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Re: Leg Press Question

Thank you. I never think of amazon as a source. I'm old

I used the UHMW Linear which works great

Re: Leg Press Question

Originally Posted by Reebz

Could you take a picture of the glides? I just made a leg press for a guy and that was my only problem area. Is there a part number?

Saw this thread popup on my feed and realized I never sent a picture of the guides I was referring too in your mill thread. Since that one got off topic enough I figured best to reply to the thread the guides are most applicable to.

What I was referring to is just 1-1/4" solid chrome bar stock. Below are some pics of not the cleanest in the lot I acquired but you get the idea. I used these ones to slide a recently acquired mill on, hence the rough condition.

It has been at least a decade since I have frequented a gym, but I recall those glides always being linear bearings on the commercially made equipment. I do recall some made from tube steel with no liners on home built equipment though.

Linear bearings like kb0thn linked to on McMaster can be had for much cheaper from other sources like amazon and eBay. The 30mm version linked below is rated to 600lbs dynamic load each, 4 of them would get you over 2000lbs and the press you showed would not be a simple moment like the bearings are rated for. $150-250 should get you a decent setup.

https://www.amazon.com/uxcell-LM30UU...8&sr=8-25&th=1

If you wanted to cut cost even more you could also just use cheap roller bearings on square tube like the lower end plasma builds use. That would likely be smoother than using the plastic bushings and have sufficient capacity.


Attachment 1722219

Re: Leg Press Question

The kid got the money here is the prototype. The next one will be different with respect to the carriage. I feared it binding if the load was unbalanced relative to the CRR runner. I since have a different idea.Attachment 1722131Attachment 1722132Attachment 1722133

Re: Leg Press Question

Good news I used the press to remove the plastic, it came out easy. I'm going to weld it up Monday and see what happens.

Re: Leg Press Question

What will prevent it from being hammered out while in use?

Re: Leg Press Question

Yes runs the length of tube. I agree I don't like the idea of quenching. I have a few other ideas in mind. My head was spinning as I sleep

Re: Leg Press Question

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.

Re: Leg Press Question

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 outAttachment 1720778Attachment 1720779

Re: Leg Press Question

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

Re: Leg Press Question

https://www.grainger.com/product/4YR...87MP9:20500731


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.

Re: Leg Press Question

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

Re: Leg Press Question

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.

Re: Leg Press Question

Tapwelder
What would you suggest I do?

Re: Leg Press Question

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.

Re: Leg Press Question

Here is a better angleAttachment 1716385

Re: Leg Press Question

Attachment 1716383
This is something at the gym similar to my idea

Re: Leg Press Question

Stupid question, How do these stay in place?

Re: Leg Press Question

Originally Posted by Reebz

Good point. Bronze is an option

surprisingly , Bronze is cheaper(at least in this size). These are common machine parts, and should last a fairly long time, even in compression.

Attachment 1716302



Multipurpose Flanged Sleeve Bearings

These leaded bronze bearings are strong, wear resistant, and excellent at handling shock loads. They’re sometimes called 932 bronze bearings.


For 3/4" Shaft Dia.
7/8" 1/2" 1 1/8" 1/8" 1,500 lbs. @ 60 rpm 2,200 lbs. @ 60 rpm Required -350° to 450° 7815K45 $3.60

Re: Leg Press Question

Good point. Bronze is an option

Re: Leg Press Question

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?

Is bronze not an option.

Re: Leg Press Question

Originally Posted by albrightree

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

Attachment 1716258

https://www.mcmaster.com/uhmw-polyethylene-bushings/

Available in 3/16" to 1-1/2" shaft dia.

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

That might be perfect

Re: Leg Press Question

Originally Posted by Lis2323

Just for added info UHMW is also available in ROLLS of self adhesive strips in various widths and thicknesses.

I have used them on barbell storage racks.

I will look into that. I use 1/4 thickness in 2 and 3" widths frequently.

Re: Leg Press Question

Just for added info UHMW is also available in ROLLS of self adhesive strips in various widths and thicknesses.

I have used them on barbell storage racks.

Re: Leg Press Question

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

Attachment 1716258

https://www.mcmaster.com/uhmw-polyethylene-bushings/

Available in 3/16" to 1-1/2" shaft dia.

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

Re: Leg Press Question

You might take a look at pex tubing. It's cheap and durable.