I was thiniing of how i could Re-enforce my new seatpost once it gets here and i came up with this… It would probably only work for 22.2mm Seatposts but i think it would make them alot stronger.
What you do is take a second seatpost thats 2 sizes larger than the one in question(If you had 22.2mm then get 27.2) so that yours will fit snuggly inside the other. Then you cut the new one to fill the space between your frame and saddle and slide that peice onto your seatpost. This will essentially double the thickness of your seatpost and(in theory) make it stronger and less susceptable to bending.
The only real disadvantage to this that i can see is the added weight from the second piece of seatpost that youre adding.
So, experts. Do you think it would work…Is there any suggestion that would make it work better. What other disadvantages could you see with this plan?
You can’t adjust the height of your seat. And it would most likely break right at the point where it fits into your frame, which is where the outer post ends. Maybe you could add some kind of material to the inside of the 22.2 post to make it stronger, but I kindof doubt it. Something to think about.
Well i dont kno about you but i dont have 20 different sized people unsing my uni so my seat hieght never changes.
And because of the over lap that the second peice of seatpost would have on the seatpost clamp it would be very unlikely that it would be able to tip enough to break… However after i try this i will let you all kno how it works.
why not do the same thing but instead put a section of 22mm seatpost inside a 27 mm seatpost?
I still dont think its a very good idea because although it would make the tube stronger it would just move the stress up to where the post connects to the plate.
I’ve seen a few post failures and they all seem to be connected to failure of the mounting plate at the top of the post, rather than the post itself, maybe the post itself isn’t the thing to concentrate on improving.
Your design is likely to concentrate the stress at the point where the outer tubing stops, and will likely cause snapping of the inner post just above the top of your frame. However, some interesting ideas stem from yours, namely a seatpost that changes diametre, thin at one end to fit in the frame, with a larger diametre but equal metal cross-section at the other (i.e. thinner walls). This would weigh no more but the increased diametre increases the second moment of inertia and thus increases the beam yield force. But then i suppose if you’re going to all the trouble of that you may aswell just use a frame with a bigger seatpost tube and use a large, thin wall tube.
You could try welding a flat flange down the front of the post, this would make the post vastly more difficult to bend, it would certainly move the failure point up to the seat mounting plate.
Random thought: why do we use circular posts to mount seats on? Bearing in mind that the seat doesnt need to rotate, and the vast majority of the force are front/back rather than left/right wouldn’t an I-beam or similar be better? It’s far too tedious for me to work out right now, does anyone know off-hand for an equal material cross-section (or mass per length) whether tube or I-beam is stronger?
isn’t a hollow cylinder the best weight-strength or thickness/strength ratio… so that said the I beam would be weaker… but it is a good idea
umm they could be made slightly oval or square or something too, im probably not right tho cuz I didn’t research it out or anything
hm… rectangular seatposts for christ?? whos starting that one?
I think an I-Beam seat post would likely fail becuse of torque. I mean with a standard seat post it if’s just a little bit loose, it often gets turned a little bit whole riding, which certainly indicted that some torqe forces are applied to the post during riding especailly in turning.
the problem with seat posts is the way they are made.
as welding is very weak and it can be subject to a lot of stress and therefore end up breaking.
the manufacturers need to start making them by casting. this is not very possible unless you have a workshop but even then it is not easy. if you were to make a one off, it can be done by sand casting.
therefore it is unlikely that many of you will be able to do it at home.
this way of making the seatpost would take much longer so it would be much more expensive but also a lot stronger if done properly, as there is no welding that is needed to be done.
so if any of you own a unicycle making factory or work in one you could suggest this idea
I actually have my seatpost reinforced right now, I guess this would work for pretty much anyone, and it’s really simple to do too.
I had a lot of problems with the little tab on top of the seatpost bending, when I landed on the front bit of my seat. The tab would bend down, and the seatpost would be ruined. So I came up with this clever idea, to weld a little piece of metal in between the tab and the seatpost. This will also stop any breakage due to pulling hard on the seat or anything, and will also stop ripping of the area between the tab and the seatpost.
Unfortunatly, the unicyclist.com gallery is not exactly cooperating, so the illustration will have to wait for a bit.
Erant has invented the gusset. Just as I did in the early 90s. The engineering concept behind it is quite old, but it seems the simplest way to keep your seatpost from breaking. I have many different seatposts that have been reinforced in that manner.
Is anyone out there having problems with seat posts that don’t involve the plate where it connects to the seat? That’s the part that needs reinforcing, the tube is usually fine. Today’s stronger, stiffer seats, and the type of riding we do now with lots of seat yanking, both are causes of more seatpost problems than in the past.
It is, I’ve thought up quite a few different things, but this was the only that thing that was easy to fabricate, and easy to install. That is, for anyone that has access to a MIG welder. I originally intended to build one that is removable, just in case I do break a seatpost, but never needed it. Been riding on this reinforced seatpost for about 6 months now, no breakage.
