.
Again, if you consider the strength per weight (or mass) I can see that there could be an optimum wall thickness for the tubing. In this case you have the trade off of increasing strength and increasing weight as you increase wall thickness so the ratio of these two increasing values could be maximized at some intermediate value of wall thickness.
Granted, I'm not an engineer so I may be missing something but I think the statement that tubing is stronger than rod assumes the same amount of material, not the same size O.D. To put it another way, if you only had a certain amout of material you would be better off making tubing than rod for maximum strength.
BadgerDog
Tubing is weaker than rods of the same diameter. The trick is that most of the strength is in the outer portion, so you don't lose much when you make it hollow.
You would barely be able to lift a bike made out of 1" steel rod.
GTO(John)
Same material, same diameter, rod is stronger.
Sorta kinda. Pound for pound tubing is stronger than rod in bending and compression as long as the wall thickness is great enough to prevent buckling. In tension the strength is the same for both. Diameter for diameter rod will be stronger but heavier.
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