Home Made Bikes

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flag phutphutend
Posted: Feb 3, 2015 at 4:34 Quote
faul wrote:
Hi everyone!
This tread makes me want to make my own bike.
I started to draw an hardtail
Hardtail. 140mm fork Tubes everywhere to isolate vertical stiffness from lateral stiffness and keeping it strong. same geo as the dual suspension frame maximum tire clearance for muddy days made for fun if i make it some day.

But I wonders if a dual suspension frame if easier to make? It requires two smaller jigs, and if I don't makes the swingarm or the front triangle straight I can makes it again without making the whole bike. And now I have a lather, so I can make the axles and everything (I was searching a TIG welder but in the process someone made an offer I couldn't refuse. Big Grin The TIG welder will wait a little.)
140mm bike. it will be made out of steel single pivot without link or rocker to lower the weight and to keep things simple. It may have a floater brake. some chain pulley to isolate the suspension from drivetrain forces. 405mm chainstay longer when suspension move 420mm in sag position 64 head angle 420mm reach Not for children.

These drawingd aren't quite finished (I need to use tubes that already exist, to design a floater brake for the dual suspension, to change the bearing location and to modify some details).
Do anyone already see some drawback in the desingn?

These are the best CAD images I have seen! You have actually thought about how the frame is going to be built, rather than just drawing a some fancy curvy shape with millions of nonsense pivots!

But speaking of curvy shapes. Just stick to straight lines for your first bike (and probably the rest of them), bending large diameter pipes is a whole website in it's own right. Bending of small diameter stays however if pretty easy.
flag faul
Posted: Feb 3, 2015 at 12:00 Quote
Thank you for your answers.
BungedUP wrote:
It's not necessarily easier or harder - it's just different sets of problems. You can make either really hard to build or fairly easy. Whether they are worth the effort is another matter!

I'd suggest picking something based not off of whether it is easier or harder, but based off of what inspires you the most.
Ok, you gave me an excuse to focuse only on the dual suspension frame. It looks cooler so it will be the first.

phutphutend wrote:
These are the best CAD images I have seen! You have actually thought about how the frame is going to be built, rather than just drawing a some fancy curvy shape with millions of nonsense pivots!

But speaking of curvy shapes. Just stick to straight lines for your first bike (and probably the rest of them), bending large diameter pipes is a whole website in it's own right. Bending of small diameter stays however if pretty easy.
Thank you! Smile Yes I draw these bikes to be made, and because building is harder than drawing, I try to think at every details to help the building process. I don't have an easy acess to everything, so I can't draw something random and thin after how to make it.

For the curvy shapes, I know someone who can do that (if I find a tube with a good outer diameter). The tope tube will be curvy. I don't know yet for the downtube (I haven't found a downtube thick enough yet, so I don't know if I will be able to bend it. And it's useless here (I took it from a previous drawing of another frame)). And I think I can avoid it for the stays.
flag phutphutend
Posted: Feb 4, 2015 at 13:48 Quote
Tell me about hole saws...

All the ones I seem to use are crap. The teeth just snap off. Is any one brand better than any others? Am I cutting at too high a speed? Cutting high spec tunes is even worse.

Any help would be greatly appreciated.
flag jacque-lucque
Posted: Feb 4, 2015 at 14:22 Quote
I see a lot builders using Starrett hole saws. Plus they're yellow, so that's kind of neat.
flag Weldertron
Posted: Feb 4, 2015 at 15:05 Quote
Snapping teeth is usually a sign of to much pressure being applied. Burnt teeth are to high a turning speed.

What are you using for cutting lubricant?
flag BungedUP
O+
Posted: Feb 4, 2015 at 18:32 Quote
I've used just about everything, and there are ones that are better than others. Starrett 6-pitch are the best, really. Lenox are pretty decent as well. Using the correct SFM is good. Usually, a 1.25" holesaw does well at around 325 rpm and .007"/rev. Somewhere in that neighborhood is good. At 500 rpm, the holesaw life will go down.
flag BungedUP
O+
Posted: Feb 4, 2015 at 19:07 Quote
madm3chanic wrote:
rediculous, just stupendous...enter this bike into next years NAHBS, please! you stand a pretty good chance of winning bike of the show id say. lugged looking gussets/tigged frame with brazy bits...dang. Drool

whats goin on with the considerably larger diameter upper seat stay bit tho- it looks like there's a fair old gap between the tubes?

There's too many good builders for me to compete with at a place like that! I just plug along with what makes me happy. Someday I might get a booth at a small show, but I'm not doing too much different from a lot of other people, other than just having had a lot of production experience, and so maybe I'm a little more efficient, and know a few different tricks. There is a lot of cool stuff at those shows, I don't know if they need more of the same ol' from me. Thanks for the vote of confidence though - I do appreciate that.

Yeah, so those stays - I sleeved 5/8" tube into 3/4" x .035" tube. There is a bit of space, which is not equal all the way around the perimeter. When I roll the 5/8" tubing to get the long arc, I just use a 3/4" die, which ovalizes the tube. I made the bender, but haven't been motivated enough to make some new dies for other tube sizes (I made 3 different sizes initially). So on the sides, there's more gap than there is top and bottom. It's definitely not an ideal situation, where you'd have ~ .009" of gap for brass. In my case there'd be .028" of gap if the tube shape was uniform. Since it isn't, there's probably .035" or so of gap on each side. I've got enough meat in the sleeve (ugh that was terrible phrasing) that it should be ok. I sucked a lot of brass down into the joint, and I've done this sort of "air-brazing" on triples, quads, and quintuple bikes, where it held up pretty well. That was for attaching seatstays to dropouts when I worked at Co-Motion. I eventually realized we could use fork tip plugs that we had on hand to get rid of the giant gaps that needed to brazed. It doesn't look like Rene Herse stuff to be sure, but it'll work for me! Good call, by the way.
flag madm3chanic
Posted: Feb 4, 2015 at 20:44 Quote
you could maybe snip the 3/4" tube on one side of the tube only, after bending (keep that side downwards on installation for subtlety), smoosh it closed with a clamp, tig it up and grind it smooth...you'd easily be able to pinch it that much and no-one would ever know...

seems a shame on a bike that fine and invest that many hours to have one little detail like that bringing it down a bit.
flag BungedUP
O+
Posted: Feb 4, 2015 at 21:07 Quote
madm3chanic wrote:
you could maybe snip the 3/4" tube on one side of the tube only, after bending (keep that side downwards on installation for subtlety), smoosh it closed with a clamp, tig it up and grind it smooth...you'd easily be able to pinch it that much and no-one would ever know...

seems a shame on a bike that fine and invest that many hours to have one little detail like that bringing it down a bit.

You're thinking basically give the 3/4" tube a little taper? That's an interesting thought. I did try to figure out a reasonable way to flare the smaller tube, and make it larger. I gave it a few attempts on a rigid mandrel, but then soon realized I either needed a lot more pressure, or an expanding mandrel (with a lot of pressure). Or a mandrel that would stay stable at temperatures where the steel would be more fluid and hot work it. I like your idea though, and might give it a try on a subsequent frame.

More detail of what seatstay joint looks like:
Detail of seat stays

Another option would be to do the stays serially - meaning, make an intermediate sleeve section. I thought that would look odd in this case, though. The goal was to be able to use 3/4" up top for good proportionality, and then something smaller towards the dropout as the chainstays tapered down as well. It visually accomplished what I wanted, and I'm pretty happy with it overall. I can understand how some would prefer the theoretically superior better fitting, and thinner border between the tubes, but I'll be quite satisfied, personally. Future improvement, and ideas contributing to that though are welcome.
flag madm3chanic
Posted: Feb 4, 2015 at 21:19 Quote
BungedUP wrote:
madm3chanic wrote:
you could maybe snip the 3/4" tube on one side of the tube only, after bending (keep that side downwards on installation for subtlety), smoosh it closed with a clamp, tig it up and grind it smooth...you'd easily be able to pinch it that much and no-one would ever know...

seems a shame on a bike that fine and invest that many hours to have one little detail like that bringing it down a bit.

You're thinking basically give the 3/4" tube a little taper? That's an interesting thought. I did try to figure out a reasonable way to flare the smaller tube, and make it larger. I gave it a few attempts on a rigid mandrel, but then soon realized I either needed a lot more pressure, or an expanding mandrel (with a lot of pressure). Or a mandrel that would stay stable at temperatures where the steel would be more fluid and hot work it. I like your idea though, and might give it a try on a subsequent frame.

Another option would be to do the stays serially - meaning, make an intermediate sleeve section. I thought that would look odd in this case, though. The goal was to be able to use 3/4" up top for good proportionality, and then something smaller towards the dropout as the chainstays tapered down as well. It visually accomplished what I wanted, and I'm pretty happy with it overall. I can understand how some would prefer the theoretically superior better fitting, and thinner border between the tubes, but I'll be quite satisfied, personally. Future improvement, and ideas contributing to that though are welcome.

yep i actually started writing my response about making the 5/8" larger by cutting it, jamming a taper into it and plugging the gap with weld but realised while writing that it'd be a shit-ton easier making the larger tube smaller...great minds and all that.
flag BungedUP
O+
Posted: Feb 4, 2015 at 21:37 Quote
madm3chanic wrote:

yep i actually started writing my response about making the 5/8" larger by cutting it, jamming a taper into it and plugging the gap with weld but realised while writing that it'd be a shit-ton easier making the larger tube smaller...great minds and all that.

You know, that just gave me another idea - another option would be to turn a tapered sleeve for the 5/8" stock, where it tapers up to .662" OD, and stays even for an inch or so (where it inserts into the 3/4" tube), and then tapers into the 5/8 stock. The trick would be brazing the sleeve on first, then roll bending the tube, then brazing to the larger tube without melting out the first sleeved joint. I suppose welding the upper end, then plug welding the tube to the sleeve, then brazing both simultaneously might work too. The only advantage would be to maintain the contact where the 2 tube sleeve together, as opposed to a tapered to straight tube interface. I might not be making any sense - It's hard to describe. I'm not sure it's really any better either! Just another thought that popped into my head.

I actually also like the expansion idea you have there- I think that method for flaring might be easier to hide than trying to swedge the larger tube down.
flag BungedUP
O+
Posted: Feb 4, 2015 at 21:43 Quote
ORRR... Maybe a tapered seatstay (commerically available ones) could be roll bent? It would definitely progressively distort, but maybe the taper is gradual enough that it could be done in stages, such that it would not distort enough to matter? Hmmm.
flag BungedUP
O+
Posted: Feb 4, 2015 at 21:46 Quote
ORRRRRRRR I could make a bender similar to a fork raker, which might work too.
flag madm3chanic
Posted: Feb 4, 2015 at 21:48 Quote
i recon the turned plug option may look aesthetically a bit strange- a "sudden" taper on the end of a tube like that could look a bit weird. it'd be hard to know without trying it tho (or maybe cad it?)

or to make things a little less complicated, why not just use a set of straight, single taper seatstays like this-

http://www.cycle-frames.com/bicycle-frame-tubing/NOVA-CRMO-19mm-x-0.8-SINGLE-TAPER-600.html

they are always stupid long, you could just cut the fat end off at the point where the taper would jam into your 3/4" tube and bend/fit it before the braze.

*edit*- you mentioned it litterally while i was writing it. yes you just bend em the same way as your normal tube, the taper is so gradual that it doesnt matter a damn
flag madm3chanic
Posted: Feb 4, 2015 at 21:51 Quote
on a completely unrelated topic, i just got a set of 1.2" slicks for my trail bike that i posted last week...im turning to the dark side!
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...next ill be buying lycra Confused

 


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