As some of you might know, I’ve been working on a Muni frame design for several months and prototype #6 has just been completed. I’ve updated my “gallery” photos to include a couple of new pictures of it along side prototype #2. The gallery is located at:
I DO have hopes of offering this frame for sale - most likely through unicycle.com - after it’s been determined if the thing is any good.
The original design considerations were simply this:
must fit a 24 x 3.0 Gazz tire
reasonably light
good quality
strong/durable
inexpensive - about $100.00
1,2 and 3 have been successful - #4 is unknown and #5 is a failure. I built three of the latest design hoping to get a good idea of how much time it takes to make one. There are about 7 hours labor in each frame and $40 in materials. My normal shop rate is $40/hour so the cost is more than 3 times what was hoped for.
I’ve been riding prototype #2 for a couple months with no problems - the screwed on fork blades haven’t come loose and the bearings haven’t moved in the flangeless pinch type bearing holders. I’ve increased the fork blade thickness from 3/8" to 1/2" and that seems to have really stiffened the frame up.
The latest three frames have been anodized rather than powder coated, have 27.2mm seat tubes and the thicker fork blades. The frame weighs 2.1 pounds.
There’s also a prototype hub installed in the latest frame. It’s made from 3/4" diameter high strength stainless steel with the flanges welded directly to the axle. Detailed photos of the axle are located in the same gallery as the frame pictures. I just got it all put together but haven’t tried it yet.
When I first started on this project my shop was very slow but that has changed. We now have a huge amount of work (food processing equipment) and my partner is in Ireland right now getting more! I’ll keep working on the Muni though, as time permits.
I wouldn’t call #5 quite a failure. While it is well over the $100 goal that was set, it still may be appropriately priced for a hand made frame.
Here is my thinking (note my limited knowledge of different Muni prices). I am going to guess at some of the figures.
Lets take my Sem XLW that I bought for @$339.00. The frame on that costs $55.00. If I take that off the top, then the parts costs me $284.00. If I add the $320.00 for Steves frame to that, my total cost comes to $604.00.
If that is the price for a Muni that is light weight, strong and takes a 3.0 Gazz then I think Steve is doing pretty well. This gets under the Semcycle Delux Muni @ $620.00 and well under the Hunters by several hundred. For a tighter comparison to the Semcycle Delux and Steves Muni, this assumes that the frame weights are similar. They may not. Finally, Unicycle.com does not list the price of the Semcycle Delux frame on their website. That would make comparing easier
IMHO, there is a hole in the midrange for a variety of Munis. There are comparatively more at the high end than at the mid range.
Was the cold connected crown design inspired by your 5th objective? While it is an eligant solution, I imagine it must suck a good number of those hours (BTW: is the neck reduced on the OD where it enteres the crown, holding the neck with the bottom flange?)? Aside from a lack of flexibility in changing wheels, the bearing holders are just plain inspired- simple and apparently effective at meeting Goal #4 and 5. I’m jelouse!
Is the 7 hours for a one off, or the per frame time in a full production run?
I think Tiawan will be filling the LOW end frame gap for 3" wheel sets soon. If production costs could be reduced by only a third, I think you would have a wonderfull contrabution to the mid-range frame catagory… and judging from the feedback here, a desireable ‘high’ end frame, as is- people just plain want it.
BTW: have you given up on the cammed crank design? Last we heard the protype crank had busted at the axel…?
Thanx for sharing your design process and progress- I look forward to your posts.
The cold connection design of the crown is definately a cost cutting measure. By pressing rather than welding, the individual parts retain their original “T6” heat treatment specs thus eliminating a re-heat treating step. I stole the idea from the bicycle fork makers; the steerer tube is pressed into the fork crown.
There are two things that affect how I’ve built the latest version: seat post diameter and overall finish.
Seat post -
I do not like 22.2 mm seat posts! My first uni is a SEM XL and I’ve ALWAYS had trouble keeping the seat post from twisting in the frame. The first couple prototype frames I made also used 22.2mm seat posts and I’ve had trouble with them twisting as well. I think stock steel uni seat posts are soft. That in addition to the smaller diameter (less contact area, less mechanical advantage to resist torque) spells trouble … not to mention they are heavy, don’t allow seat angle adjustment and aren’t particularly inexpensive. For all these reasons I decided to switch to a 27.2mm seat post that is very common on bicycles.
But … I’ve not been able to find any kind of steel tubing that has a 27.2mm inside diameter so I decided to machine the seat tube from solid 6061 aluminum.
Finish -
The first couple frames I made were powder coated. This turned out to be a problem since the thickness of the powder coating wasn’t uniform were the fork blades attach to the crown. I had to hand sand/file the powder coating to a uniform thickness or the fork blades, when attached, were not straight with the crown. Changing the steel seat tube to aluminum allows anodizing all the parts rather than powder coating. Since anodizing doesn’t add thickness or change dimensions this seemed ideal.
BUT … My experience with anodizing AFTER parts are assembled hasn’t been good. They use a sulfuric acid bath and it seems to leach out of cracks like where the seat tube would press into the crown. It causes an ugly, non uniform finish close to the crack so I chose to assemble the seat tube in the crown after anodizing.
BUT … The seat tube is assembled with Loctite. To cure, Loctite requires at least one mating surface that it can react with. It won’t react with an anodized aluminum surface! Therefore I rough bored the crown in the CNC, had everything anodized, then finish bored (in a manual mill) the crown to get a bare aluminum surface for the Loctite. I know that Loctite makes a primer for non-reactive surfaces. If it works (I guess I’m kind of doubting it) then I could finsh bore the crown on the CNC thereby saving about 45 minutes labor.
WOW … that was the long explanation.
On a related note - earilier today I took the first ride on the new frame and hub. Nothing broke …
Do I understand correctly that you machined the tubing from a solid billet of aluminium? If so, you can get 1.25 OD 6061-T6 tubing with a wall thickness of .083", at $30.25 for a 72" length- enough for 6 frames, here:
That translates to a 27.5407 ID- perfect. It’s what I might use. (Please note that I came to these figures without the use of Greg Harper’s Giant Slide Rule- so it might be best if you did the math yourself as well. Or ask Greg to climb up on a chair or iddle his giraffe and do the arithmatic.)
You might consider the use of a resist on the aluminium that you wish to remain unanodized. If that isn’t practicle, the anodized layer can be removed with an etch, such as sodium hydroxide (NaOH). This may have the undesireable effect of minuetly changing the size of the part. If it weren’t for the flange on the bottom of the neck, you could just have the anodizer hang only the upper portion of the tube in the tank. NaOH is not people friendly- so be carefull and protect yourself.
I have a few ideas about alternitive crown designs with a nod to reduced production costs- I’ll wip some primitive CAD pics up and post 'em in a couple days.
hey there,i just noticed on the gallery page with your pictures,picture 4 of 6 (the uni in the repair stand)has what looks like it might be a custom seat attachment.its hard to see from that angle but whats under there anyway?
At $250-$300 your racy frames seem like a bargain to me. If you are considering making frames to order I would like to buy one of your lightweight frames made from 3/8 aluminum plate (my application is not for MUni) for my future 700c lightweight geared uni, anodized blue if possible. I’m also interested in a 22.2mm seatpost. If this is not absurd, I would like to discuss details and a price with you by this summer. You make the coolest looking frames!
What you see there is a seat post rail adapter I made. It’s the same idea as the Wilder seat post adapter but without the handle. I’ve added a couple of photos of the adapter to my gallery at:
Unfortunately, to use a bicycle seat post with a unicycle saddle some kind of adapter needs to be used. If only unicycle saddles had built-in rails like bike seats do …
Smily face but but I’m actually drooling