I’ve been reading through this, all I can say is that is sounds great, especially for road/distance riding.
Good luck with it all!
How will control be maintained forwards/backwards? From what I’ve read it will just coast with the cranks horizontal plus a little bit of play. Could backwards pressure be applied gradually so that it would act as a brake (and vice versa when coasting backwards)?
Once/if you start producing these I’d definitely be interested in buying one.
Thanks.
With a typical freecoaster hub, if you are coasting backwards on it and you pedal forwards, it will engage and cause you to pedal backwards. Depending upon the speed at which you are moving backwards will depend on how hard the cranks will engage, I have been thrown off my BMX by a freecoaster engaging, but I had just aired 6’ out of a 6’ quater pipe and come down backwards to coast away.
Control of the hub will obviously be easier at slower speeds, and at greater speeds could pose a problem. If someone were to use a freecoaster uni hub on a road uni, chances are that they would have a brake anyway thus taking care of the problem posed by slowing the wheel through the cranks.
To be honest, top priority at the moment is to get the hub working, and fix any problems / potential problems from there. I will add however, that freecoaster hubs were developed from coaster brake hubs, the basics of the development is that the brake pads were removed, allowing the hub to rotate freely in either direction when the drive is not engaged. That said, if anyone testing the hub suggests it could do with more controll at the cranks, as you said by applying gradual pressure on the cranks in the opposite direction of travel, there is no reason why the hub could not be designed to fit brake pads.
yes the brake pads idea sounds good and it could be possible to make something up on a lathe like this so the axle widens at the ends to incorporate isis or splines.
It has to be two or three part if you want to be able to put it through a 17mm hole.
This hub
http://americancycle.com/itemdetails.cfm?id=2455
has a 20mm axle, which you could get a square taper axle through - but not quite an isis axle. It also is built for external separate poky in axle bits, so if you could make a similar part to their axle ends, but with a splined end, then you wouldn’t have to mess with hub internals.
Joe
I e-mailed George at G-Sport, for those who have no idea who G-sport are, they make top notch BMX parts. Seeing as I have heard of a freecoaster in the works on a few occasions, I figured why not ask them. Anyway, he had a look at this thread, and had this to say on the matter.
''I can pretty much follow your idea from that I think.
Feel free to post any of this on that thread if you want.
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The biggest issue (though not insurmountable) is how you provide “resistance” for the clutch element(s). On ANY freecoaster, you need to provide a way for the hub to “know” when you are pedaling. With an ordinary freecoaster the clutch element is loosely held by a spring relative to the axle, so when the driver advances RELATIVE to the (stationary) axle, and the clutch element is being loosely held to the axle, the two can screw together and engage drive. Without this element the cranks can just spin and take the clutch with them at it’s un-engaged spacing. You can get over this by running some sort of stationary element in from the side, but this will obviously conflict with the existing large bearing which I imagine you had intended to use as your main hub bearing…
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Assembly. As I think you realise, the clutch element is larger than the hole in the drive side of the hub shell and has to come in from the other side, so fixing two half shells together will leave no way to insert the clutch elements, you seem to be aiming to get round this by having the hub bolted together, which will work, but means disassembling the entire wheel (spokes and all) to do anything inside the hub.
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Bearings. If you have to remove the driver to shell bearings to get a friction element through to the clutch elements, then you need to put the main hub bearings inside/between the two clutches and there isnt much space left there.
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The stresses are actually HIGHER due to the 1:1 drive ratio than they would be on a geared up BMX, combine this with the “crash” engagement that you are likely to get using the unit to slow down and the loads will be pretty big (though it probably could be designed to work).
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If you use current parts, then you will be restricted to a main crank axle diameter of about 15mm which is simply not strong enough IMO… And those threaded parts are not straightforward to make if you “simply” want to make them in a larger size…’’
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This is the biggest issue with this idea, to go with this particular idea, the lack of resistance for the clutch mechanism to act upon poses a big problem. One solution would to be to have one side of the hub driven, and the other side the frame would clamp on to a static axle. I had realised this, and I am trying to think of a solution allowing me to use my initial idea.
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This is a fair point, however, the drawings I am working on show a single piece hub shell, my idea being that the ring that the clutch engages with is to be ‘‘top hat’’ shaped with allen bolts to secure it, rather than ring being threaded and a pain to remove.
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This is dependant on on whether I can figure out a solution to problem 1 which allows me to use the initial idea. If I can’t use the initial idea, then i have to work with this.
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Not sure what so say regarding the loads being greater. As for the slowing of the unit, brake pads could be the way to go.
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I had planned on using parts that are avaliable now. One thing to do would be to test some with parts that are avaliable now, and try some with custom parts.
This would encounter tha problem of having no resistance in the system. Not to mention that the studs are threaded, so the cranks would essentialy be screwed to eachother vie the axle.
Big G’s such a dude!
Neat idea, Im looking forward to the outcome of this.
Edd
Yep. And cheers. It’s gonna take a while, but it will work.
Searching these forums, I found the following thread:
Containing the following link:
I have mailed Kevin Jones, the guy who created and is riding the unibike in the vid, though he hasn’t been on myspace for a bit. I also mailed the person who posted the vid, asking if the hub was able to drive the bike in either direction and coast in either direction, and I am told that it does.
If Kevin’s attention could be brought to the matter of the hub being used in unicycling, we could potentially have access to a freecoasting unicycle hub that has already been designed and ridden. If not, then It may be a bit longer, but I’m still plodding away at it.
Currently, I am trying to figure out how to get a static element in the hub, to create resistance for the clutch mechanism. I have drawn an idea on how to have the clutch mechanism operate in both directions off of one driver, which will take up less space and weigh less than the having the mechanism operating on two drivers. Though, at the moment, getting a static element in the hub from the side of the hub that the clutch will not be, while keeping the cranks aligned, escapes me at the moment.
Scrap that.
Pic of internals of intended hub.
I knocked up a drawing on paint, not great, but it does the job.
The main part of the axle will be 20mm. The part of the axle on the right of the drawing, that I have drawn as seperate, I am wondering if i should have that as part of the axle, or as a seperate piece held on with a nut. This larger piece will be the driver of the freecoaster.
The driver, will be threaded at the point on the drawing where it sits inside the clutch lump, and the clutch lump will be threaded on the half that sits on the driver. The clutch lump will engage with the clutch plates, the left most if the axle is driven forwards, and the right most if the axle is driven backwards.
The static axle will be clamped in the bearing clamps, with two different size needle bearing units inside for the normal axle to run on, and one cartridge bearing unit on the outside for the hub shell to run on. The clutch springs will sit on the static ‘‘axle’’, and will push against the inside of the clutch lump to creat the resistance needed for the freecoaster to work.
I recon that I could get the internals working, including the hub body bearings, in a space of 75mm. The hub will have the typical 100mm bearing spacing.
Anyway, that’s the basics of it, now I want your thoughts on it, so be cruel.
Yeah, although I am not sure on the workings of the clutch and normal free coaster hubs its looks like it should work, and it looks very similar to the geared hub I was disassembling on my shed.
Hopefully this will explain.
with the new sym cranks, this hub could take flatland to new levels. Since with coasting you probably won’t be doing too many crank rolls, the sym cranks would be the ideal cranks to have when coasting and standing on the cranks for flatland.
definitely going to get one of these (36 or 48 hole) when/if they start getting somewhat reliably produced.
Yeah, sound’s a plan. I was thinking of the Sym cranks for ramp, I think they’d work well.
I have re-drawn the hub, well everything but the axle, as I’m still deciding whether to go one piece or two piece. It will be one piece connecting the cranks, at around 20mm straight through, but I can’t decide whether to have the driver as part of the axle, or to have it as a second piece. I have all the bearing sizes, so the bearings are in the drawings. I have a couple of people I want to look over the idea and drawings, then I’m going to shop about for quotes for one, and for five complete hubs soon, and obviously go to the place that offers me the best deal.
I’ll post up any progress as and when it happens, could be over any ammount of time really.
How much movement would would people like at the cranks between forward and reverse engagement?
25 degrees of crank movement will give about 1mm clutch movement, going by the thread pattern on a freecoaster driver and clutch. Would anyone want more movement in the cranks?