I need to fix a piece of steel to another. One piece is a bar about 20cm long, say 4-5cm wide and I dunno, 7mm thick or so, doesn’t matter. The other piece is bigger.

The forces will be twisting forces in the plane of the join, so I guess I am interested in the shear strength of the bond. Not sure of the forces involved really. It’s actually a mounting for a shock absorber onto a trailer suspension swingarm, so I suppose forces are quite high and with a fair bit of shock loading.

Some kind of super epoxy resin?

in typical stw style, i will ignore your question….

why not get it welded?

Chemical Metal is good.

I’ve held bits of car engines together with it in the past.
Though nothing with much load through it tbh.

id say there isnt to be honest. like said above. chemical metal or liquid metal is great for plugging holes in blocks or castings but as for holding something together and then have a force pushing is alot to ask….. worth a go tho?

I’d get it welded, epoxy will almost certainly shear (sooner rather than later) unless it’s some kind of super aerospace spec epoxy utterly expertly applied to expertly prepared surfaces, and even then, it’ll probably still shear when you least expect it to.

I could be wrong and some epoxy expert could be along any second, but I’d rather weld it and I’m a big fan of epoxy resin and gaffa tape.

well, lotus seem to think glue’s ok. the elise chassis is bonded iirc, but again, I’d just get it welded.

What is it that holds aircraft wings on again?

wouldn’t glue that, (and I’m also a glue fan)araldite 2 part worked brill on motorbike cranckcases but they’re not stressed.

weld, 7mm isn’t a lot but I had a klinn trailer and that’s nearly made of paper and it worked fine
can you plate – ie get 2 bits of metal that sufficiently overlap both parts, and drill bolt holes appropriately.

ps and sorry – what are the implications of failure, assuming you’ll be towing on a public road you might want to get somebody appropriately skilled and experienced to do it

What do the marketing people say?

It’s possible a DIY epoxy solution will be better than my welds… Any chance you could go for a bolted option?

A peeling force will bring the best epoxy joint undone. A couple of through fasteners near the leading edges usually fixes that.

if done correctly yes – preferably either a bar in a socket or two flat pieces with no peeling / twisting loads. You need a large area of contact of a very controlled space between teh two parts

Sticking a bar to another piece – unless it has a well supported socket no. Just get it welded

Raleigh used to stick their Dynatech frames together with Permabond single part epoxy.
http://www.permabond.co.uk/onepartepoxy.html
something similar is used to stick brake pads together (friction material / steel plate).
There is a rumour that people use glue and string to make whole bike frames, not sure about them though.

Yes it could probably work but…

utterly expertly applied to expertly prepared surfaces

This is usually the tricky bit and the reason why I trust planes that are glued together but not a DIY repair/build of the type you’re talking about.

That said, if you could do it and maybe rivet the plate in place too (to stop the peeling forces mentioned) then that’d be a good way to make it more secure.

BMW repair method for previously welded panels is now bonding. That also includes structural panels including chassis legs.

More to joining than welds and glue. Nuts and bolts? Rivets?

Glueing is not as strong as welding…unless you do it yourself and can’t weld for ****.

Glueing is not as strong as welding

sorry but that’s too general to be true. Bonding can be much stronger than welding.

😉

pfft…nonsense.

Not so…

http://blog.iloctite.com/2009/oem-excellence/structural-adhesives-are-replacing-welding-and-riveting

http://auto.howstuffworks.com/under-the-hood/trends-innovations/glue-car-together.htm/printable

Just found this which might be of interest. Finding out the results for your epoxy might help you.

ASTM D 1002 Test Method for Apparent Shear Strength of Single-Lap-Joint Adhesively Bonded Metal Specimens by Tension Loading (Metal-to-Metal)

ASTM D 2919 Standard Test Method for Determining Durability of Adhesive Joints Stressed in Shear by Tension Loading

ASTM D 3165 Standard Test Method for Strength Properties of Adhesives in Shear by Tension Loading of Single-Lap-Joint Laminated Assemblies

ISO 4587 Adhesives — Determination of tensile lap-shear strength of rigid-to-rigid bonded assemblies

ISO 9664 Adhesives — Test methods for fatigue properties of structural adhesives in tensile shear

ISO 11003 Adhesives — Determination of shear behaviour of structural adhesives — Part 2: Tensile test method using thick adherends

Thanks for the links…

The first supports your view to a degree, but the second doesn’t…

Structural adhesives are typically not good to use if the force acting on the joint would pull the two pieces apart as most adhesives have poor peel strength. Another poor location for a structural adhesive would be one where there are forces that would bend the joint, which could allow the joint to cleave and then peel

As this is a bike forum, I would suggest that for manufacturing bike frames for example…welding would offer a stronger join than glue.

Given that the molgrips stated…

The forces will be twisting forces in the plane of the join, so I guess I am interested in the shear strength of the bond. Not sure of the forces involved really. It’s actually a mounting for a shock absorber onto a trailer suspension swingarm, so I suppose forces are quite high and with a fair bit of shock loading.

I would suggest that in this case…glueing will certainly not be stronger than welding.

The first article you mentioned stated that glue is stronger for attaching body panels on cars…this I suspect would be true as the glue can be applied along the seam whereas traditional methods would use spot welding. If you were to apply glue in ‘spots’ as apposed to ‘along the seam’, then I doubt the join would be as strong.

Car manufacturing is all about cost and speed…I expect the main driver behind the use of bonding rather than welding is manufacturing cost and throughput rather then joint strength.

But then that’s just my opinion…

Bonding can be much stronger than welding.

is what I said. I know it’s not stronger in all situations, quite possibly including the OP’s

I hate taking things to have other people do them because they invariably look at me like I’m a complete loonie and it makes me feel stupid.

I could rent a welder and learn to weld – another skill never hurts. I can already solder and braze quite nicely.

Bolting would be lovely but I’d be slightly worried about compromising structural integrity, and more worried about not being able to drill through the swingarm. It’s a monocoque style thing made from two apparently cast halves (not sure but they are very hard and thick sounding) welded together.

The shocks came with mounting kits for a different chassis (which I thought I had, hence the original idea) and that chassis has a slot about 4cm long ish in the swingarm near the weld to accomodate the fixing brackets. I did think of this but again would be worried about integrity and the ability to actually do the cutting.

Another amusing STW thread!

so I suppose forces are quite high and with a fair bit of shock loading.

Don’t stick it unless you are a trained person with aircraft grade materials. It will break.

Why not weld?

I got some stuff (brake mounts) welded at a local welding shop – 4 joints welded, took him a couple of minutes plus some time leaving it to cool. Initially he wasn’t even going to bother charging me, in the end he said he’d take a fiver for it.

If you make sure it is prepared, and clamped in some way so that they have to do is weld it, and don’t want them to do any finishing (polishing or repainting or whatever) afterwards, then getting welding done really is dead easy and cheap.

Joe

Hello molgrips,

I’ve been riding a 1996 Trek 1400 road bike for a 18 months or so that uses bonded rather than welded frame tubes.
From speaking to the previous owner it would appear that the frame has been in almost continuous use (race bike, trainer, commuter) for almost all its 15 years and shows no sign of failure.

The butted male to female joints on the the frame are huge (clearly visible through the paint), which I suspect would alieviate any stress related issues, though the bonding itself seems fine.

TBH, I trust the bonded joints far more than I trust the Easton Program tubing itself, especially the slightly chewed through chain stay 😀 .

For a critical application, got to be worth contacting an expert to check before going ahead.
If glue was good enough for the de Havilland Mosquito, it’s good enough for me, but I’m sure the relevant application is critical, so best to be sure.

Spanner, there’s bonding and there’s bonding, and there’s strong and strong. Your bike application is quite different to my caravan application, and the glue used is quite likely different to what I would be able to get hold of.. and the materials are different too.