Cool project. What’s the effective wheel size you’re shooting for with
this thing?
Chris
harper wrote:
> I have assembled the first of the two planetary geared hubs. It weighs > in at 1.67 kg or 3.67 lbs. It is one stiff mechanism. I ran it in on a > lathe to warm it up at some high rpm (well, not high for a stud like > me…only about 1000 rpm) and after that it ran a little more > smoothly. I can’t feel any backlash but I will have to get a crank and > a wheel on it to measure that with any accuracy. Now it’s off to the > wheel builder and then onto the frame. Pictures will come later when I > build the second one because it won’t be filled with grease. > > > > > – > harper > Posted via the Unicyclist Community - http://unicyclist.com/forums
I have assembled the first of the two planetary geared hubs. It weighs in at 1.67 kg or 3.67 lbs. It is one stiff mechanism. I ran it in on a lathe to warm it up at some high rpm (well, not high for a stud like me…only about 1000 rpm) and after that it ran a little more smoothly. I can’t feel any backlash but I will have to get a crank and a wheel on it to measure that with any accuracy. Now it’s off to the wheel builder and then onto the frame. Pictures will come later when I build the second one because it won’t be filled with grease.
Is there some gasket or sealant that keeps the grease in? That’s some daring way to break in the mechanism! Talk about confidence! BTW: why were rods used to covey force through the hub halves, and not a second set of bolts? How stiff does it feel- is much force required to start it turning- or can you easly turn it with a finger? Was that a run on sentance?
The surfaces are machined flat enough that no grease leaks out.
The rods (dowel pins) are accurately ground, hardened steel and are much better for locating than bolts. They won’t wear as quickly because they are so tight.
It felt VERY stiff before running it in. Now it feels…tight. It’s heavy at 3.67 lbs so it takes abit to get it going with just your finger. That will probably change after a wheel is laced onto it with all of the wheel and tire mass out at a large radius.
My excitement in this project was somewhat lessened when I saw this picture:
Look at the SIZE of that slide rule behind Harper! I would estimate that the hub is little more than a centemeter wide, and that the manufacturer is, in fact, a Leperchon.
I almost spit coke all over my monitor on this one. (For you other southerners out there, the type of coke I was drinking was Coke.) I fell out of chair on this one. Nice one, Chris!
The joke was only slightly weakened by your failure to spell leprechaun correctly.
Would you object to me submitting the image of you and your device to the Pointless Waste Of Time Stupid Caption Contest? I don’t know that they would use it, or when they would if they did, but it would make a great image, I think.
Could you include at the top of the EpiCyclic Hub page a short mission statement?
I haven’t been following the threads too closely, and I have not invested any time in looking at the drawings and pictures to be able to figure it out. However, it would be nice if you define Epicyclic Hub at the top, just so everybody is clear on what it does.
Too Lazy To Study The Specs Just To Figure Out What It Does,
> Harper, > > Could you include at the top of the EpiCyclic Hub page a > short mission statement? > > I haven’t been following the threads too > closely, and I have not invested any time in looking at the drawings > and pictures to be able to figure it out. However, it would be nice if > you define Epicyclic Hub at the top, just so everybody is clear on > what it does. > > Too Lazy To Study The Specs Just To Figure Out What > It Does, > > Lewis > > – > Animation > Posted via the Unicyclist Community - http://unicyclist.com/forums
> Harper, > > Could you include at the top of the EpiCyclic Hub page a > short mission statement? > > I haven’t been following the threads too > closely, and I have not invested any time in looking at the drawings > and pictures to be able to figure it out. However, it would be nice if > you define Epicyclic Hub at the top, just so everybody is clear on > what it does. > > Too Lazy To Study The Specs Just To Figure Out What > It Does, > > Lewis > > – > Animation > Posted via the Unicyclist Community - http://unicyclist.com/forums
So, are you going to clue me in as to what your hub actually does? I have been looking through old posts and I haven’t found an explanation.
See, I have the pic of you with the hub as my desktop, but I can’t explain what the hub does. I just have to tell them that’s a leprechaun with a compass.
The planetary (epicyclic) geared unicycle hub is a transmission designed specifically for a unicycle. The goal is to gear up the wheel revolution to crank revolution ratio. In this case, that ratio is 1.5:1. That is, for every revolution of the pedal cranks, the wheel will make 1.5 revolutions.
For my prototype unicycle, I am having a 24" wheel built. With the hub gear ratio the effective diameter of the wheel will be 36". I chose the 1.5:1 gear ratio because it will make a very common unicycle wheel size (24") appear to ride like a 36" wheel, another size with which many unicyclists are now familiar. This similarity will be in speed and cranking effort only. It will not reproduce the comfort and esthetic advantages of having a large diameter, pneumatic tire to smooth out bumps and road irregularities and look cool.
I live in Seattle which is about an hour away from the site in the Snoqualmie Valley where both the NUC 2002 (now NAUCC?) and UNICON XI conventions will be held. I will have a geared prototype unicycle available for anyone to ride there. I will have a variety of seatposts with saddles mounted for people of various sizes. It will be an ideal place to have people from all over the world who have ridden both a 24" and 36" wheel test this geared prototype. I will have a second hub partially assembled as a visual aid and also a set of D-size drawings showing each part and its dimensions and a cross-sectional view of the assembly. These drawings (*.gif versions) are already posted on my web site.
In past threads a number of gearing schemes have been discussed. These include chain driven models, outside gear driven models, and modified Sturmey-Archer hubs. In fact, the Sturmey-Archer web site provides a good overview of the operation of planetary gear systems. All of these approaches had some drawback. The chain driven systems suffered from backlash due to the inherently slack nature of chain drive. Outside gear sytems required odd and necessarily shaky locations for split crank assemblies in which two short cranks must be attached, one to each side, of the fork. The modified Sturmey-Archer hubs were cluges of parts designed for another function altogether being forced by welding, filing, bending, and machining to become geared unicycle hubs.
Having read these threads I decided to design, from the ground up, an internally geared hub based on the epicyclic principle (again, Sturmey-Archer and automotive transmissions) specifically for a unicycle in order to avoid the pitfalls of the other methods. In this design there are a few important requirements to meet. The drive component must be integral with the unicycle axle so that the axle may go all of the way through the hub for strength. The gear ratio must be greater than one (the difficult one in this case) because the goal is speed. The hub must be as compact as possible. Any gears or bearings used must be stock items that are available off the shelf and reasonably priced. Naturally, all of these requirements conflict and the finished product is to some extent a compromise. But such a pretty compromise it is.
Lewis,
I thought this has been explained already. But anyway, Harper’s epicycle
hub is designed to give a unicycle a 1.5:1 gear ratio. For example, a 24"
wheel with the hub would effectively be geared to 36" (or 36" to 54").
The purpose is to give unicyclists a mechanical advantage that will
increase speed. (Harper, correct me if I’m wrong!) It probably won’t work
for muni, but for commuting it would be great because a geared 24" takes
up much less room than a 36" Coker.
Jeff
On Thu, 14 Feb 2002 18:37:22 +0000 (UTC) Animation
<forum.member@unicyclist.com> writes: > Harper, > > So, are you going to clue me in as to what your hub > actually does? I have been looking through old posts and I > haven’t > found an explanation. > > See, I have the pic of you with the hub as my > desktop, but I can’t explain what the hub does. I just have to tell > them that’s a leprechaun with a compass. > > So, please, fill me in. > Lewis > > > > > – > Animation > Posted via the Unicyclist Community - http://unicyclist.com/forums >
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Lewis,
I thought this has been explained already. But anyway, Harper’s epicycle
hub is designed to give a unicycle a 1.5:1 gear ratio. For example, a 24"
wheel with the hub would effectively be geared to 36" (or 36" to 54").
The purpose is to give unicyclists a mechanical advantage that will
increase speed. (Harper, correct me if I’m wrong!) It probably won’t work
for muni, but for commuting it would be great because a geared 24" takes
up much less room than a 36" Coker.
Jeff
On Thu, 14 Feb 2002 18:37:22 +0000 (UTC) Animation
<forum.member@unicyclist.com> writes: > Harper, > > So, are you going to clue me in as to what your hub > actually does? I have been looking through old posts and I > haven’t > found an explanation. > > See, I have the pic of you with the hub as my > desktop, but I can’t explain what the hub does. I just have to tell > them that’s a leprechaun with a compass. > > So, please, fill me in. > Lewis > > > > > – > Animation > Posted via the Unicyclist Community - http://unicyclist.com/forums >
GET INTERNET ACCESS FROM JUNO!
Juno offers FREE or PREMIUM Internet access for less!
Join Juno today! For your FREE software, visit: http://dl.www.juno.com/get/web/.
I have been looking through old posts and I haven’t found an explanation.