Chassis fishplates

Hi all. Question, just starting chassis mods and need to add fish plates to chassis where cross members join.
The question is I have two members only about 400mm apart, is it ok to have separate fishplates that will only have about 80mm between the ends or should I run one long plate to pick up both cross members?? TIA

Pictures or a drawing would help us understand what you're trying to accomplish.

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What is an mm? If you put 400 m&ms in a row how many inches long is it? [S

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Brunno; I see you haven't quite embaced the concept of the metric system yet.

Yum M&M's!!!
Alright. So if I have a fishplate approx 10" long then a 3" space and then a 14" fishplate is that acceptable or should I just do a 27" long fishplate as that seems very long?[S

It will just add more strength. It would be nice to see pics of what you are doing, your plates seem kind of long but I'm not sure of what you are doing.

Your definition of a fishplate may differ from mine (and ours).

I was taught to use a fishplate to repair a cracked frame, or splice frame sections.

We hope to help and give good advice.... but we need specific information to give it.

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Yeah, we really need a drawing or pictures. I can't envision what your setup looks like at all.

Don

I think he may be referring to boxing the chassis sections where the crossmember attaches but I'm not sure. This is definitely not a fishplate question...

I'm guessing he has joins in chassis rails, just 16" apart, so he's asking whether to run one 'doubler plate' (fish plate) all the way along covering both joins, or run two separate doubler plates.

If the chassis is good steel, properly welded, it won't really need a doubler plate, but I've used them, before just for peace of mind, and because I'm not a pro-welder.

Either way will give the necessary reinforcement. Just personnel preference really.

I'm trying!!

Hope this picture makes since?
The chassis is from a 1993 hilux so is already strongly boxed.
Due to different engine /trans combo I need to make a new g/box crossmember and the engineer wants me to "fishplate" with 3mm steel at point of attachment.
I am also modifying torsion bar mounting point so thought I should also put a 3mm plate as per the picture where it attaches.

So original question do you think it is ok to have two separate plates with approx 3" in between or just do one very long plate for both attachments?

Or am I over engineering!?

Cheers guys hope this is clearer

Thanks for the drawing and explanation, spoon.

Your plan seems sound to me... plates increase the welded "footprint" and distribute the stresses over a larger area... so, I do not see a problem with separate plates, especially coupled to a boxed frame.

You could run a continuous plate to cover both members... and I'd expect that to survive an engineer's scrutiny, but separate plates (elliptical in shape and nicely welded) might prove superior in appearance and therefore, pass inspection quickly...

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Thank you

Thank you Dr Crankenstein, the engineer didn't mention a plate under my torsion bar mounting but I'm adding it anyway.
I agree thinking separate plates will look better just wasn't sure if it'd cause a hassle with the 3" space. But as you say the boxed chassis should be up to the task and the extra plates help with a bigger footprint.
Sorry about the sketchy explanation for a start but we got there.

I look forward to spending more time on this great site as my build progresses. [

If the frame is already boxed, I don't see a need for another plate on top of that. That's the problem with having to put up with somebody from the Govt looking over your shoulder all the time, but I guess you do what you have to do.

Bamamav said:

That's the problem with having to put up with somebody from the Govt looking over your shoulder all the time, but I guess you do what you have to do.

Click to expand...

Indeed:

"I have no idea how to do your job, but my book tells me you're doing it wrong"

At the end of the day I need engineers signature so I can get it registered I guess.
I will stick up for my engineer he spent a lot of time going over things and shared some great ideas. Guess they're not all the same!!

I wish I had an engineers education. There is so much that most of us just guess at. And we think if the plate is thicker or we make it all heavier, that it's better. Often it is not. One thing I try to maintain is keeping any welding perpendicular to the frame to a minimum. A weld all the way across a frame section is a fracture line. Especially worse on the bottom where the joint is in extension. I like the oval reinforcements, seems like they spread the stress better and leave very little straight line perpendicular stress points. Although I think it might be better if all one piece because you have that space in between where it has been hot from welding and you really don't know the metallurgy of a factory frame.

LMAO!!!

bruno said:

What is an mm? If you put 400 m&ms in a row how many inches long is it? [S

Click to expand...

Bruno you make me laugh....the guys being serious I think...but...oh forget it...I'm still laughing....[cl