I have been asked to make a replica of the vertical leg press below. My only question is about the portion that moves up and down along the round bar runner. I plan to use cold rolled round for the stationary portion and a DOM tubing for the portion that moves up and down. What material should I use to act as a bearing between the cold rolled and DOM. I have seen a dense plastic with holes drilled in the center but I'm not sure what the plastic is called. Or the type of bearing needed.
Thank you
The plastic is called UHMW for Ultra High Molecular Weight. It is a machinable plastic and is used as a bearing quite a bit in industrial applications. It comes in different thicknesses that I've seen up to 1" and more down to 1/32".
Last edited by HotRodTroy; 09-15-2020 at 06:43 PM.
Hot Rod Troy I have used that plastic in strips for squat racks in strip form. People like it because it does not wear the bar down (A section no one touches under 6"5")
I did not know it was in round form. I will have to check that out
They have cheaper alternatives : For 3/4" Shaft Dia.
7/8" 1 1/4" 1 1/16" 1/16" 155 lbs. @ 60 rpm 50 lbs. @ 60 rpm White -200° to 180° Made of FDA Listed Materials 57785K226 $9.29
Mcmaster isn't the cheapest, you could find on Amazon cheaper if you needed bulk. You could also make your own on a lathe. UHMW needs a nice sharp tool to get a nice cut.
good luck
Airco 250 ac/dc Heliwelder Square wave
Miller Synchrowave 180 sd
Miller Econo Twin HF
Lincoln 210 MP
Dayton 225 ac/dc
Victor torches
Snap-On YA-212
Lotos Cut60D
Primeweld 225 ac/dc
Primeweld mig180
Miller AEAD-200
They have cheaper alternatives : For 3/4" Shaft Dia.
7/8" 1 1/4" 1 1/16" 1/16" 155 lbs. @ 60 rpm 50 lbs. @ 60 rpm White -200° to 180° Made of FDA Listed Materials 57785K226 $9.29
Mcmaster isn't the cheapest, you could find on Amazon cheaper if you needed bulk. You could also make your own on a lathe. UHMW needs a nice sharp tool to get a nice cut.
Is that a common style bushing on press machines. I was wondering, how will those handle the compression from hitting that spring. The hammer effect might affect both ends? Seems like internal machining of the tubing might be necessary?
That is what I meant by internal machining. Otherwise, I suspect the parts could vibrate out or be damaged by the hammering? I would suspect even bronze would break or deform due to normal use on the machine.
What they did, is the way I would do it. Machine a seat for the bearing and slot for a lock ring of some sort to hold the bearing. Doesn't appear they are using a straight tube. No need DOM, if dimension is sole reason for selection. Just machine the ends to fit the bearing appropriately.
Design begins with the shaft size necessary to carry the load.
then a bushing should be seleced for wear, and clearance . If your concern with damage to a flanged bushing select a straight bushing.
Select a tubing whose od fits the bushing you have selected , keeping in mind that a larger wall thickness will have less distortion from welding (don't over weld).
Select a "push lock" retainer that works in the ID of the tube , that retains the bushing, and allows clearance for the shaft.
Most of the ID, and OD are standard sizes so you should be able to get away without having to do any machining of part to fit an internal fit, and retaining ring.
Good Luck
Airco 250 ac/dc Heliwelder Square wave
Miller Synchrowave 180 sd
Miller Econo Twin HF
Lincoln 210 MP
Dayton 225 ac/dc
Victor torches
Snap-On YA-212
Lotos Cut60D
Primeweld 225 ac/dc
Primeweld mig180
Miller AEAD-200
tbh i didnt fully read not sure if someone suggested it already. They come in diff sizes, they're not cheap though.
As a gym rat myself, a lot of people have asked me to make gym equipment and honestly its rare I can make it for the same price or less than they can buy it for.
I'd look for replacement smith machine or leg press parts, and build off them.
Last edited by BrooklynBravest; 09-24-2020 at 07:28 AM.
Thanks Guys. I have been out of town and unable to respond. I don't have access to a lath. At this point I think I'm going to try Wear-Resistant Cast Nylon Tubes https://www.mcmaster.com/84755K414.
Zach I agree about gym equipment, I work toooooo cheap
The guy has the cash so I started this build.
I had a Amish man drill out the plastic (he had it in stock) and he said he would turn it down on his lath so the plastic would fit in the pipe. I did not want him to fit it until I was done welding, too late
1. Do you think If weld the pipe (to hold the plates) to the pipe holding the plastic(see picture 1) and quench with water I will screw up the plastic? or The weld? I don't think I can get the plastic out. I have a press but may try.
2. The first picture is clearly the easiest method. I could run the pipe length wise to connect with the portions holding the plastic. Each side will need to carry 400lbs. The load will not be centered on the shaft however. Note the foot pad is not shown. I fear it may bind. What do you think? The kid thinks he can load 800lbs on press it, I imagine that is realistic.
The second picture shows a pipe centered to the runner. The pipe needs to be 10-12' long to get the needed wt. I don't want 400lb on and 1.5' pipe. If I put a gusset It may work. But It will have a **** ton off heat.
Lastly I can probably put a pipe in the center of the carriage, thus reducing the length of the pipes sticking out
Interesting. Does the plastic run the length of the tube? It you remove it, it may not go back in if the metal distorts from welding? I don't think quenching the weld is a good idea.
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Originally Posted by kb0thn
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