Frame Design

Unicycles and Equipment
1

Hi all,

I’ve been working on a frame design and would like to get some
collaboration going to either refine it or junk it and start in another
direction.

There’s a jpeg of it at my novice web page:
http://home.mmcable.com/masseyhp/doug/page1.html

The one I have really been working on is the aluminum I-Beam design. So
far it is at 745 grams. If anyone is interested in seeing it better, a
viewer can be sent out with it so that you can rotate and zoom.

The I-beam style was chosen because of trying to balance the high loads of
the frame with being lightweight. I-beam technology is a very proven type
of construction. the inside profile can be conformed to a specific
tire/wheel combo.

If the design is refined in aluminum, then it could be converted to carbon
fiber for even less weight.

The load directions that were considered were imagined being input thru
the seat and resulting in bending, twisting, etc. of the frame. Forces
thru the axle/bearings would be the opposing forces.

Seat loads: Vertical (up, down) Lateral (left, right) In-Line (fore, aft)
Pitch (up, down) Roll (left, right) Yaw (cw, ccw)

Besides the vertical down load, I believe the next greatest load is
lateral that would push the frame into the tire. These two loads should be
far greater than any others. That is the reason behind the I-beam versus
round tubing.

The disadvantage is the possibility of hitting the geometry with a knee.
For this reason, the frame is tapered in and very narrow at this point.

Any feedback would be appreciated

Doug Massey Norman, Oklahoma

2

Doug-

The taper you mention I assume is the slight one close to the crown to reduce the width there. It still appears to have a very wide, flat crown for a good footrest. It also looks like you have opened up the inside of the frame there to accommodate a fat tire which could be easily inserted when deflated.

The aluminum alloy is 6061, not 6160. If you are machining from a single billet, I would recommend the tougher, but not so weldable, 7075 series. Scott Bridgman, the Muniac, at

is the guy to banter with about aluminum frame design.

3

yes, 6061, my bad.

Since it can be built without welding, maybe the 7075 would be better.

Thanx

Doug

“harper” <forum.member@unicyclist.com> wrote in message
news:a0nrer$d11$1@laurel.tc.umn.edu…
> Doug-
>
> The taper you mention I assume is the slight one close to the crown to
> reduce the width there. It still appears to have a very wide, flat crown
> for a good footrest. It also looks like you have opened up the inside of
> the frame there to accommodate a fat tire which could be easily inserted
> when deflated.
>
> The aluminum alloy is 6061, not 6160. If you are machining from a single
> billet, I would recommend the tougher, but not so weldable, 7075 series.
> Scott Bridgman, the Muniac, at
>
> http://www.muniac.com/
>
> is the guy to banter with about aluminum frame design.
>
>
>
>
> –
> harper Posted via the Unicyclist Community -
> http://unicyclist.com/forums

4

It’s good to see some new frame designs. My initial reaction is “Would it
be economical to machine the entire frame on a CNC mill?”. If you’re
making the frame for yourself and the machining time is free then
machining costs are not an issue. But for production work that would
probably be a very expensive frame. You also might want to consider split
block bearing holders. It looks like the current design is relying on
pressing the bearings into the frame. That would make inserting and
removing the wheel almost impossible. Make sure you can fit a DH rim like
the Sun Doublewide in there. It looks like it gets real narrow in the
middle of the fork which might make inserting a fat DH rim impossible. But
enough of the critical comments. Looks like an interesting frame.

john_childs

>From: “Doug Massey” <dvm@mmcable.com>
>
>Hi all,
>
>I’ve been working on a frame design and would like to get some
>collaboration going to either refine it or junk it and start in another
>direction.
>
>There’s a jpeg of it at my novice web page:
>http://home.mmcable.com/masseyhp/doug/page1.html
>
[snip]

Chat with friends online, try MSN Messenger: http://messenger.msn.com

5

I think on the posted drawing Doug specifies that the bearing holders are not finished or separated. I took that to mean that the design of that detail is not yet complete.

6

“John Childs” <john_childs@hotmail.com> wrote in message
news:mailman.1009767929.26685.rsu@unicycling.org…
> It’s good to see some new frame designs. My initial reaction is "Would
> it be economical to machine the entire frame on a CNC mill?".

Yes, it would be expensive. I went back and looked at individual
features. The most prohibitive, costwise, would be the seat tube
machining. So that will have to go. Maybe mechanically lock in a carbon
fiber tube in that area?

I’ve since converted the I-beam style into steel to see what the weight
comes out to and posted that on the web page. 801 grams.

Thanx for the comments. There’s no such thing as failure, only feedback.

If anyone would like some help getting components drawn up, I’d be happy
to help. Full assemblies get real tedious.

Doug

7

ok, i am a dumb arse, well pretty much anyway. And as such i have no idea about design and building a unicycle that will actually work and big strong in design, yet light etc… basically perfect for me. With the rather large realisation that getting a uni custom make is actually kinda tough, does anyoine have any suggestions? and or design? this one looks fantastic by the way, it should be good. i can’t give intelligent feedback, cause i don’t know anything about this stuff.

Tim

I worship Jesus

8

> Besides the vertical down load, I believe the next greatest load is
> lateral that would push the frame into the tire.

Probably any frame is sufficient in covering the vertical down load, so
don’t worry about that. But what you may be missing is the “twist” load.
This was what caused a failure in my carbon fiber (Roger Davies) frame
before he modified it. A tremendous amount of left-to-right twisting goes
on as you pedal. This puts lots of pressure on the bearing area, and can
be a problem in frames that are not stiff against these forces. A tubular
frame (Sem XL for example) will be much more resistant to this force than
a stamped frame (Schwinn, Semcycle deluxe).

Your design looks very strong in every direction except possibly this one.
I also like the way you’ve fit it around a wide tire.

Good luck with your design!

John Foss, the Uni-Cyclone jfoss@unicycling.com www.unicycling.com

“If it weren’t for the last minute, nothing would get done.” - Kevin
“Gilby” Gilbertson

9

>
>
>
>The load directions that were considered were imagined being input thru
>the seat and resulting in bending, twisting, etc. of the frame. Forces
>thru the axle/bearings would be the opposing forces.
>
>Seat loads: Vertical (up, down) Lateral (left, right) In-Line (fore, aft)
>Pitch (up, down) Roll (left, right) Yaw (cw, ccw)
>
>Besides the vertical down load, I believe the next greatest load is
>lateral that would push the frame into the tire. These two loads should
>be far greater than any others. That is the reason behind the I-beam
>versus round tubing.
>
Doug,

A beautiful concept design. I agree that side loads are of primary
interest. How much side flex will this frame have when climbing a hill,
and how much tire clearance does that leave? What’s the maximum bending
stress in the fork leg under the same conditions?

I too wanted to make a tapered I-beam uni a year ago. It never
happened, though.

Chris