I can now relax a little bit because I’m about to order the rim, tyre, video and stiffener plate from unicycle.com (I know I’m taking ages but I’m waiting for a quote because I’m using Mum’s credit card). Also, my frame is all sorted and ready to build. Here is my progress report…
Bearing Holders - The frame builder I’m using doesn’t have the equipment to machine some bearing holders so I’m getting this old guy who works at home in a one-man business called ‘Timeless Engineers’ (which is pretty funny if you’ve seen his work place) to make me a set of bearing holders. I was surprised that it’s going to cost me $60AUS for just the bearing holders which is reduced from the normal $150. Anyway, it’s my only option at the moment and I’ve got nothing to complain about really. They’ll be done in about 5 or so days.
Frame Crown - This’ll be like it’s drawn in the old plan of the frame at http://www.unicyclist.com/gallery/albun59 . It’ll be two ovalised 4130 chromoly legs joined over the top by a flat 10mm thick piece of metal with bits on the side for support. I’m a bit worried that this’ll be too heavy but he was worried about strength and wanting to have something this thick. Do you think it’ll be too heavy? I suppose most of the weight is in the wheel and not the frame.
Seat Post Bit - This’ll be made to fit a 22.2mm seat post. I don’t think this’ll be a problem because if I ever get a seat with a larger diameter seat post I can just get him to make me a smaller seat post. This was the only size he could get for this bit. Will I be able to find any good quality seat post clamps in this size?
Clearances - This frame will be able to fit a 24" x 3" tyre with 5mm side clearance at least and ample top clearance. It hopefully won’t be too big for one-footed stuff. I’ve worked out that it’ll also be able to fit an average sized 26" tyre with ample side clearance and about 5-10mm top clearance. The 26" wheel isn’t actually much bigger than the 24" wheel at all (not 2" bigger). I’m also positive that the frame will fit a Profile hub.
Powder Coating - I think I’ll leave this until after my 4 week holiday on Christmas Day. When I do get it done (I still might have it done before the holiday) I’ll have it painted in a nice metallic orange as close to the colour of the KH24 as possible. I actually knew exactly what colour I wanted (that orange) before I saw the KH24 and it was a real relief to discover that this colour would work really well on a unicycle frame.
Overall Cost and Time - Ian (the frame builder) said it’d be about 3 hours of building time and if I can give him the bearings early next week he’ll hopefully have it done by the end of next week. This is the first bit of good news I’ve had in a long time. It’ll cost $60 for the bearings plus $232 for the rest of the frame (how’s that for a rough estimate).
I’ve also had some good news about the things from unicycle.com. It looks like I will recieve them by Christmas with any luck. They actually use the Express mail and have been really nice to me.
I’m excited!
Andrew Carter
Re: Custom frame - finally some good news
Is it a solid 10 mm slab of metal? If it’s solid it is way too thick and will be way heavy. You could use hollow tubing instead. The KH uses a flat piece of metal for the crown and it is not anywhere near 10mm thick.
You could also save some weight by using flat metal gussets instead of the angled tubes. It would involve less welding and less metal. The KH muni uses flat metal gussets. I don’t know if there is a good picture somewhere of the crown of the KH muni. If there isn’t a good picture around I can take a picture of mine tonight.
John,
Thanks for that. What size would you recommend for the flat bit? I tried to tell the framebuilder that frames don’t seem to need things that strong but I don’t think he’s convinced. Can anyone please give me some points as to why frames don’t have to be that strong? I suppose when you do any drops or things like that you land standing up and the bearing holders would only really have to be strong wouldn’t they? A photo of the crown of the KH24 would be great thanks. What are flat metal gussets? I’ve decided on 4130 chromoly tubing. Should the whole frame (including the flat crown bit) be made of this? And finally, how heavy should the frame be?
Thanks a lot,
Andrew
Here’s a photo of the crown on the stainless frame I made a few weeks ago:
http://www.unicyclist.com/gallery/albun90/aaj
The flat bar that makes up the crown is 1/4" (about 6mm) thick and is way strong. If I would have had some 3/16" (about 5mm) thick material I would have used that instead. The gusset that John mentioned is the piece that’s welded to the top flat bar piece and the fork legs. It has an arc on the bottom to clear the tire. The gusset piece that I used is thin … I think #14 gauge sheet metal or about 1.8mm thick.
The 1/4" flat bar with gusset is VERY strong - way stronger than it has to be. The gusset not only strengthens the top flat bar but also reduces (or eliminates) flex at the crown/fork leg junction. I would see no reason why any of the crown parts need to be CroMo material.
If I remember correctly, the stainless frame weighs 1280 grams (2.8 pounds) … that’s heavy. I just weighed two CNC machined aluminum frames I have. One weighs 1024 grams (2.2 pounds) and the other weighs 844 grams (1.8 pounds). My old Sem XL skinny crown frame weighs 1040 grams (2.3 pounds).
Steve Howard
Unless you can build a frame yourself ala Steve Howard, I think it is advisable to find a builder with unicycle building experience. Almost every account that I’ve read about where this is not the case has the left the buyer with mixed feelings and they end up spending more that they would have had they had gone with an established uni builder.
It seems as though the inexperienced or first time uni builder will overdesign and over-analyse areas that the old pro doesn’t give a second thought.
I have followed your saga and hope that you are very happy with the end result.
Have a look at the MUNIAC website and read Rod Wylie’s account of his custom made MUni in the section titled: “empirical uni” .
If you haven’t already, print out the photos from the link that “showard” has provided and show them to your builder. They should give him plenty to base a solid design on.
Good Luck!
Steve,
Thanks, I forgot about your frame. I really like the look of that gusset. If you don’t mind I’ll copy that idea for my frame. Is it on the front only? Also, is that frame so heavy just because it’s made of stainless steel or is it also because of the design and thicknesses and so on? I’ll print out those photos and what you said in your reply and show them to Ian (the framebuilder). That frame really does look nice, well done.
Frank,
Unicycle frame builders or people who have built unicycle frames before are quite rare here. Ian has actually built a frame but it was for a giraffe. He’s a really nice guy and very good to work with. I will make sure I get the metal slab bit down to about 5 or 6mm and add a thin gusset. Will the gusset add much weight? I suppose it’ll be lighter than those bits that I was going to put on. I’ll be sure to post heaps of pictures and comments when it’s all done.
Thanks a lot everyone, I really appreciate the help.
Andrew
Andrew,
I guess it’s easy to take it for granted when here in the states it’s relatively easy to just buy a Hunter or something through Uni.com. without the shipping costs killing you.
I’m sure that Ian, your builder, will do a good job, especially if he can see up close photos of proven frame designs.
There are also a couple of up close photos of the new KH frame that “Monty” put up on his webshot pages. Just do a search with Monty as the poster. The one titled KH photos, or something close to that, has a link.
I have uni’s with conventional hub/crank setups and one with a Profile. The difference is really amazing, the stiffness of the Profile setup will knock you out. There is no wasted motion or flex anywhere.
I look forward to seeing your photos.
By all means! After all, I stole the gusset idea from the KH24 frame! The gusset is only on the rear since the top flat bar piece slopes down toward the front … another idea stolen directly from the KH24 frame.
Stainless steel, carbon steel, CroMo, etc. all weigh the same (in practical terms). My stainless frame is heavy because the flat bar I used for the crown, at 6mm thick, is still about twice as thick as it needs to be. Had I used 1/8" thick (about 3mm) flat bar I would have decreased the overall weight by 90 grams. The bearing holders that I used are also much heavier than they need to be.
Good luck with the new frame and post plenty of pictures when it’s done.
Steve Howard
Re: Custom frame - finally some good news
You’ll be able to find good seatpost clamps for a 22.2 mm seatpost. It’s a standard 7/8" BMX size.
Unfortunately I don’t know of any aluminum bike seatposts that are 22.2 mm. There are steel BMX seatposts for 22.2 mm like the Primo Rod and others. The steel posts are heavy. If possible find a seatpost that uses alloy guts instead of steel guts to save on weight. The guts are the parts that clamp on the rails. Alloy guts are available after-market for posts like the Primo Rod. On other posts the alloy guts come standard.
I would suggest getting the neck of the unicycle made as long as possible so the seatpost clamp will be a couple of inches below where your seat will be. This will let you cut off much of the heavy steel seatpost to cut down on excess weight. I’m pretty sure that the steel seatpost will weigh more inch for inch than the neck of the frame. So making the neck of the frame as long as possible and keeping the steel seatpost as short as possible will minimize the weight of the uni. Keep in mind that you’ll need a reasonable minimum insertion length for the seatpost so there is a limit to how short you can make the seatpost.
Frank,
I’ve seen the photos of Monty’s KH frame. They were really helpful in the design of my frame. I rode my friend’s unicycle with the Profile setup and it really is stiff isn’t it. It felt great!
Steve,
Thanks. I’ll use that gusset idea on the back but I don’t think I’ll add the sloping crown. I need the frame to be built pretty soon which it will as long as it isn’t too complicated. I’ll go for a 4mm or 5mm flat bit. I think that although my new unicycle will be quite heavy, it’ll still be easier to hop with than my current one because it’ll have a 24" x 3" tyre (Gazz) and an Alex rim. I can’t wait!
John,
That’s a relief about the seatpost clamps. I knew I could find some sort of clamp but I do want a good quality one to match the quality of the rest of the unicycle. I’m not using a rail adapter or anything like that yet so I’ll have to put up with the Miyata seat post unless I really want to have a lighter one made. The Miyata seat seems really light to me compared to my previous Viscount. How long would you suggest the neck of the frame should be? At the moment it’s set at 150mm.
Thanks everyone for all the help,
Andrew
The length of the neck of the frame depends on how long your legs are, what size cranks, how thick the padding is in the seat, rails or no rails below the seat, and what your comfortable seat height is for muni and trials.
To figure out how long you should make the neck will require some measuring and a little addition and subtraction.
You already have a uni that you’re using for trials and the seat is where you like it. Measure the distance from the pedal in the lowest position to the saddle. Now do some addition and subtraction taking into account the height of the crown, length of cranks, thickness of the padding in the seat, etc.
Size it for putting 170 mm cranks on and for a thick overstuffed saddle and the possibility of adding rails later. Allowing for 170 mm cranks will require a little less than an inch, allowing for a thick overstuffed saddle will require about an inch, and allowing for rails will require about an inch. After taking all that into account put the top of the neck about and inch or two below that. Hopefully after all that the seat will still be above the crown.
Re: Re: Custom frame - finally some good news
That’s the diameter of a bicycle handlebar on the outside. You can probably get free alloy handlebars at the bike shop (ie broken/bent ones) and then just cut off the bit that you need. You will need one of those BMX style clamps that fit over the top to attach the post to the seat. That’s what I’ve done and it seems to be holding up so far- if you don’t have too much exposed seatpost then it should be pretty strong. You won’t get much length out of it anyway.
Ken