after abit of advice.

[TGR]

Well I've got a project i've been working on and its came to abit of a stand still. The problem is i have fitted another motorbike swingarm onto my bike, so all that was left was to make a lower shock to frame mount.

So i made a bracket out of 5mm thick metal and the problem is i'm only getting about 4mm penetration out of my mightlymig 150 (which i found out is pretty much max after melting my torch internals).

So the way i see it is i have 3 options:

1. continue welding with 4mm penetration.
2. reduce bracket thickness to 4mm.
3. buy a bigger welder!

option one: i'm not 100% keen on, so i've drilled thru the bracket and frame and bolted them together. but it leave doubt in my mind on safety!

option two: I think is the only real option but been advised 5mm should be min.

option three: Not an option due to lack of current funds, and its a expense for a one off job!

so I thought i'd like to get you good people's view on my options.

 

[Ragnarok]

v it out with a grinder or file and weld it?
weld it from both sides?
or get an Arc to do the job? on thick metal I think they do at least as good a job as mig anyway.

 

[shenion]

Leave a gap or V-groove the joint and you can do 5mm.

Just tack it on and take it to someone to do the final weld.

 

[TGR]

Thank you for the advice so far, here's abit more info

I found a picture of my mock mount with the bolts:

the bike frame is tubing, so that creates a gap thats needs filled. Heres a crappy side diagram so you know what im on about. the grey between the tube (frame) and the square (mount) is layered welds. I have full penetration on the frame its just the 5mm that i can only get 4mm on.

 

[Ragnarok]

if you're welding 5mm to thin tube and you're getting full penetration on the thin tube and 4mm on the 5mm it isn't going to affect the strength in my opinion, because the tube will rip before the weld.

 

[Ratcatcher]

I thought bike frames etc were all tig welded these days?.
If you stick or mig weld the parts they will eventually break but generally down the sides of the weld due to the initial heat!.
A bike frames no different to the likes of quarry equipment and the machines are always going on the frames and always right beside the previous welds......
Years ago a friend was involved with side car motoX,his bike frame broke and he was advised to get it tig'd..He decided no just stick weld it which was done......
The first race it blew and nearly killed both of them.......
The best person for advice would be TechnicalAl,send him a message first.....


Rat.

 

[outofthefire]

If you stick or mig weld the parts they will eventually break but generally down the sides of the weld due to the initial heat!.

Rat.

Rubbish, they'll crack through poor design not because of which type of weld is used, the best frames in my opinion are brazed together and plenty of bikes are mig welded because its faster and cheaper than tig. If you weld 5mm onto thin tube and there is any flex the tube will fail around the weld first because the 5mm and the weld will be more solid.

I wouldn't drill through the frame unless you really have to. If you do though, you need to use crush tubes in the holes, i'd plug weld the holes onto the frame. If your not confident about your welding/welder i'd go for option 4 and get someone else to do it.

 

[piman]

Hello TGR,

I suggest you change the design, and weld on two lugs that fit around the tube as here:-http://www.demon-tweeks.co.uk/Search.do?method=view&s=chassis%20bracket

That is just to illustrate, you can easily fabricate two simple plate lugs without the cross piece.
That way the weld is radially around the tube not axially and so is easily welded and will be stronger.

Alec

 

[TGR]

Hello TGR,

I suggest you change the design, and weld on two lugs that fit around the tube as here:-http://www.demon-tweeks.co.uk/Search.do?method=view&s=chassis%20bracket

That is just to illustrate, you can easily fabricate two simple plate lugs without the cross piece.
That way the weld is radially around the tube not axially and so is easily welded and will be stronger.

Alec

I see where your coming from on that one also gives me the option to V the lugs for a full penetration.

@ thread thank you all once again for your help and words of wisdom