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flag ricar
Posted: May 14, 2014 at 5:42 Quote
I have yet to see a frame building thread based on this style of bike. I am really interested in building better cruisers but the one I am building now is a MTB style (I like to call them SBMXs or suspended BMX because they are definitely not mountain bikes, but more like BMX bikes for old guys or people with bad wrists)

Anyhow, to get on with it, you will NEED a jig. You can not expect to build a frame without a jig and have it ride able, you also need a welder or access to one or know a welder and the various frame parts.



The jig.
Frame Jig
  Frame Jig

There are MANY designs for a frame jig, don't tell me this one was built wrong. I actually really like this design as it leaves much room to get at with the torch. The only bad spot is the other side of the BB shell is not accessible. Don't know what it cost me, I can't remember and it has been a work in progress. I have changed bits of it with every frame I have made on it. It is also I think my third Jig.



There is a program that at least was available free, Tubemitre.exe it will save you a tonne of time.


You will also need steel (In my case anyhow)

Raw tube
  Raw tube
Various 4130 tubing
  Various 4130 tubing

Tubing can not be welded in this condition, it MUST be clean. Shiny clean and then alcohol before welding. Also separate welding gloves so they are clean. Dirty welding gloves can put grease on your filler wire and that's bad.

Also frame bits.
Head tubes
  Head tubes

Pick a head tube.

Dropouts can be made with a grinder and either mild steel or something like 4150 which I like. 4150 must be pre heated a tonne before welding but can be left to air cool. Thin walled 4130 does not need to be heat treated after welding.
flag ricar
Posted: May 14, 2014 at 11:42 Quote
Tubemiter works very well with tubes like this.
photo
photo

It does not work so well on tubes like this (seat tube @ BB shell)
photo
The tube is not centered on the BB tube and also has the down tube protruding into it.

Coped tubes should not be sharp at the sides, you should grind them flat to the full thickness of the tube. If you leave that bit of metal there is is so thin it will melt and put too much carbon in the weld. Also, it is thin, you'll end up with reverse taper wall tubes.
photo
flag ricar
Posted: May 25, 2014 at 18:38 Quote
Well, when I started this I had lots of time. Now, not so much so please forgive the time in between. Still, no responses not much interest?

Regardless, I recommend starting with an easy spot, the BB shell and the Down tube. There is no angle to figure out and it's a pretty easy junction to get square. Tack the tubes and stitch them together, don't try to weld it all in one go or you'll get the dawn tube too hot.

I am not a professional welder so no, this is not the picture of a perfect weld, still I have not held a TIG torch in a few years (Sorry, GTAW) so I'm pretty happy with it. There are a few options for filler wire I'm using 310 stainless filler because I got it for a very good price, free. Don't tell me the draw backs of stainless filler, 310 is fine. 309 and 312 would be bad. Also 4130 filler is not suggested unless you will have your frame normalized after welding.

photo
flag Stinky1138
Posted: May 27, 2014 at 23:46 Quote
I think it's pretty interesting.
flag haglersp
Posted: May 29, 2014 at 9:40 Quote
You're doing a nice job explaining things. Keep it up. Oh and I've done some 4130 welding on a couple projects that take way more abuse than a bike ever would and I agree with your filler choice
flag ricar
Posted: Jul 26, 2014 at 7:52 Quote
Sorry this has been neglected. Had some issues with my "other bike" 1983 RZ350, leaking gas tank and too much riding my working bike, blah blah.... lots of excuses. Hope to get some more done in the next few days.
flag ChrisNop
Posted: Jul 26, 2014 at 17:23 Quote
Awesome information here, ive been interested in building a frame but havnt found a solid source of info, maybe other frame builders could post here and share
flag ricar
Posted: Jul 26, 2014 at 18:06 Quote
What info are you looking for?
flag ChrisNop
Posted: Jul 26, 2014 at 18:19 Quote
Where can I buy the headtube and bottombracket bits, im looking for integrated headtubes
flag ricar
Posted: Jul 27, 2014 at 4:23 Quote
Firebikes will have head tubes but unless they have changed I was unhappy with their design. They do work though and were the only place I could find them but that was a fer years ago. They will also make your BB shells but have a minimum order number.

Nova cycle supply and Ceeway may have stuff now. IMO if you can find a decent frame with a crack, cut the BB shell out of it and the head tube. Nothing happens to BB shells, and integrated head tubes are very strong as well but you don't want the ones that house cages bearings you want the ones that hold a 45* sealed bearing.

I ended up finding a guy who had a CNC machine on a pipe feeder make me some BB shells for beer. I gave him the tube and blueprints (and handed him a bearing).
flag huck1990
Posted: Jul 27, 2014 at 4:49 Quote
i love the idea of frame building ! awesome
flag ricar
Posted: Jul 27, 2014 at 11:23 Quote
ChrisNop wrote:
Where can I buy the headtube and bottombracket bits, im looking for integrated headtubes

I can sell you the one in the pic above, it is from Firebikes.

One thing I like about building my own frame is I can make the head angle fit my lowered fork.
flag ricar
Posted: Aug 12, 2014 at 19:32 Quote
photo

Building chain and seat stays are a real PITA. The worst part of frame building IMO. You are best off making a jig to hold the stays. This frame will have 110 spacing and that is my 110mm spacer.

My C-stay jig is pretty much a flat sheet the spacer bolts to and I can bolt the stays down to prevent them from moving/twisting.

I know square tubes are not the best, so I don't need to hear it but I still have an affinity for them. I have used them long enough to feel they perform well enough for me.

photo
flag ricar
Posted: Sep 2, 2014 at 17:03 Quote
Don't forget about brake posts available from places like Ceeway, or any number of frame part suppliers. Make a jig again, it's easier.

photo
flag ricar
Posted: Sep 2, 2014 at 17:10 Quote
Got ahead of my self....

photo


Have not put the brake posts on yet.

it's SHORT in the rear, nice so far. It's the first time using this head tube and they are longer than a standard with cups so the bars are now higher. I didn't like how high they were before but now I can't stand them and that's with no spacers at all. Guess I'll have to look into no rise bars.
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