Computer Program to calculate frame dimensions?

(Pete Cresswell) said:

I've got a new harttail MTB frame that didn't work out so well...in fact the builder offered to
build another one just for the cost of tubing and other parts to get it off the road (it has his
name on it...).

I've been riding it and have my adjusted my position to where it's tolerable but the problem I'm
having measurement-wise is that when one thing changes, other things tend to change in unexpected
ways. I'm afraid to say "just change

Quoted message said:

else.

I've got another frame (FS) that's pretty much dialed in - but on which I've got to use a 2"
setback seatpost to get myself to KOPS.

Seems like I should be able to measure all the dimensions on that frame, key them into a computer
program, then try altering this or that dimension and have the program show me what else changes
and by how much....or even tell the program to constrain certain dimensions....

Anybody know of something in this line?
-----------------------
PeteCresswell

actualy frames have been built for so long that Nothing changes 'unexpectedly" for an
*experienced* builder. my suggestion is you get a true frame builder to do the work not just some
hack with a torch.

RE/

Quoted message said:

actualy frames have been built for so long that Nothing changes 'unexpectedly" for an
*experienced* builder. my suggestion is you get a true frame builder to do the work not just some
hack with a torch.

I have no doubt that just about any builder is in full control as long as nobody's telling him
what to do.

The doubts I have grow around the builder's idea of what a proper fit is for me.

The guy who did the first one is no hack - he's survived for over 20 years building frames and
nothing else.

I think two things were wrong. First, I tried to tell him too much and he followed my flawed
instructions - rather than arguing with some lunatic that outweighs him by a factor of at least two,
maybe three... Second, I don't think he's got a lot of experience with MTBs. (i.e. he didn't think
about fork clearance in terms of those little adjustment knobs on the crown...)

I've since tried to establish contact with a guy on the West Coast that makes a single-speed frame
that others have given good reviews to. Racked up about a half hour of cell phone time after which
he asked me to write an email.....Never got a reply...

I *may* be back to just buying an off-the-shelf steel frame and having the S&S couplings
retrofitted. Sure would be a lot cheaper.

The two primary uses for this bike are:
- To have a bike that I can store in my vehicle's rooftop box or in the trunk of a small-ish car
and just sort of forget about until an unexpected riding opportunity arises
- To function as a spare while the FS is offline for repair.

But I need about two additional inches of setback to get KOPS on my FS and, I'm guessing, on any
other off-the-shelf frame. That puts me back far enough to make the front end really light. Not a
problem until you get to those grades where you're shifting weight back-and-forth balancing the
tradeoff between the front wheel floating and the rear breaking traction - or where you're trying to
zig-zag up a hill pedalling hard and the thing comes unglued just as you're laying into a turn.

The "frame-gone-bad" that I'm riding now corrects that floaty front wheel and I think I like
it....whether I like it enough to go through the process of another custom frame remains to
be seen...
-----------------------
PeteCresswell

(Pete Cresswell) said:

I've got a new harttail MTB frame that didn't work out so well...in fact the builder offered to
build another one just for the cost of tubing and other parts to get it off the road (it has his
name on it...).

I've been riding it and have my adjusted my position to where it's tolerable but the problem I'm
having measurement-wise is that when one thing changes, other things tend to change in unexpected
ways. I'm afraid to say "just change

Quoted message said:

else.

I've got another frame (FS) that's pretty much dialed in - but on which I've got to use a 2"
setback seatpost to get myself to KOPS.

Seems like I should be able to measure all the dimensions on that frame, key them into a computer
program, then try altering this or that dimension and have the program show me what else changes
and by how much....or even tell the program to constrain certain dimensions....

Anybody know of something in this line?

Not online, but if you have a frame that's dialed in fit-wise, it's not too hard to convert the
measurements to a new design.

For example, if you can measure the relationship between the BB, the saddle and the bars, you can
"draw a bike around those points". Here's where experience comes in - it's nice to know the effects
of the different ways of making the bike fit those three points. For example, radically shortening
the top tube might help get the cockpit length right, but you have to know how it will affect toe
overlap with the front wheel, and handling, and weight distribution, etc.

FWIW, when I'm designing custom frames for people with a frame that fits, I use a CAD program to lay
down the three points, then draw the rest of the bike around them. I'm not aware of any online tool
to do the same, but any CAD program (or even engineering graph paper) will suffice.

Mark Hickey Habanero Cycles habcycles.comhabcycles.comOpen ↗ Home of the $695 ti frame

"(Pete Cresswell)" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

I've got a new harttail MTB frame that didn't work out so well...in fact

the

Quoted message said:

builder offered to build another one just for the cost of tubing and other

parts

Quoted message said:

to get it off the road (it has his name on it...).

I've been riding it and have my adjusted my position to where it's

tolerable but

Quoted message said:

the problem I'm having measurement-wise is that when one thing changes,

other

Quoted message said:

things tend to change in unexpected ways. I'm afraid to say "just change

something

Quoted message said:

else.

I've got another frame (FS) that's pretty much dialed in - but on which

I've got

Quoted message said:

to use a 2" setback seatpost to get myself to KOPS.

Seems like I should be able to measure all the dimensions on that frame,

key

Quoted message said:

them into a computer program, then try altering this or that dimension and

have

Quoted message said:

the program show me what else changes and by how much....or even tell the program to constrain
certain dimensions....

I do not but it is not at all difficult or time consuming to draw a bicycle frame. Perhaps you might
do a few drawings with relevant items at various values and compare the results?

--
Andrew Muzi yellowjersey.orgyellowjersey.orgOpen ↗ Open every day since 1 April 1971

I have one that I made while agonizing over my newest road bike, I'll put it here:

www.hollasch.com/bike_geometry.xls

It is by no means a polished piece of work, nor do I guarantee its accuracy. Nonetheless, it is
quite exhaustive, allowing you to input pretty much any dimension and angle you could think of on a
bike, and it outputs the relative position between the handlebars and seat (the original reason I
made it), as well as standover height, saddle setback, wheelbase, front-center, and trail. Its based
on an X,Y coordinate system that is 0,0 at the point on the ground directly below the bottom
bracket, and uses a whole lot of high school geometry (I think if my high school geometry teacher
saw this he would cry).

Note that there are roll-over notes on many of the cells which explain what they are.

Have fun and let me know what you think.

Kyle

"A Muzi" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

"(Pete Cresswell)" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

I've got a new harttail MTB frame that didn't work out so well...in fact

the

Quoted message said:

builder offered to build another one just for the cost of tubing and

other

Quoted message said:

parts

Quoted message said:

to get it off the road (it has his name on it...).

I've been riding it and have my adjusted my position to where it's

tolerable but

Quoted message said:

the problem I'm having measurement-wise is that when one thing changes,

other

Quoted message said:

things tend to change in unexpected ways. I'm afraid to say "just

change

Quoted message said:

something

Quoted message said:

else.

I've got another frame (FS) that's pretty much dialed in - but on which

I've got

Quoted message said:

to use a 2" setback seatpost to get myself to KOPS.

Seems like I should be able to measure all the dimensions on that frame,

key

Quoted message said:

them into a computer program, then try altering this or that dimension

and

Quoted message said:

have

Quoted message said:

the program show me what else changes and by how much....or even tell

the

Quoted message said:

Quoted message said:

program to constrain certain dimensions....

I do not but it is not at all difficult or time consuming to draw a

bicycle

Quoted message said:

frame. Perhaps you might do a few drawings with relevant items at various values and compare the
results?

--
Andrew Muzi yellowjersey.orgyellowjersey.orgOpen ↗ Open every day since 1 April 1971