A question of strength

[stuck]

Hi all,

I want to make a tubular rear bumper with recovery points for my classic pickup, I intend on using either 3" or 4" OD thick wall tube with all mounting brackets made fom 10mm plate.

Question is will the two bumper mounting holes and the two holes in the rear cross member that used to hold the tow bar flat plate be strong enough?

I don't realy want to run bracing brackets down to the chassis rails.

Second question is do the recovery points realy have to swivel or can I just use 50 x 50 sections of 10mm plate with a 20mm hole in them welded to the main rail?

Edit: Chassis is in A1 condition.

Cheers,

Mick.

[bishbosh]

Firstly, 10mm plate is way overboard. 5mm will be fine.

The standard bumper mounts are of no value at all for a recovery point. You really need to fabricate something more substantial.

I would concentrate on the two holes in the cross member and fabricate brackets from the new bumper that "sandwich" the cross member so the two bolts are in double shear. IIRC the bolts are M16? or was I imagining that?

If they are only M12 / M10 then you really should be looking to use the holes on the chassis rails where the tow bar stays would attach too.

The above is of course only if you have a centrally mounted recovery point.

You don't need a swivel recovery point. Two bits of 10mm plate with a bit hole in them welded together to form a triangle ( the bumper is the third bit of the triangle) will be fine as long as your welding is up to scratch. I would look for a bigger hole than 20mm though so a good sized winch hook can go through it. Unnecessary shackles are just something else to get in the way / go wrong.

Alternatively, bend up some 20mm round bar instead of the 10mm plates.

[stuck]

Firstly, 10mm plate is way overboard. 5mm will be fine.

The standard bumper mounts are of no value at all for a recovery point. You really need to fabricate something more substantial.

I would concentrate on the two holes in the cross member and fabricate brackets from the new bumper that "sandwich" the cross member so the two bolts are in double shear. IIRC the bolts are M16? or was I imagining that?

If they are only M12 / M10 then you really should be looking to use the holes on the chassis rails where the tow bar stays would attach too.

The above is of course only if you have a centrally mounted recovery point.

You don't need a swivel recovery point. Two bits of 10mm plate with a bit hole in them welded together to form a triangle ( the bumper is the third bit of the triangle) will be fine as long as your welding is up to scratch. I would look for a bigger hole than 20mm though so a good sized winch hook can go through it. Unnecessary shackles are just something else to get in the way / go wrong.

Alternatively, bend up some 20mm round bar instead of the 10mm plates.

Thanks Bish,

Hadn't thought of fabricating triangular recovery points, bloody good idea.

The holes in the cross member are indeed +16mm so I'll use those.

Mick.