I've had a few rod guys give me their thoughts on fish plating frame rails. I'm doing a cruiser Yard Art Rod with a six cylinder and three speed manual transmission. Not a horse power king by any means. I haved used 2x3 .140 wall tubing **** welded in the straight lines, 45 degreed on the rear axle risers. Opinions? thanks, geno gene235@msn.com
Considering that all my welds (the ones that I do myself) look like ABC gum lumped on the joint - I don't feel qualified to comment (but I did, actually...didn't I?) dj
I'm of the mind set that there is a couple of things you really dont want to break...frames is one of em....I'd fishplate.... But I'm the king of overkill
Yes, I think "Why wouldn't you fishplate?" is an appropriate question. True, if the welding is perfectly penetrated, there's really no need. But for the 10 minutes it takes to whip up some fishplates and weld them on, it will eliminate a lot of doubt! I use them.
So far.... you guys are in the same rod here... I guess the ones that said "no need" are in need of parts that are left over from the crash!
better safe than sorry ....i use 2x3-2x4 .120 wall tubing for frames and fishplate anything that see's any stress ...1/8" plate is plenty for a street driven car ..and to top it off i bevel all my edges too
I fish plate everything. Consider it "Structural Insurance". Keep in mind that a fish plate should not have any straight edges. It should be round or oval, or an oblong shape. A straight edge can break at the weld, a curved edge cannot shear at the weld. I know alot of people cut square fish plates and turn them on corner to form a diamond shape. This does increase the strength of the fish plate over laying it flat by having the beads ran diagonally, but it's not as strong as a curved fishplate. Your welds may penetrate and be very strong, but the material may not be as strong as the bead itself, and can shear from the bead during extreme stress.
Familiar with the medium truck biz? Stuff like 1 ton duallys with 10ft flatbeds up thru rollback tow trucks? Those trucks are often lengthened brand new by the company that installs the bed, and in many cases will change lengths once again in their lifetime because the "bed" is often of greater value than the truck underneath. Know how they do all this? **** welds and a pair of fish plates per rail. Check a few of those trucks out if you're wondering what it takes in terms of proportion and shape. The day I learned that was the day I realized anybody with a mig, a sawzall, a couple pieces of string & a level can shorten or lengthen any frame in their garage. Safely.
Here's a quick MS Paint version of the right kind of fish plates. Round and Oblong. I used to do square fish plates and was told by a guy who owns a large industrial fabrication shop for oilfield to use round/oblong shapes.
While on the subject of fishplating, would it be considered alright to make a fishplate and place it inside of the frame's tubing that is to be joined and plug weld it? This would be done on both sides of the tubing of course.
Well, if he had put Rat Rod, he woulda got pounced on by the Stromberg hoarders. I thought it was a new twist on the original intentions of the term, before the poze-abillies, and rubber rats killed it. Yes, fishplate. Learned something myself, regarding the no straight lines theory.
If you cant weld you should plate. You dont see pipe fitters welding a patch on a welded joint for just in case. Or boiler makers do the same, that **** is under some big time pressure and heat. Car frames are cake joints. But it never hurts if you doubt your work. I have seen frames brake due to ****ty welds. Safety first. You may not be the only one who is affected by death caused ****py craftsmanship.
Gents, I need to add 4-6 of these and had just been considering the diamond shapes I see so often. So... where might I find circles pre-cut? Or, perhaps someone has a waterjet program that cuts actual "fish shapped" fish plates, just for fun? Gary
Although stronger than no plate, no where near as strong as one done on the outside and welded all the way around. As for the guy who suggested that plumbers don't do this, very different loads. It's not pressure on a frame but flex and the leverage loads are very high and in a much different load frequency.
When boiler pipes are sized, they're planned to be **** welded and have enough margin left without additional collars or plate. If it wasn't for this, boiler pipes would be half as thick as they are. Frames are a completely different situation Fish plates aren't really for "the weld" so the beauty of the bead is only one factor. They're for the heat affected zone. Because a properly welded **** joint is still at risk of stress cracks a half inch off the weld. It's the nature of how stress ac***ulates when you've got an inconsistency in material properties from heat affected zones, coupled with continuous flex & vibration. Fishplates are about pushing those stresses across a larger cross section of the frame rail and into unaffected material. You hit the nail with car frames being cake joints though. In the 70s GM just pointed the welder at the frame and waved it around with their eyes closed. It wouldn't suprise me if you could run un-fished frames for a hundred years either. Just wanted to point out the welder skill versus engineering angle. Good discussion here.
a vertical slice through the entire joint with one plate welded in between, will work also, and is alot cleaner......
NHRA rules say that the end of the fish plates can be rounded inward or outward (concave or convex) or they can be straight cuts but the angle of the fish plates have to differ from the angle of the **** joint. Hope this helps. CTJ
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