Question on Custom Frames

Hi

I am going to get a custom frame made I was wondering what people
recommend as a good material to make them out of.

As I see it I have three main options

  1. Aluminium
  2. ChroMoly
  3. Steel

This is for a Coker Frame, so I don’t think that it will be under a lot
of stress from hopping etc. I know the various pros and cons for each of
these when talking about a bicycle frame but I am not sure how different
it is for a unicycle frame as there are different stresses.

The other question I have is what sort of wall thickness and diameter
would you recommend for the forks and crown. The seat post stem is
obviously a fixed internal diameter, but I am still curious on the wall
thickness.

One last thing, I have machined bearing holders, they only have a lip on
one side, what is the general recommendation on the side that the lip
should be, inside (towards the wheel) or outside (towards the cranks).

Any help is appreciated.

Thanks

James (jimmy)

Unix: It’s not just “User-Unfriendly”:
it’s ‘Proactively User-Hostile’!


Re: Question on Custom Frames

> I am going to get a custom frame made I was wondering what people
> recommend as a good material to make them out of.

Cool - Who is making it if you don’t mind me asking, if you don’t
have a builder yet - email me

> 1) Aluminium
> 2) ChroMoly
> 3) Steel

Aluminium requires approx 4 times the material/diameter to be as
strong and stiff as a steel frame - hence equals bulky frame cf wilder

CroMo is a type of steel and is stronger than cds and erw steels - it
is the material of choice for the frames I make because I can make a
superstiff frame to my design out of it - ie a thin, light, non-bulky
frame.

be careful with cromo - if it is heated too much during the
brazing/welding process it will be severely compromised in strength -
also some grades eg 501 cannot be satisfactoraly welded at all and
must be brazed

> The other question I have is what sort of wall thickness and
diameter
> would you recommend for the forks and crown. The seat post stem is
> obviously a fixed internal diameter, but I am still curious on the
wall
> thickness.
>

If the wall is too thin the uni frame will break around the joints as
the tube will not have the local strength to resist the bending moment

> One last thing, I have machined bearing holders, they only have a
lip on
> one side, what is the general recommendation on the side that the
lip
> should be, inside (towards the wheel) or outside (towards the
cranks).

You REALLY want a lip on both sides of the holder to retain the
bearings properly - also the lip prevents the holder from deforming

> Any help is appreciated.

Hope that helps


Joe

Please visit pedal.me.uk for all your custom unicycle needs

Re: Question on Custom Frames

“Joe” <joe@pedal.me.uk> wrote in
news:mailman.1032127790.31700.rsu@unicycling.org:

>
>> I am going to get a custom frame made I was wondering what people
>> recommend as a good material to make them out of.
>
> Cool - Who is making it if you don’t mind me asking, if you don’t
> have a builder yet - email me

Judging by your email address you live in the UK, I live in Australia. I
am getting it made either by my Dad (a mechanic by trade) or a
specialised steel worker.

>
>> 1) Aluminium
>> 2) ChroMoly
>> 3) Steel
>
> Aluminium requires approx 4 times the material/diameter to be as
> strong and stiff as a steel frame - hence equals bulky frame cf wilder
>
> CroMo is a type of steel and is stronger than cds and erw steels - it
> is the material of choice for the frames I make because I can make a
> superstiff frame to my design out of it - ie a thin, light, non-bulky
> frame.
>
> be careful with cromo - if it is heated too much during the
> brazing/welding process it will be severely compromised in strength -
> also some grades eg 501 cannot be satisfactoraly welded at all and
> must be brazed
>
> > The other question I have is what sort of wall thickness and
> diameter
>> would you recommend for the forks and crown. The seat post stem is
>> obviously a fixed internal diameter, but I am still curious on the
> wall
>> thickness.
>>
>
>
> If the wall is too thin the uni frame will break around the joints as
> the tube will not have the local strength to resist the bending moment

Any recommendation on a suggested wall thickness for the different
materials?

>
>> One last thing, I have machined bearing holders, they only have a
> lip on
>> one side, what is the general recommendation on the side that the
> lip
>> should be, inside (towards the wheel) or outside (towards the
> cranks).
>
> You REALLY want a lip on both sides of the holder to retain the
> bearings properly - also the lip prevents the holder from deforming

The bearing holders are pretty chuncky, they are designed to fit a 40mm
OD bearing (6203) and the wall thickness is probably at least 10mm, I
don’t think that they will deform very easily.

>
>> Any help is appreciated.
>
> Hope that helps
>

Unix: It’s not just “User-Unfriendly”:
it’s ‘Proactively User-Hostile’!


Re: Question on Custom Frames

Put the lip on the outside (towards the cranks).
Both the KH and the Hunter have a lip on only one side of the bearing holders and the lip is on the outside. Both unicycle frames work just fine. As long as the bearing holder is beefy enough a single sided lip is not a problem. Another key is that the bearing holder needs to be round and fit the bearing snugly.

A lip on both sides that perfectly fits the width of the bearing would be better, but that is more difficult and more expensive to machine. DM’s bearing holders on the DMATU, Vortex and Ringmaster Advanced are made like this.

Re: Question on Custom Frames

Hey Jimmy,
Go for the ChroMo, your going to have better options for tubing. You don’t want the bulkiness you’ll get with aluminium, especially on a Coker frame.

For thicknessess you could talk to bicycle frame builders and find out what they’re using for building forks. You might want to try talking to Paul Wyganowski, He’s built a few Coker frames and a lot of other stuff.

My Profile MUni fork had one lip on the inside(twords the bearings)i never had any problems with that,i dont know which is really better. :thinking: one cool thing about the lip being on the inside on my Profile,is its flush with the bearing so you get to use those cool flying saucer spacers that Profile makes.