making a frame?

[chasebro]

hey guys i am loooking into building my own frame. and yes i have all of the stuff i will need i.e. laser cutter, tig wealder 100 tonne press any thing i could possibly need. i am looking to make it out of just round cromolly or is there something better? well if anyone has any designs can they send them trough to me or any geometry just to work off.
oh btw i want a street/dirt jump hardtial

cheers,

 

[hardtailer]

go withg something along the lines of:
Head Tube Angle: 71

Seat Angle: 70

Top Tube Length: 614.5

Chainstay Length: 430.0

this is the geo of my bike
and its great, ohh but i would shorten the chainstay, hope that helps a little

 

[hardinge915]

hey guys i am loooking into building my own frame. and yes i have all of the stuff i will need i.e. laser cutter, tig wealder 100 tonne press any thing i could possibly need. i am looking to make it out of just round cromolly or is there something better? well if anyone has any designs can they send them trough to me or any geometry just to work off.
oh btw i want a street/dirt jump hardtial

cheers,

mate, its ALOT of work to build your own frame. Do you have a milling machine to machine the ends of your pipes to ensure its a perfect fit so its easy to weld? And if you want to be different, make the frame out of stainless tube, I dont no how it would hold up under riding abuse but heck, will look awsome if you put a clear gloss on it and put it on you wall

 

[---Matt---]

Hey,

Firstly, CR-MO is probably the best to build with if you're not confident with building as it's easier to manipulate and weld if you're not experienced. It also doesn't require heat treating. However, CR-MO tubing is fairly expensive to start with. You're looking at approx $7.00 per foot length I believe and you'll need different lengths of different sizes and thicknesses. I'm using 1 1/2", 1 1/4" and 3/4" OD plus the seat tube size (can't remember what tube we got for that at the moment) as well as CR-MO plate for the dropouts and gussets if you have any. You'll also find a lot of places have a minimum order of $100 or more as they normally deal with larger companies and $100 minimum order makes it worth their while although if you buy enough for two frames, you'll easily spend over $100. Building a frame is by no means, a cheap way out and it will probably turn into a very extended project.

As for geometry, you're going to get a lot of conflicting views of what is considered "RIGHT" for you. I'm currently in the process of building a bike myself and what I've done is take all the frames that I've ridden and tried to determine what I did and didn't like in terms of geometry. From that I came to the conclusion that I wanted a bike with around 16.5" chainstays, vertical dropouts with disc mounts & 135mm QR rear end, approx 70 degree headangle and about a 73 degree seat angle with a 22.5" top tube. However, this all depends on what YOU like in a bike. Also be aware that what you design on paper may not be exactly what you end up building as the slightest mistake in building can change angles by a lot. This is my first bike build and I am sure there will be a lot I want to change and it is all a VERY BIG learning experience. I'm sure that in the future the bikes I design/build will be a lot closer to the mark.

hope that helps.... even a little.

Cheers,
---Matt---

 

[---Matt---]

mate, its ALOT of work to build your own frame. Do you have a milling machine to machine the ends of your pipes to ensure its a perfect fit so its easy to weld? And if you want to be different, make the frame out of stainless tube, I dont no how it would hold up under riding abuse but heck, will look awsome if you put a clear gloss on it and put it on you wall

You have got to be kidding! Not only would stainless steel be EXTREMELY heavy, it would also be waaaay expensive, hard to machine, very hard to weld and would probably crack very soon after building.

Also, you don't necessarily need a milling machine. I've done my frame so far with a hack saw and a file. So it is possible, it just takes a bit of time and patience to get it right.

---Matt---

 

[porky]

make it outof aluminium.

 

[Jimmy401]

make it outof aluminium.

alluminium welding is extremely difficult and only rarely holds if it is an ametur doing it. If you can do it, my hat goes off to you, and as they say you could weld a banana to glass. but yer i would go with cromo, easy to weld and very solid, make sure you treat the welds soon after they are done or they will rust really badly.

 

[hardinge915]

You have got to be kidding! Not only would stainless steel be EXTREMELY heavy, it would also be waaaay expensive, hard to machine, very hard to weld and would probably crack very soon after building.

Also, you don't necessarily need a milling machine. I've done my frame so far with a hack saw and a file. So it is possible, it just takes a bit of time and patience to get it right.

---Matt---

I get my stainless tube alot cheaper than you would expect to pay, i get my mates offcuts etc from his sheet metal buissiness and most of his offcuts are more than 1m in length so i get them cheap. Heavy, yes but hard to weld, i dont think so, and its not all that hard to machine, remember your milling tube, not 6mm plate.

As for needing a milling machine, yes your right you dont need one, but it makes your job alot quicker and in some points 'cleaner'. At tafe we were griding, hacksawing and filing aluminium pipe to fit another pipe and weld as if it was our headtube, toptube and downtube. Very long process.

 

[chasebro]

mate, its ALOT of work to build your own frame. Do you have a milling machine to machine the ends of your pipes to ensure its a perfect fit so its easy to weld? And if you want to be different, make the frame out of stainless tube, I dont no how it would hold up under riding abuse but heck, will look awsome if you put a clear gloss on it and put it on you wall

yeh i got all of the stuff you could possibly need
milling machine

 

[---Matt---]

I get my stainless tube alot cheaper than you would expect to pay, i get my mates offcuts etc from his sheet metal buissiness and most of his offcuts are more than 1m in length so i get them cheap. Heavy, yes but hard to weld, i dont think so, and its not all that hard to machine, remember your milling tube, not 6mm plate.

As for needing a milling machine, yes your right you dont need one, but it makes your job alot quicker and in some points 'cleaner'. At tafe we were griding, hacksawing and filing aluminium pipe to fit another pipe and weld as if it was our headtube, toptube and downtube. Very long process.

Fair enough with the machining tubing but he will still need to make the dropouts and gussets which would be made of plate and would be hard to cut. Stainless is still going to be more likely to crack than standard cr-mo so I guess what I'm saying is that if he's going to build a bike that he wants to ride, let alone jump, he'll need to stick what's considered to be the best materials. There's a reason CR-MO is used and Stainless isn't.

---Matt---

 

[scottmeister]

Keeping in mind generalising about the weldability and overall strength of cromoly and stainless steel is useless without specifying grades. Stainless can be hard to weld, but it completely depends on the percentage chromium, nickel etc content of the alloy.

Any 4130 cromoly should be heated prior to welding. kthx.

 

[miko]

Do it out of Chromoly. Preferably get a nice tube set, like reynolds etc.

Some tube sets and resources can be found at henryjames.com.

As far as geo goes, I'd spend a bit of time digging around bike manufacturers websites. Fine bikes that are built for what you want to do, and just rip off their geometry. You'll have enough work to do without re-inventing the wheel. If you can possibly score a test ride on some of the bikes, through mates or a shop, that would be even better. Then you can determine that that geo does what you want.

Good luck!

 

[phillearned]

You should Check out this thread:

http://forums.farkin.net/showthread.php?t=35194

From experience, the main thing that will make it easier to "whip up" a frame is a frame building jig. The one i had access to for building my frame was close to $10,000 to buy (it wasnt mine).... you can build something that will do the job for a lot less though. The jig basically has to hold the seat tube, bottom bracket and head tube at the correct angles and distances apart, while the other tubes are welded in place. Then there are other smaller jigs and alignment tools that hold the dropouts and various other bits that are necesary in place too.
If you have any questons, drop us a PM.

 

[look i can faceplant]

hey im building/designing a dj/street hardtail for a design and technology project

i started out by searching what people liked in this sort of bike and what the most popular bikes out there were. i found all the different bikes geometry and tweaked bits here and there and added bits from another bike i liked and so on. i did this until i was happy with my final design.(by the way for the design i used bike cad there is a free deom online which isnt bad google the words bike cad and its the bike forest website)

the next step was to design and build a jig for the frame out of plywood and metal bracing and vices.

i cant help out on the welding side of things as i am getting the welds all professionally done for rather cheap

well i hope this was of some help oh and by the way its a cromo frame

 

[::RideSiK::]

can i ask anyones history in welding that have replied to this thread?

im doing a pre app now and some stuff thats been said i woudlnt aggree with but im not sure if thats my lack of knowledge or not...

 

[hardinge915]

can i ask anyones history in welding that have replied to this thread?

im doing a pre app now and some stuff thats been said i woudlnt aggree with but im not sure if thats my lack of knowledge or not...

I do welding and thermal cutting at tafe for the last year and a bit... i dont no grades or anything like that, i just weld the stuff.

 

[Grip]

Any 4130 cromoly should be heated prior to welding. kthx.

Scott, 4130 tubing of the thickness used for frame building would never need preheating.

 

[chasebro]

Do it out of Chromoly. Preferably get a nice tube set, like reynolds etc.

Some tube sets and resources can be found at henryjames.com.

Good luck!

that site is so helpful thanks alot for everyones help

 

[hardtail free rider]

i have built my own ht frame, more of a prototype. yes it is a huge learning curve, and you'd be surpirsed what you can build with an arc welder, drill press angle grinder and a hack saw....

any way as far as geo goes....HA you can fcuk off all the bike websites....all that matters is trig...yeh that right the shit they tried to teach you in spesh maths comes back to bite you in the ass!

just because you have a head angle, top tube length, and seat angle, doesnt give you the other lengths, or angles? ..... or does it?



i've been dan cran

 

[MUGEN]

i have built my own ht frame, more of a prototype. yes it is a huge learning curve, and you'd be surpirsed what you can build with an arc welder, drill press angle grinder and a hack saw....

any way as far as geo goes....HA you can fcuk off all the bike websites....all that matters is trig...yeh that right the shit they tried to teach you in spesh maths comes back to bite you in the ass!

just because you have a head angle, top tube length, and seat angle, doesnt give you the other lengths, or angles? ..... or does it?



i've been dan cran

A sound understanding of trig is needed to build a frame up from scratch, but u dont need to do that.
Just get a frame, make a template/jig out of it, and fine tune the geo to your liking.