Fish Plates

[Tiger Tamer]

I need to add some fish plates to areas of my chassis to weld brackets for my 4 link conversion. The Hillman chassis as far as I can measure seems to be approx 1.3mm thick. Just folded sheet metal really. 

I have been told to use 4mm plate to make fish plates out of. I have the hobby car tech manual but they don't give that much info on their design. I would think you would make them with radius corners and cover twice the area? of the bracket you will weld to it.

I see also of pic's on the net some have holes drilled in them as well to plug weld the plate on as well as the circumference. The hobby car manual doesn't mention this. Though I can see it could have merits.

 Has anyone done this on their builds and no what you need to do. I will tack them in for now and talk to the certifier about them.  Thought I would ask here. 

[RXFORD]

Anything thicker than 3mm to 1.3 is a bit silly in my opinion. Kinda like hanging a brick off paper.

The heat affected zone from blazing 4mm+ to the thinner material would counter any benefits of having a thicker load plate imo. 

 

I would use 3mm but make the plate fairly big/long to spread the load. It will need to span the full height of the oem rail or xmember to meet requirements. I probably wouldn't fully weld it to a chassis that thin either. Just stitch weld to keep the haz to a minimum. Radius corners and 'Fish mouth' or 'diamond' the ends where the plate crosses perpendicular to the rail instead of just having a square cut. Adding a few plug welds here and there is sensible too. 

 

I would definitely speak to the certifier you plan to use about it. There may be additional things he would like to see being that its basically sheetmetal. 

[Tiger Tamer]

19 hours ago, RXFORD said:

Anything thicker than 3mm to 1.3 is a bit silly in my opinion. Kinda like hanging a brick off paper.

The heat affected zone from blazing 4mm+ to the thinner material would counter any benefits of having a thicker load plate imo. 

 

I would use 3mm but make the plate fairly big/long to spread the load. It will need to span the full height of the oem rail or xmember to meet requirements. I probably wouldn't fully weld it to a chassis that thin either. Just stitch weld to keep the haz to a minimum. Radius corners and 'Fish mouth' or 'diamond' the ends where the plate crosses perpendicular to the rail instead of just having a square cut. Adding a few plug welds here and there is sensible too. 

 

I would definitely speak to the certifier you plan to use about it. There may be additional things he would like to see being that its basically sheetmetal. 

I have cleaned off more of the underseal and made up the brackets to weld to the chassis for the upper arms. I will leave it there until I talk to the certifier or he calls in for a look. I did do some practice welds with 3mm to 1mm and had no blow through the 1mm. 

Cheers