Frame Building 101

[---Matt---]

UPDATE: Just finished another frame - See post #107

Hey everyone,

It seems that every time we (Benj and myself) post up a new frame we get the same questions regarding the design/construction process so, now that I'm about to build another frame I thought I'd post this up.

Firstly I'd like to say that this is by no means the only way you can build frames, however it is the way that has worked for us.
Now this will be a step by step list as I go through building this frame. Hopefully this way I won't miss anything.
For this part of the process you'll need a PC and a lot of time/patience to think about the frame and nut everything out.

To start off I figure out exactly what kind of bike I want. The bike I'm working on currently is going to be a 4x hard tail, so I figured I want, being 6'2", the following geometry:

- 70 deg head angle
- 71 deg seat angle
- 390mm CP length (Cockpit Length = horizontal distance between the BB shell and the top of the head tube)
- 12.7mm BB drop
- 419.1mm chain stays
- 370mm seat tube

You also need to determine other things such as:
- Dropouts: 10x135mm vertical, 10x135mm horizontal, 12x135mm bolt through or 12x150mm bolt through (I like 10x135mm vertical because I'm different)
- Head tube length - 115mm for this bike
- Disc mounts or not

Also needed is some basic MTB standards such as tyre width, chain ring spacing, chain ring diameters, ISCG standards, disc mount standards, crown width and drop and axle to crown height of the forks you're going to be using.
Also take note of the size of the headset you're going to use and take this into account when you draw it up as this will affect the head angle. You should also take care with making sure that the smallest gear on the rear cassette has clearance for the chain past the seat stays

Now that's done, draw a 2D base sketch up in whatever CAD software you prefer to use. I use Solidworks because it is fairly easy to learn and use however it is licensed software and therefore it costs money to buy.

Once you get all the parts down onto the screen it should look something like this. (Click on the pics for bigger versions)


Then you get to work making it into a 3D model. This takes time to get right so be patient. I'm not going to go into how to use Solidworks so if you're not sure then hop onto Google and look it up

Now that all the parts are in the design, including chain ring spacing and tyre size, etc. you should get something like this: (Click on the pics for bigger versions)







Just a tip, make sure you label every sketch and extrusion as it will make it much easier to go back and modify the design if needed.

Once you get all this done and are happy with how it looks you're ready to get outside and get your hands dirty. I'll get more into that next time.

---Matt---

 

[Grip]

This is going to be a great thread, thanks Matt. Think I'll sticky it now

 

[Bowlo]

Sweet work Matt!!
Bowlo

 

[Chikn32]

Hah - You've got me thinking, ...*if he can do that, why can't I*

Prolly because I can't weld.

If we did up a design like that, are there companies out there that would weld it all up for us?

What kind of price would they be asking? I know it would depend a lot on the material used, but what would a ballpark figure be?

Cheers,
Nick

 

[Chikn32]

After a bit more thought...

My welding skills are non-existant, so if I want to make up a nice bike, I may as well farm it out to someone who specializes in it all. Draw up a design, give them the specs and standards, and let them at it. What then is stopping me from copying something like the Appalache Real frame? I know I'll never own one, but if I were to just copy the design of one, it'd be kinda like riding a carbon copy... I'm an engineering student and at uni I've got access to pretty much any design software, so I think if i could get my hands on a frame, I could make a pretty accurate design.

I know the point is to ride something that is your own creation, but the Real looks like a damn good ride...


Lol, look out for me in prison after violating Appalache copyright

 

[dazz]

What then is stopping me from copying something like the Appalache Real frame?

1 - copyright.
2 - cost, the Real has a hell of a lot of machining gone into it, to get all that done as a one off, buy the specialty tubing & then pay someone with the skills required to weld it up correctly, then find somewhere that can perform the heat treatment required on such a lightweight frame.

If you took the basic design & modified & beefed it up using CroMo tubing & steel plates throughout, I can't see any reason why it couldn't be built for a reasonable price. It'll weigh twice as much as a Real & wont really look the same, but yeah that could be done.

Infact I've already got a design you can use if you like (drawn in AutoCAD) which is based on an Apalache. I'll deny everything if it fails & someone gets hurt though.

 

[Chikn32]

Hah, for real?!

Could you pass it onto chikn32@hotmail.com...I'd be interested in having a look

 

[t]

I like that half yolk at the seat stay/seat tube junction... did that come from where I think it did?

 

[---Matt---]

I like that half yolk at the seat stay/seat tube junction... did that come from where I think it did?

Maybe Nothing wrong with a little inspiration! I think that area's different enough that I'd like to call it my own


Oh, and to Chikn32, why bother copying someone elses design to a tee. If you're going to do that, just bite the bullet and lay down the cash. They will almost certainly do a better job, with a lighter weight and stronger frame. Look closely at the amount of machining that has gone into that frame and the BB7, even just around where the shock mounts near the BB shell. Unless you have access to a mill and can weld aluminium very well it's just not going to work.

I think if you're going to make a frame, make it for yourself to your specifications and have fun knowing that it's your design and you thought of it, not somebody else that you copied.

---Matt---

 

[Plow King]

Nice one matt

Welcome to the sticky club..

Wait, wait... That didn't sound good at all.

 

[---Matt---]

Part 2

Hey again,

I've progressed a fair bit in the last couple days so I'll try and fit as much in here as I can.

To start with, I should say that the majority of time wasting in this part is due to the jigging of the parts, making sure they're lined up accurately and snug. The last thing you want is to have your back wheel in crooked when you're riding along... I learnt that on my first frame

The first thing I usually do is draw out the base sketch on a piece of painted MDF. This is the main jig we use to build the frame. Make sure you take care with all the sketches you draw out because one little mistake can change your head angle from the desired 70 degrees to 72 degrees with a very slight mistake of the protractor.



Then I turn up the headtube and sit it in the right spot and make sure it's the right length. We use 1.5"*.083" tubing for the headtube and it needs a slight bit of machining to allow the headset to fit properly.



After this we need to sketch out the back end onto two separate boards. One we use to slot the chainstays so we can weld the dropouts in and the other we use to tack and weld the back end together. At this point also mark in things like chainring, tyre and crank clearance.

Chainstay Sketch - For tacking


Chainstay Sketch - For slotting


Once these are drawn out I cut out the dropouts and file them into shape. In this part make sure you have nice sharp drill bits and punch the steel before you drill it as this will help keep the drill in the correct spot. For example, if you have the drill off by 1mm on the disc mounts, the mount won't fit.
Once cut out and filed, my dropouts look like this.



Now that the dropouts are done I started work on the chainstay yoke. To do this I cut the rough shape of the yoke and filed to shape. Then mark lines approximately 10mm apart perpendicular to the length of the yoke, put the yoke in the vice and hit it with a hammer. This might sound crude but it does get a roughly enough round shape and will give a good result.
The yoke should look something like this when done.



Next we make the wishbone. For this bike I used a 1.5" tube and squashed it in the vice down to an oval 1.25" shape. This should hopefully give the bike less lateral flex. Once squashed, file it to shape by fitting it against the BB shell and the chainstay yoke; making sure it fits flush with both surfaces and is not twisted.





Now it's time to make the chainstays. First you need to bend the tubes. To do this you need a tube bender; here's one that we made. It's worked well for a few bikes but, being wood, is starting to wear out. I'm sure you could have the tube bent for you somewhere like a muffler place however we like to do as much as we can here.





Once the tubes are bent, cut them to length and slot them. Basically it's just an angle grinder in a jig. At this stage you should have already drawn out the back end onto the board that you're using to slot the tubes with. Here's a picture of the tube slotter we set up.









Once slotted, file out the tube so that the dropouts are a tight fit into the tubes. Make sure that when you slot the tubes you slot them to an even depth and at the right angle. It should all fit together smoothly if you have everything jigged up correctly.

Now it's time to start welding. First, we weld the BB shell to the wishbone and the yoke. Make sure that before you weld any parts of the frame that you have holes drilled in the different parts as the gas will need to escape somewhere when you weld.
Once you have welded the front end together you need to file the chainstays off at the right angle so they fit flush with the chainstay yoke. This takes patience so just take your time and make sure you don't go too far. Once you've done that it'll all fit together nicely and you'll be ready to finish welding.

Tack the parts together first and then once it's together you can take it out of the jig and weld the rest of it. Make sure you tack it carefully as when you tack the tubes they can twist if there isn't an even force on all sides.








PHEW!

---Matt---

 

[Giantrider]

perfect!!! i was sitting in dt today learning about c.a.d. wanting to try and draw a frame on c.a.d and now i've found the perfect thread
thanx heaps matt...

Hamish

 

[dazz]

Hey Chikn32, I've sent you my AutoCAD sketchings, have a look & let me know what you think.

Matt, looks like your latest frame is coming along great! You're proving to be worthy of the 'Sticky Club'. Man! That does sound bad...

 

[miko]

Damn Matt, stop making it look so easy, you're taking away my excuses.

 

[Fraz]

Thats Awesome!!! This thread has really giving me the inspiration to try it myself. Even though at the moment i cant weld or anything its always been something i have wanted to try. Dont forget to keep us updated with the work on the rest of the frame...

So, when you build your frame, Do you have to base the frame around a set of forks you intend on putting on it, so you get the right Head Angle?

Now that Im thinking about it theres a whole lot of stuff you have got to consider when building a frame sounds tricky.

 

[Jon]

Matt that looks awesome ,seriously tempted to have a go.Do you have any problems with welding heat ruining the temper of the tube or do you re-temper after welding ?Also is the tube 4130 and if so would metal sales places have it or be able to get it? Damn that looks like fun,top job!
cheers jon

 

[---Matt---]

So, when you build your frame, Do you have to base the frame around a set of forks you intend on putting on it, so you get the right Head Angle?

Now that I'm thinking about it theres a whole lot of stuff you have got to consider when building a frame sounds tricky.

Yep, there's a lot of stuff to consider! It takes a lot of time and effort to put together everything you need, even before starting to buy tubing! Luckily Benj has been awesome in organising, designing and making the jigging and was able to get 99% of what we needed together while at TAFE.
Although, we've hit a stumbling block on this frame at the moment with bending the thinner tube we're using. The tube bender we made is excellent for bending 0.049" tubing but the seat stays on this bike are 0.035". We're working on a solution though. Not sure if we'll have it any time soon though. As soon as we do, it'll be posted here!

Matt that looks awesome ,seriously tempted to have a go.Do you have any problems with welding heat ruining the temper of the tube or do you re-temper after welding ?Also is the tube 4130 and if so would metal sales places have it or be able to get it? Damn that looks like fun,top job!
cheers jon

Thanks Jon! So far so good as far as tubing is concerned and I guess I should have mentioned that we only use 4130 T-6 CrMo. Being a fully backyard operation, we don't have the resources to heat treat the metal after welding. On the original frame we made back in August last year we used ER70s-2 welding filler rods and, as far as I'm aware, they don't need the heat treating. Grip is the man to ask about that though!

As for tubing, we get it from different places and no, a standard steel retailer won't sell it or have ANY CLUE where to get it. As we're in Melbourne we try to get all the tubing locally and hence not have to pay for freight. Therefore the majority of tubing we get from Airport Metals and just recently we found a semi-local place, FabRaiCations that sells the 1.5"x0.035" tubing that I'm using for this frame and haven't been able to find anywhere else. We get the BB shells from either British International in Sydney (cheaper but adds shipping) or Greenspeed Recumbents in Melbourne.

---Matt---

 

[Grip]

I just saw Matt's first frame yesterday (Wayne's bike... that one with the looping seat stays) and I'm mighty impressed. Bloody good work there, guys and I can't wait to see this project you're into now too.

As for the welding rods and heat treatment (Jon asked about it)... as Matt says, the ER70s-2 filler rods are basically a "mild steel" rod and because of the resultant and superior ductility those have over a "proper" CrMo filler rod, heat treatment isn't needed, useful or even recommended (as in the case of a filler rod that actually matches the composition of the tubing being used).

And by the way, the issue of heat treating frames is a bit misleading. The whole idea really is to use heatreated/tempered tube and then design joints and use welding rods and techniques that allow for and work with the heat affected zone created by the welding process. Actually heat treating an entire frame after it's built would be a nightmare... you'd need a jig the size of a fridge and solid as a rock built around the frame and pulling/holding it in every direction so you didn't end up with something that looked like a week-old bowl of spag.

 

[---Matt---]

I just saw Matt's first frame yesterday (Wayne's bike... that one with the looping seat stays)...

2nd frame... But who's counting?

---Matt---

 

[---Matt---]

So on to part 3...

This section will be pretty short but has lots of pics.

Since last post I have filed out the tubing for the front end and started work on the seat stays. I've also made the gusset for the headtube and will soon start working on the ISCG tab too.

So to start with we mounted the headtube and chainstay on the main jig. Once this was done we made the down tube. We do all our mitering using a hacksaw and file and have a very handy program, aptly named "Tubemiter". This is a tiny program that lets you enter the diameter, thickness and angle of the tube you're mitering and size of the tube you're mitering to and print out in life size the shape you should be cutting to. You can find this program here: http://www.ihpva.org/people/tstrike/tubemiter.exe

When you've entered the details and printed it out it looks like this:


When it's wrapped around the tube and filed to shape you get this:


Once the downtube is filed out we welded it into place. Once done it looks like this:



Then we filed the seat tube and top tube and end up with this:




Next we started work on the head tube gusset. This is easier to make than it looks. Just using a piece of tube the same size as the down tube cut it down the middle, separate it and then cut into shape.
Make sure when fitting it to the bike it fits snugly on all edges.









Next we started work on the seat stays. This was a challenge because we're using thinner tubing than ever before and hence we had issues bending the tube properly. To get around this we modified our bender to add a mandrel. This allowed us to keep the shape of the tube as it's bent. it didn't work perfectly however it gave us a good enough result to use.





Trial and error!!!


The final result


And for the moment my frame looks like this:







NEARLY THERE!

---Matt---