Shed built bike frame, welding T45 to bright mild.

[Pheasantplucker]

Hi,

I have been thinking about building my own frame for some time

You know what its like, you think it all through and try to find answers to tech problems!

So........here goes......................................................

I am leaning towards a Hossack inspired front suspension arrangement, mostly straight tubes of T45, Bandit motor.

Frame tubes of T45 but what material should the frame junctions be, the ones that take the  bolts through  the engine?

If bright mild is ok then what do you weld them together with, I will Tig the lot together, would A15 filler rod hold it together?

Any input would be gratefuly received.

 

 

[nlovien]

I can appreciate where you're going - went down the same route - you need to be carefull filtering out the noise if you use the internet for your source for info - summarizing the stuff I learned

1) can you weld T45 without post heat treatment ? - yes, as long as your working with relatively thin wall material i.e. the typical tube grade you'll be using will have a thin enough wall

2) TIG, MIG or stick ? - preference is TIG, although MIG can be used - if TIG do not use an old school scratch start welder, the scratch causes a high stress in the T45 that could lead to crack failure - if you do "Accidentally" cause a scratch arc with the tungsten, polish out the mark - especially if it leaves the tip of the tungsten on the tube

3) What wire ? - std issue A15 or A18 is recommended for T45 to T45 or as you say - std plate steel to T45 - avoid any SS wire

4) who welds versus brazes T45 - the yanks do, ok they don't call it T45 - high chrome alloy tubing, used for building roll cages / bike frames  / aircraft = they use TIG weld

5) what if, after doing a major structure weld, you take it out of the jig and it springs - i.e. shows signs of heat stress distortion ? - ( from an wise old welder) - stick it back in the jig and work your torch over the work - actual temp ?? ( please check) but cherry red is close, blanket it and let it cool down slowly, this will help to anneal out the stress 

6) large single run welds, or multiple small runs overlaying ? - best to go small versus big and build up, = less heat input + you stress relieve as you weld on weld

just so i'm clear, i'm not a professional welder, the above is what I summarised after speaking to professionals / reading and filtering stuff from the web + I have previously TIG welded to T45 tube mild steel brackets / tubes etc. - thrashed it / crashed it - never seen a weld or stress failure

[Pheasantplucker]

Thank you, very helpful.

[nlovien]

should have added "clean it" - not only grinding off any mill scale / rust etc.. - but removing paint / grease from a good distance from the weld (use 12" as a guide) - example: to help avoid heat distortion of the headstock I fit an old set of bearings / seats and a dummy stem - nipped up tight - last time I forgot to wash the bearings, couldn't work out where the soot was coming from ? - it was the grease creeping from the bearing to the weld - yeuck weld job - if you use TIG, also fit a 2nd argon purge line feeding into the inside of the pipe = this helps to prevent corrosion inside the pipe post weld outside - I make a small hole - tap to match a carb vacum spigot for the hose - having a vent hole is also a good thing, when you come to close up on a pipe at both ends, this hole prevents the pressure build up blowing the last sealing weld puddle

[Pheasantplucker]

Little pointers like this save so much grief, thank you.

[dupersunc]

No need to purge this stuff. it's nice but not needed. T45 is over kill really,  CDS or CFS3bk is plenty good enough.  EN8 for bosses if you use CDS, EN14 if you want to be fancy or use T45.

We use ER70 s2 rod for this sort of thing.

 

 

[Pheasantplucker]

On ‎05‎/‎01‎/‎2017 at 9:00 PM, dupersunc said:

No need to purge this stuff. it's nice but not needed. T45 is over kill really,  CDS or CFS3bk is plenty good enough.  EN8 for bosses if you use CDS, EN14 if you want to be fancy or use T45.

We use ER70 s2 rod for this sort of thing.

 

 

When I pick up the motor I will have to spend some time picking your brain........if you don't mind!

[homer]

Keep the heat at minimum. I like to use greater gas flow when working with tube joints. Tack weld it properly. Maybe the most important thing is a good fit up. When it sits nicely the heat imput is lower and there is less tension. If it is mine I would purge it. Maybe unnecessary but I like to do so.

I am also planning to build my own frame in the future. At the moment I am planning a frame jig for the project.

[Pheasantplucker]

16 hours ago, homer said:

Keep the heat at minimum. I like to use greater gas flow when working with tube joints. Tack weld it properly. Maybe the most important thing is a good fit up. When it sits nicely the heat imput is lower and there is less tension. If it is mine I would purge it. Maybe unnecessary but I like to do so.

I am also planning to build my own frame in the future. At the moment I am planning a frame jig for the project.

I would be interested to see a pic of your frame jig.

I Have been looking at the jigs that Wasp use and pictures of the Harris jigs too.

[homer]

There is not much to show at the moment. Just few drawings.

[homer]

Any updates @Pheasantplucker?

 

[SiBag]

Loads of good info...

[fredbcj]

nlovian was spot on with No5 ,treat the welding sequence like a bolt down routine on a cylinder head to cheat distortion,locking the joints first top on same joint left n right ,then bottom left n right ,then oppose welds as you go.areas like swing arm pivot areas it`s easier to pull the frame in ,so a tad more on the outside first means with the shrink you can keep the gap ,and if it does go wrong it can be relieved

[Pheasantplucker]

No progress unfortunately, empty bandit motor on the bench an 8x4 sheet of mdf with wheels and rake trail drawn on but that's all.

I have a few projects on the go at the moment and need to get these done to clear space, I'm also looking for a good pipe bender as the two I have aren't as good as I would like.

I have a plumbers three legged bender and an old crossbow type bender they are both hard work to produce repeatable bends. 

[nlovien]

I used a nasty cheap crossbow type bender and after a lot of error found a technique that achieved acceptable bends up to around +/- 75deg with 1 1/8" thin wall T45

1st - ditch any roller supports ( they create pressure points on the tube) and make sadle supports by cutting a decent thick bit of tubing in half - weld a bush at 90deg so it can pivot and follow the pipe

2nd - fine builders sand - make up some end stoppers ( I used a broom handle, wife is now complaining of a sore back ) - take you time filling - add a bit - tap tap - use a rod to pack it down, add more tap tap etc.. - then hammer in the top cap - basically - no air pocket

3rd - start with a bender guide for a larger diameter pipe - get some alloy tube that has an ID equal to or slightly less than the tube OD - make up reducer inserts to fit into the bender guide such that you sleeve it down so the final alloy spacer is a tight fit between guide and tube - reducers are made from pipe and can be formed into the bender guide using scrap tubing - the final alloy guide = the alloy pipe split slightly over the centre line

4th - sit the half moon and a bit more section of alloy tube into the bender guide - sit the tube to be bent on top of this ( the key point is your creating an interference fit)  - initial pressure from bender squeez's the T45 into the alloy and the alloy into the bender guide, you work this into the bender guide such that the alloy sleeve comes up over the guide more than half way over the T45 i.e. why you cut the alloy tube a bit more than along centerline = the T45 is now a really tight fit into the bender guide = lots of side wall support

5th-  this bit, I worked around it because I was taking hours to do it - when you start to 1st see a bit of pipe flex - make a ref: mark point and measure the bender guide travel relative to it - and with lots of small cycles and leaving it time to rest gradually work the bend - add +/- 5mm bender travel - hold - release - probably around 80% of the travel is pipe spring and 20% actual bend - keep adding small 5 to 10mm increments - release - measure - repeat

you cna stop and take the pipe out ( you'll need to hammer the alloy sleeve off the pipe / out of the guide) - check - re fit, and this is where accurately measuring the travel comes in - 1st it covers for the pipe spring and 2nd - after removing you can quickly go back to the point where you left off

At around 60deg, I was getting a bit of pipe flattening but not enough to bother me - put into perspective, compared to some of the bends in a Harris magnum 3 frame it was ok

oh and grease up the saddles to help the pipe slip through them

if your doing a largish bend diameter - you can work the pipe by moving it say 10mm either side of the initial point contact of the bender guide - i.e. start in centre a few deg. bend - slip pipe 10mm - repeat - slip pipe 10mm the otherway repeat and carry on sharing this pressure point until the deg of bend locks the tube into the guide

 

I have no idea if any of the above is science or bullshit, I do know that once I got a decent bend doing this - I stuck with it

[Pheasantplucker]

VERY slow progress, selling all the pipe benders I have collected as I have bought a Pro tools hydraulic bender with heaps of dies so should do everything I need.

Picked up a heap of 80x80x5mm box to construct a jig, it has to be adjustable as I have a harris and a rickman as 'Patterns' I wont copy either.

A friend wants a frame to put a 750n kwak in too.

Moving forward ...................................................slowly!

[Pheasantplucker]

Any thoughts on headstock material?

[dupersunc]

En8 or en14 if you feel fancy. 

you still after a dummy engine?

[Pheasantplucker]

Moving on slowly, only been 4 years!

[Dezza]

That looks just like a Harris Magnum frame.

[Pheasantplucker]

Similar geometry but tubes will be different, engine mounts different as this frame was for a GPZ.

[Wagola]

So not OSS ?

[Pheasantplucker]

Oil boiler going in when it’s done.