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<DIV><FONT size=3D2>Comox, B.C. “centre of the world”</FONT></DIV>
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<DVI><FONT size=3D2>While I’m typing what have those of you who build, =
or have=20 built, frames done for bearing retainers? Any advice or
comments on = pitfalls to=20 avoid?</FONT></DIV>
<DVII> </DIV>
<DVIII><FONT size=3D2>Cheers, Greg</FONT></DIV></BODY></HTML>
Hey Greg, i live in Black Creek, we should go for a ride sometime! I never
new there were any other unicyclists in town! )—(x) Dylan Wallinger Keep
Riding http://www.extremeunicycling-bcmat.cityslide.com
Bearing retainers are always the crux of framebuilding challenges. One
solution is to get an appropriate diameter of thick-walled pipe and cut it
into bearing-wide widths. Drill the walls thinner, leaving a small lip on
one end of each pipe segment to contain the bearing. Then cut the pipe in
half and weld bolt holes on each side of each unit to clamp the two halves
together. This unit gets welded to the fork stays- the major challenge
being to keep everything lined up properly when welding.
-Kris.
— Greg Moore <gmoore@island.net> wrote: > Comox, B.C. “centre of the world” > > While I’m typing what have those of you who build, or have built, frames > done for bearing retainers? Any advice or comments on pitfalls to avoid? > > Cheers, Greg >
I concure with Kris: it’s all about the bearing holders. The bore and leave flange method can be seen on the Hunter frame. Here is a link to the unicycle.com page for the Hunter…blow it up and take a peek at the flange. Notice it is only on the outside:
You can get the united type holder, and weld 'em on- but that more or less defeats the perpose of building your own frame.
I’m inclinde to fabricate something like Scot has here:
I have also considered building up sections from soldered silicate bronze, a method that is easly accessable, being done primarly with saw/drill/torch. This might not be an option if you are trying to make a very low weight frame.
You could bypass most of the machining (but not the weld needed to attach the bearing holder to the frame) by making the bracket from tubing, as Kris mentioned above, then inserting a small section of a smaller diameter tubing as a stop.
I’m glad this topic has generated some responses. I’m keenly interested in
the nuances of frame building having just started the design/construction
of my first fram.
Kris, I hadn’t thought of the pipe idea. How is the kerf acounted for
after the cut?
I’ve decided to machine the retainers for my first frame from aluminum but
it certainly is the long way around.
Has anyone thought of using molded FRP (fiberglass)?
Christopher points out the flange is only found on the outside of the
retainer. Is there a reason for this? My current design has a shoulder
both sides and if I need to make changes now is the time.
As far as pre manufatured retainers. That is waaaay too easy
Actualy, carbon fiber. I am designing the mold now. The first will be for a 36" wheel with aluminium bearing holders nested in kevlar or glass to prevent galvonic action with the carbon. Same thing for the seat post tube and break posts. I have some hesitation of integrating the bumper posts into the carbon fiber, so for now they will come off of the seat post. If I could get the rims for the right price, I would consider making the wheel from carbon as well- not panel spokes, but molded (we are, after all, talking about a low speed -25 mph- wheel) but would be dependant on finding a supplyer of quality custom rims at a resonable price. Also, the high tolerances involved in making a wheel might prove prohibitive.
I would apreaciate feedback on what features folks would like to see incorperated. If there is interest, I would consider production. Price point is a major issue.
Since the bearings are fixed to the axel, the bearings only have to be retained on each side of axel. Check out the design on the Miyata bearing holders:
Another option: I was recently looking at an industrial supply catalog
(McMasters?) and because of my unicycle-curious mind I looked in the
bearing section. They had high quality bearing holders with a small “lip”
that looked identical to the ones on the DM Vortex, and there were also
many other different kinds that could be welded to a frame. I think that
the company accepted small orders, too. I also found very high quality
bearings (17mm inner, 35 or 40mm outer diameter) that were inexpensive. I
think they were ABEC 5??? (the same as high quality roller blade bearings)
Jeff
On Mon, 29 Oct 2001 20:35:13 +0000 (UTC) rhysling
<forum.member@unicyclist.com> writes: > I concure with Kris: it’s all about the bearing holders. The bore and > leave flange method can be seen on the Hunter frame. Here is a link to > the unicycle.com page for the Hunter…blow it up and take a peek at the > flange. Notice it is only on the outside: > > > http://www.unicyclesource.com/Hunter_Cycle_Company_(2_styles)66184.html > > You can get the united type holder, and weld 'em on- but that more or > less defeats the perpose of building your own frame. > > I’m inclinde to fabricate something like Scot has here: > > http://www.muniac.com/emunitext.htm > > Take a look at the TIG welded frame. > > I have also considered building up sections from soldered silicate > bronze, a method that is easly accessable, being done primarly with > saw/drill/torch. This might not be an option if you are trying to make a > very low weight frame. > > You could bypass most of the machining (but not the weld needed to > attach the bearing holder to the frame) by making the bracket from > tubing, as Kris mentioned above, then instead of inserting a small > section of a smaller diameter tubing as a stop. > > Any other ideas? > > Christopher LeFay > > (last of the Mississippi Unicyclists) > > > > > – > rhysling Posted via the Unicyclist Community - > http://unicyclist.com/forums >
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> Actualy, carbon fiber. I am designing the mold now. The first will be > for a 36" wheel with aluminium bearing holders nested in kevlar or glass > to prevent galvonic action with the carbon.
Sounds like we’re working on parrallel projects Christopher though my
first frame will be for a 26" wheel.
As far as galvanic corrosion, is that an issue in the absence of an
electrolyte? High school chemistry is 15 yrs ago but if I recall a
galvanic cell consists of metals of dissimilar nobility or galvanic
potential connected electrically and immersed in the same electrolyte.
Carbon isn’t a metal so I’m not sure it can function as anode/cathode.
Anyone know? Carbon is a conductor though and could electrically connect
the aluminum seat post and bearing retainers with some other metal, the
bearings themselves perhaps in which case the aluminum would suffer. But
we’re still missing the electrolyte. A puddle or rain won’t suffice unless
it’s unusually acidic, basic, or contains dissolved salts. Few of us ride
in salt water and those that would have problems other than their cycles!
Dare I ask what you’ll be making the cranks out of?
Galvanic action is not limited to ideal situations. Galvanization between iron/carbon or aluminium/carbon is a serious cause of frame failure. Titanium would be better/more stable, but is prohibitively expensive. Some companies use a cheep solution of anodizing the aluminium, or a thin chemical coating on iron- and get what they pay for.
Carbon cranks would rock, but have the potential to come in contact with enviromental hazards; I am hesitant at this point to use carbon cranks.
A brief overview of do-it-yourself carbon bike production may be found here:
I’v got a couple of books on the subject coming by post, and will pass on the titles of those I find helpfull.
Thanks for the link Christopher. I had visited that page before and it’s a
good read. The decision to err on the safe side had been made and I’ve got
1.47 oz E Glass coming for a barrier but I still don’t understand the
chemistry involved. I probably never will and the barrier is cheap
insurance.
I hope you’ll post regarding your progress. I for one am very interested
in your project.
I’ve worked with carbon fibre in a limited way in the past while involved
in boatbuilding but now that I’m trying to engineer a fork, deciding on a
lamination schedule etc. with the loads involved being, for me anyway,
hard to quantify, I find I have an awful lot to learn.
I agrea: safety is a huge concern, and the only way to know how much is enough is by load testing. I want to know at what point the bearing holders will tair away from the carbon…or if the “tubes” will break before that ever happens. Erroring on the side of caution costs in weight and price, but is far better than the alternitive.
Fiber direction seems very important- I would definately take this into account when making lay-up decisions. The carbon is the structural element here, with the epoxy as a binder; high end carbon bike manufactureres brag about the low epoxy/carbon ratios they achieve (typical is 50/50 - high end 30/70 carbon). Allowing for excess epoxy bleeding off during lay up is important.
I’m focusing on mold design and referances this month; next month will be construction materials. I will post progress reports- positive and negititve- along with copious pictures and process descriptions.
I’m psyched to see what you do! What are you considering as far as basic fabrication? Prefab tubes? Foam core? Mold formed (Ummmmmmmm, smoooth!)?
> only way to know how much is enough is by load testing. I want to know > at what point the bearing holders will tair away from the carbon…or > if the “tubes” will break before that ever happens.
Here’s a little input from a non-builder. I have a Roger Davies carbon
frame, and it came to my attention that the biggest stress on this frame
in normal riding is the twisting force in the tubes. When Roger built my
frame, the tolerances were so tight in the lugs that apparently nearly all
the glue squished out when he put the joints together, because the air
couldn’t get out. So when riding on a steep trail, my fork leg twisted in
the crown lug, and I had to walk out.
Amazingly, even though the joint had become ungluded, the fit was so tight
I couldn’t twist the tube back into place with all my strength. Pedaling
forces are very high.
Roger upgraded my frame with air holes to let the adhesive out, and
aluminum pins to keep the joints from twisting. But when riding I am now
very aware of the amount of twisting force that goes through the whole
frame with every hard turn of the pedals.
