good material for making a push rod for a switch that broke?

[coppercone2]

I wanted to buy a sheet of material that is the same thickness and just cut the push rod out of it using a jig saw. (1/2 inch thick piece of plastic)
What material is going to be good for this that is durable?

I mean one of those rods that sticks out of the front panel and has a shitty plastic grip collet thing that is designed to break over a spring loaded toggle slide switch deep in the chassis (their usually like 1 foot long)

Mine snapped in two places, but I can still trace the shape on some material, so if I get something that is the correct thickness I can make a brand new one. Otherwise I will just solder one out of brass tube and put a insulator on the end.

And no you can't glue it, it was pathetically weak and easily snapped in even the place that was not damaged

If not I can cut a hole on the side and put a switch on it like a printer



My wavetek 395 had one of those piece of shit plastic hyper engineered for cost push rods in it that has like missing material because you know its going into fucking space and they needed to shave 5 grams off something and maybe to trick the boss that their doing engineering making some kind of i-beam shit instead of giving a solid part with 30% more fill on a critical component. Front panel fell apart too lol, two screws and a giant crumbly plastic flange is the way to go clearly.

Had the same problem on a sorensen unit but that one does not have a key pad in the way of the front panel, so I just drilled a hole and put a normal switch there. Ha ha this is going to end up having fiberglass added to the front panel to help it hold integrity. What a joke design

[Berni]

These days 3D printing is a good solution for it.

Even if you don't have a 3D printer you can often find someone you know who has one, or use one of the websites that let people advertise there garage 3D printing services.

If it is just a flat 2D shape you can also get services to laser cut you the shape from plastic, wood or even metal.

But yeah if the shape is simple and you got something like a bandsaw around you can pretty quickly knock out the shape you need from a flat sheet of plastic from the hardware store.

[coppercone2]

what plastic though is going to be actually not pathetic?  I want the best plastic, I am not impressed by 3d printer plastic for a push rod, its too weak. I need the best. I think I can make this part on a table saw actually for nice cuts, is just a check mark shape I need, I don't need the last part because I will replace that with a brass tube.

[coppercone2]

like the best thing from mcmaster

[coppercone2]

bought a new battery for it so I don't end up throwing the unit away, I am infuriated by this.

I am going to solder a brass rod (L Shape) to a cut in half brass tube that is cut down the middle and slides over the switch and then screw that down that to a strait piece of plastic that aligns with the hole. that way I don't need to cut complicated parts. You will need to undo the cover and seperate a screw because it won't fit into the front anymore, but whatever, I don't need that functionality and it will be way stronger.

Infact I just want to make it out of metal put a grounded stud on it with some flexible wire just incase even though the switch is plastic then it will be all metal. I don't know why a normal switch in HV equipment has so much less isolation then a fucking function generator switch that is isolated against 200kV. they are really paranoid about this thing for some reason. Maybe I am being sarcastic but the amount of trouble these plastic rods cause people makes me wonder.

[coppercone2]

I am going to take the split brass tube that fits over the switch, and braze that to a bent brass rod (90 degree) that will be brazed to a brass plate, and then I will put some screws to attach the brass plate to a plastic flat piece that will go out of the switch hole.

That way I have a insulated switch which has much higher strength and only one plastic flat piece (strong) made with complex geometry. You will need to un-do some kind of tensioning mechanism and screws to split it into two pieces if I need to remove the PCB, but IMO trying to keep it original is pointless. that plastic push rod can suck an egg

[tggzzz]

what plastic though is going to be actually not pathetic?  I want the best plastic, I am not impressed by 3d printer plastic for a push rod, its too weak. I need the best. I think I can make this part on a table saw actually for nice cuts, is just a check mark shape I need, I don't need the last part because I will replace that with a brass tube.

You can 3D print in many materials, e.g. ceramic, metals (gold, brass etc), paper, and many types of plastic.

Look at, for example, Shapeways to see the capabilities (resolution, accuracy, mechanical) of different materials. Create a 3D model using OpenSCAD, upload it to several manufacturers, choose the price/time that suits you. Since the cost is principally dependent on material volume (not shape), even a very crude model can give a good idea of cost.

Alternatively strengthen the rod by wrapping it in a fine wire, and slather epoxy glue all over it.

[SeanB]

For push rods about the best material is PCB substrate, as you can simply design it, and have it milled and shaped for you, and it is very strong in compression and tension, and, being a composite, it is not going to break or deform easily. Otherwise use glass filled nylon, and shape it by you, though it is murder on tool edges, unless you use carbide tooling. The old fashioned method was using bakelite resin, using cloth bonded with bakelite as the material. Strong, insulating, and a half billion tag boards and electrical panels worldwide still in use, at up to 400kV, are testament to the strength and durability.

[Ian.M]

The old fashioned method was using bakelite resin, using cloth bonded with bakelite as the material. Strong, insulating, and a half billion tag boards and electrical panels worldwide still in use, at up to 400kV, are testament to the strength and durability.

Yep. 'Carp' brand Tufnol, which is still available: https://tufnol.com/fabric-laminates/carp-brand/
but I bet you wont like the price!

[coppercone2]

well what one is good for a button, because the piece I will need is basically a flat plate that goes out of the front panel. I ordered the brass sheet (3/16), and I have the brass tube and brass rod and screws.

I thought to use PCB material but it seems like its not good for interacting with fingers. The dimensions I need are like 3/4 inch by 1.5 inch by 1/8 or 3/16, and it has to be OK for finger pushing,


Unless I change the design a little and accomodate something more complicated dimensionally then a plate that you push on. Its a little hard because I don't want it sticking out too much from a otherwise pretty flat panel with flat push buttons (i.e. have a cap on it).

[coppercone2]

I made a new mechanism. Not finished yet because it needs a little soldering but the way it works is

1) split in half brass tube soldered to a brass rod that is bent in the shape to bring the rod down to the slide area
2) brass plate with two tapped holes soldered to the brass rod (drill a hole and flow solder the rod into place)
3) teflon sheet of approximately the same thickness as the chassis thing with two holes in it

so you put the brass tube on the switch
then you put the teflon piece through the front
then you insert two screws to hold it together


I think its a good repair, I just need to make sure the brass tube does not slide off the switch, and make sure it does not press into it too hard, but the original mechanism was just some plastic bendy crap that slid over it so how much worse can it be? I made sure the tube is not too tight and then I guess I can put some zip ties over it to tighten it down.

its a little wimpy but the thing is the teflon when its short seems to do a OK job. I am sure another plastic would be better but I happened to have teflon sheet approx the same thickness as the original push rod chassis exterior protrusion. It seems to be stiff enough for a short linkage.

[coppercone2]

been working great. Turns out you can assemble it externally and fit into the chassis from the top when trimmed. Putting heat shrink on all the metal parts is good enough, no need to paint, and the heat shrink keeps the collet cut tube collapsed on the switch.