sorry guys, gotta go to a wake in a sec, anyway
I might add a suspension seatpost also, if i have space, i have my own ideas for an inexpensive one lol. At the moment my feat is to make the unicycle as i plan it
I have discovered the limits of the “elastic properties” of standard cranks. The type of metal, thickness, and degree of temper could be varied. (define large drop)
not to be a buzz kill but unless you have a couple years of machining, welding, and fabricating experience which i highly doubt you do this will be damn near impossible. its one thing to make a doodle of it. do you have any technical drawings of it? dimensions? do you know what your going to make it out of? who is going to do the machining? and what are they going to use to make the parts?
this project will take money and lots of it. 50$ and a spare uni frame isnt gunna cut it. also this isnt a weekend (yay lets build something) kinda thing this is more like a senior thesis.
the idea is very good, but i doubt you will make any process on it, and you will soon realize this. hopefully someone with more skills and deeper pockets could bring this to life. this design has hope
someone needs to CAD this up, we can then go from there.
double post
Even if it doesn’t work, think of all the machining, welding, and fabricating experience he’ll get while working on it.
He also may surprise you.
unibikeling, you should check Hugos post in your other thread. His design is brilliantly simple and if you had the arms that make the triangle pivot at the center points of the gears (eg. directly behind the cranks and on the wheel axle) you would not have any changes in chain tension and also you would not have any rotation of the cranks or the pedals with the compression of the suspension.
His design fixes the two biggest problems with yours and does not require much for extra parts. I urge you to consider his design as the vertical chain and dynamic tensioner that you have now will only cause you headaches.
Designing machines and processes is definitely a cool way to spend time because there are so many tangents that lead to other things… But sometimes simple is better. The Harper’s idea to spring the cranks is beautiful in it’s simplicity. If a full sized car can have torsion suspension it isn’t out of the question to come up with a system that could survive. If the system does get overloaded and deformed, it would suck a lot less than getting compression fractures. They hurt… They hurt pretty bad.
^^^ is the inspiration i need. Captain Buzz Kill, i seriously think i can go against all of your logic and create this. You think im seriously machining things? i can get all this done with a plasma torch, wirefeed welder, some bike parts, and my old uni. Ive thought it over and over, and ive replaced things with other things, then taken them back down to reduce weight. Considerrably, $50 is what i need, all i need are a few berrings and housings for them, all other metal i can get from around my house. Another thing too, i dont have too much expertice, but my dad does. Same with my brother, and the community of unicyclist.com. I believe i can do this.
Also:
Thats a splendid idea, brilliant. I might give that one a try also, i may just take like a small wheel, or something, and create a small one, just to see how it works. (i probably wont though) but grats on the design. My design on the other hand, i think, would allow more travel on the tire, possibly not.
Edit: for my design, i want the cranks and pedals to stay relatively in the center, and im not going for any muni or trials at the moment, possibly later if i like build it like a tank, but not its just like to see what it does, explore its depths, and see what happens on road riding, see how smooth i can make it.
so, best of luck to anyone else trying to win the space race of suspension!
p.s. c9ollie, its not a doodle, it’s a planned out sketch, that took hours of thinking, a doodle would look like -
Regarding the flexible crank arms; might you be able to implement that just by making cranks out of titanium? Titanium’s ductility would provide the spring, and the cranks could still be made pretty strong.
and also great idea on the flexi cranks, could solve a lot
With no sarcasm, i have to say, that’s a really impressive idea. I can’t say I like your “technical drawings”, but whatever. Mine weren’t any better at 14.
A couple of details: I don’t think this design saves anything from Harper’s idea of sprung cranks. You will still feel squishiness when pedaling hard from the suspension compressing as well as the tensioner springing itself.
While I would love to see this design succeed, and love to see your prototype, I honestly don’t believe this can be done with just a plasma torch.
I’ve worked in metal shops ranging from architectural/high-end sculpture shops to precision cnc and manual machine shops for 4 years now (I started at about your level). I would give myself $300 minimum, about 30-40 hours of work, and expect a mediocre prototype as a result. Mind you this assumes I have full access to my machine shop and the shop I work at, including over $750,000 worth of torch welders, forges, plasma cutters, cnc waterjet machines, cnc turning centers, cnc mills, manual mills, drill-presses, manual mills, and support equipment.
That said, when someone really wants to get something done, who’s to say no? As Mike said, you’ll learn a lot from this.
Since you’re 14, I will assume you have yet to take a calculus course, machine design class, or engineering statics or dynamics class. Here’s a couple of details you’ll notice if you take a set of plans for this to an engineer (which I am not, mind you):
-The suspension will compress more easily than it will rebound, inherently to the design. This is because the tensioners will have an easier time pushing out than being pushed back in. Think about simple vector addition if you don’t understand why.
-You may want tensioners that tension both sides of the chain, rather than one. That way you won’t find that one direction of pedaling has a “squishier” feel than the other.
-There is no way to eliminate the squishiness of pedaling from this or any other suspension design. If you increase the strength of the tensioners, they will simply pull harder on the vertical pistons, which will compress more easily and reduce responsiveness.
This is an interesting dynamics problem. The length of your chain is not a trivial question. The straighter it is (less tensioner pushing out), the bigger the damping of the piston will be on rebound, and the less the tensioner will be able to keep the chain tight. On the other hand, if the tensioner sticks too far out, it will be unable to pull all slack from the chain when the suspension is at long travels.
I recommend you draw this up in Solidworks or the like. A rough sketch like this is very, very far from a buildable model as it is, and you will save yourself a lot of frustration if you iron out the details before you start to cut metal.
Good luck, and keep up these ideas. Even if you can’t make them work, this is how you’ll become a great mechanical engineer.If anyone is really interested in making a set of suspension cranks, I could see myself making a set next summer… I’ve been looking for a good machining project related to unicycling.
(I know the parties on campus are lame tonight when I find myself at my computer here… Whatever, the night is young)
Thanks for your comments :), ive had a few designs, i actually have a drawing of dimensions that im not going to release until further notice. The chain tensioners ARE on BOTH sides, i just had a drawing of one side, just to show an idea. That sketch has also undergone a bunch of changes. People have been telling me relatively the same things. The shocks wont give enough action/reaction to anything it does, so i’m replacing them with springed pistons, (a spring inside a piston), none of this really need machining, i have access to a machine shops, but all i need that for is the axel. Also, the springs im using arent going to be anything light, i’m going to make them as tough as i can, i’m going to make a few different types of them with different springs, test them each out, and then choose one. I plan to put about 30 hours into building this thing, no doubt. But, for now its a prototype. My first uni is going to just be big, clunky, and heavy. Then im going to figure out what i can do. My dimensions are huge to fit everything. I’m hoping to slim the uni down to almost the normal size of a uni. Thanks for your feedback though
-Graham
Unibikeling, There’s no reason why you shouldn’t go ahead and work on your design… Maybe it won’t go the way you intend, but you never know what it may lead to unless you try. There has to be a butt load of great inventions out there that started out as one thing and then evolved on there own into something else, not to mention the great practice you’ll get stretching your skills during the build. Look at Sunfish Sailboats… A huge thing that started out in a garage, or Burton Snowboards, or any number of other impressive companies and designs that came about from a person or persons with an idea and the fortitude to keep going when things were rough. Keep on keeping on troop!
Thankyou, its nice to have a supporter, and mabye you should hop into the space race of suspension unicycles, create your own plans. Theres for sure more than 3 ways to give suspension. (squish pedals, float frame(my design), and the one that makes more sense, hugo’s design of course lol)
-Graham
Hey guy, I know from experience what it’s like to push ahead even though people say stuff won’t work. I came up with a way to reproduce complex wooden bows quickly and precisely in a way that mimics a CNC machine but is driven by hand. If you want to see one of them, google paddle bows and then go to my eBay store. Anyway, You may become one of the next great frame builders so I’d hate to see you give up. Working on a way to suspend a unicycle will give you a lot of quality hands on experience which would make building a frame jig and fabricating conventional frames pretty straight forward. Titanium frames, crazy cool alloys like the new liquid metals, the only thing stopping you would be you. With everything being made in China now days, there’s always room for hand crafted high quality products. Think of your idea to suspend unis as a beginning of Unibikeling, Inc. not as a final goal. Who knows, if suspensions are your passion, your efforts may cross over to Karts, motorcycles, Airplane landing gear suspensions, or any number of other avenues. When people say you will fail, it’s something that should motivate you to work harder.
has anyone thought about using hydraulics? it wouldnt work quite like suspension. but you could just drop the frame so it’s right on your tire when you park it. actually you probably use something like the set up in an office chair. you just wouldnt be able to raise it while you were rollin. I know a guy in edmonton here who builds billet wheels and he figures he could build something to work with a uni hub. then just do a lil gold flake chameleon paint job on there. big pimpin ladies. big pimpin 
Your talking about a tire with hydraulic pistons in it? well, if you are, tjpse sytems dont work unless your able to mount a piston in one area, and not have it move, which would sorta defeat and abilites, if your talking in the frame, its not actuall suspension
I’m talkin about having the “pistons” in the frame. So that it would raise the frame to a comfortable length for cruising but u could lower it just for fun. Obviously I’m not talking about using it for its suspension qualities. Id love to just roll up to the store on my uni and lower the hell out of it, then you ride it real nice and slow. That would be badass. As for the rim. I was just sayin that cause if you could get a one off billet wheel for your flaked out slammmed down street uni. Well that would be a beautiful thing to me.
sounds cool. Draw up some plans man lol. instead of the frame, why dont you jsut do seatpost? because the frame would end up sitting on the tire lol. A seatpost with a deskchair hydraulic in it would be pretty cool
the seat post would be easier. this is true. but im thinkin of it more from a “car guy” sorta view. and the idea with that is to have the frame sitting on the tire for show when its parked. with as little clearance between the frame and the tiree as possible. but its just a loosely concieved idea. a vision.