Is this fixable?

[Duplicitous]

I have a Hoist D400 leg curl/extension combo that I just recently reassembled after purchasing it a couple months ago. The top plate on it was sticking badly, so I took it off to inspect it. I found the insides of the holes that slide over the guide rods covered in some type of dried up grease/oil. Thinking that was the problem, I thoroughly cleaned it, applied a fresh coat of silicone w/ PTFE to the guide rods and put the plate back. No improvement. My next thought was that something the previous owner applied caused the plastic inside the holes of the plate to permanently swell. of course, they may have smothered the thing in grease out of frustration after experiencing this sticking problem. I called Hoist service to ask if they had ever encountered like this. The guy at Hoist told me he had not encountered this issue before, but he also said that the machine was discontinued (in 1999) long before he ever joined the staff. His suggested replacing the top plate, but after some research he discovered none of the plates they currently manufacture would even fit.

So my question is simply: Is there a relatively easy way to get this machine working? My only real thought at the moment was to either: (a) take a Dremel to the plastic on the plate that slides over the guide rods to grind it down or (b) cut the plastic entirely and replace it with an appropriately sized plastic grommet. Of course I don't know what the real world consequences would be of taking either approach since I have never tried it. Anyone ever come across anything like this? Any suggestions?

[Mech6]

I have a Hoist D400 leg curl/extension combo that I just recently reassembled after purchasing it a couple months ago. The top plate on it was sticking badly, so I took it off to inspect it. I found the insides of the holes that slide over the guide rods covered in some type of dried up grease/oil. Thinking that was the problem, I thoroughly cleaned it, applied a fresh coat of silicone w/ PTFE to the guide rods and put the plate back. No improvement. My next thought was that something the previous owner applied caused the plastic inside the holes of the plate to permanently swell. of course, they may have smothered the thing in grease out of frustration after experiencing this sticking problem. I called Hoist service to ask if they had ever encountered like this. The guy at Hoist told me he had not encountered this issue before, but he also said that the machine was discontinued (in 1999) long before he ever joined the staff. His suggested replacing the top plate, but after some research he discovered none of the plates they currently manufacture would even fit.

So my question is simply: Is there a relatively easy way to get this machine working? My only real thought at the moment was to either: (a) take a Dremel to the plastic on the plate that slides over the guide rods to grind it down or (b) cut the plastic entirely and replace it with an appropriately sized plastic grommet. Of course I don't know what the real world consequences would be of taking either approach since I have never tried it. Anyone ever come across anything like this? Any suggestions?

Remove old bushings, insert new bushings.

[Duplicitous]

Remove old bushings, insert new bushings.

Well, that was essentially my plan. However, they appear to be permanently affixed to the plate (and the tech at Hoist said he believes that is the case also). In the event they're not, do you happen to know how to remove them short of breaking them off (which would be a bit challenging but obviously doable)? I know they make various types (thread, snap, etc.) of plastic bushings, but have no idea what Hoist uses and have had no luck trying to get them apart using reasonable (but not excessive) force.

[Mech6]

Well, that was essentially my plan. However, they appear to be permanently affixed to the plate (and the tech at Hoist said he believes that is the case also). In the event they're not, do you happen to know how to remove them short of breaking them off (which would be a bit challenging but obviously doable)? I know they make various types (thread, snap, etc.) of plastic bushings, but have no idea what Hoist uses and have had no luck trying to get them apart using reasonable (but not excessive) force.

Bushings are pressed in. So you should be able to press them out. Barring that they could be bored out but that requires a mill.
Post a photo.

[Duplicitous]

Bushings are pressed in. So you should be able to press them out. Barring that they could be bored out but that requires a mill.
Post a photo.

Top




Bottom

[Greybird2]

Find a socket that fits perfectly and try tapping it out from the bottom.

[Duplicitous]

Find a socket that fits perfectly and try tapping it out from the bottom.

I just gave it a shot. It didn't budge.

[Mech6]

I just gave it a shot. It didn't budge.

You need a press. Then it would come out easily.

[Slick80]

I just gave it a shot. It didn't budge.

Is it possible that the machine was assembled on uneven flooring so the guide rods themselves aren't perfectly parallel?

[Seatard]

After checking that the guide rods aren't out of alignment, and that the bushings are really too small, you can make a simple puller with a long bolt or all thread, a couple nuts, washers, and two sockets. One socket fits over the bushing on the top, one fits inside the hole on the bottom, squeeze them together with the bolt.

[Duplicitous]

After checking that the guide rods aren't out of alignment, and that the bushings are really too small, you can make a simple puller with a long bolt or all thread, a couple nuts, washers, and two sockets. One socket fits over the bushing on the top, one fits inside the hole on the bottom, squeeze them together with the bolt.

Initially I thought alignment might be an issue as my basement floor is not completely level, but I checked and the rods get stuck even with only a single rod in.

Funny you should mention the makeshift press as I was just watching videos on that on YouTube a couple hours ago. I have a lot going on this week, but I'm going to give this a shot on Friday. Then I just have to find replacements.

[fedewab2]

Can you reassemble and test the machine w/ the top plate omitted? If so, it would be nice to verify the problem is only the top plate, and not something that affects the entire stack. Then, I think a first attempt at solving the problem would be simply increasing the ID of the bushings while still installed in the plate. Perfect probably is not necessary. Maybe an appropriate size wood dowel, or similar, wrapped with sand paper. Many options.

[Duplicitous]

Can you reassemble and test the machine w/ the top plate omitted? If so, it would be nice to verify the problem is only the top plate, and not something that affects the entire stack. Then, I think a first attempt at solving the problem would be simply increasing the ID of the bushings while still installed in the plate. Perfect probably is not necessary. Maybe an appropriate size wood dowel, or similar, wrapped with sand paper. Many options.

Well, it won't function without the top plate as that is the piece that contains the post. When putting the plates over the guide rods during assembly though, all of the plates slide on easily except for the top plate.

I haven't had time to return to it, but I'm hoping this weekend I can try to get those bushings out or maybe try to expand the ID as you said via some method.

[ampire]

Well, it won't function without the top plate as that is the piece that contains the post. When putting the plates over the guide rods during assembly though, all of the plates slide on easily except for the top plate.

I haven't had time to return to it, but I'm hoping this weekend I can try to get those bushings out or maybe try to expand the ID as you said via some method.

You should be able to make a bushing/bearing puller using the methods detailed above. In case you need to return things to the original setup, those factory original bushings should be removable without damage to them using the puller. Otherwise, you could just cut or hammer them out.

Replacement bushings can be purchased from McMasterCarr in various sizes and materials. You may be able to buy a bushing that is slightly larger in internal diameter.

If you don't have an arbor press, the new bushings can be pressed in using a large bench vise.

I wonder about the alignment of the machine as a whole being the issue, as in the guide rods are not parallel, but you tried running the weight plate up and down one rod and it doesn't move very freely, so than it isn't an alignment issue but a tight bushing issue.

Regardless have you tried measuring the lateral distance between the rods at the top and the bottom to see if the rods are properly parallel and 90 degree perpendicular to the machine base?

[fedewab2]

Well, it won't function without the top plate as that is the piece that contains the post.

Well, that seems obvious now that you write it out for me.

When putting the plates over the guide rods during assembly though, all of the plates slide on easily except for the top plate.

I haven't had time to return to it, but I'm hoping this weekend I can try to get those bushings out or maybe try to expand the ID as you said via some method.

If there is not an alignment issue, I wonder if the bushings in the top plate are incorrect replacements; a failed fix attempt by a previous owner. I have little experience w/ maintaining selectorized equipment. How often do bushings in this specific application wear out of fail?

[vristang]

I would pull it apart and take some measurements of the bushings, and the rods they slide on. This will tell you if there is an interference issue...
It could also be that the bushings in the plate are not parallel, or the rods are not parallel at the point of sticking, or the rods are bent/tweeked. Rotating the rods may or may not help?

If the bushings are undersized, you shouldn't need to remove them, but simply hone them out a little...
Automotive shops should have smaller hones typically used for brake calipers and such.
Or, simply shove a rolled up scotch brite pad in there and attach to a drill motor. It doesn't need to be precise or close tolerance, it isn't rocket surgery.

[RioDPax]

Drill or press both out, order some correct sized bronze flange bushings at mcmastercarr and press them back in. It would be simple for me, but I got a pretty complete metal shop and have done a lot of this over the years. I know the machine shops around here charge $100 an hour no matter how small the job.

[Mech6]

Drill or press both out, order some correct sized bronze flange bushings at mcmastercarr and press them back in. It would be simple for me, but I got a pretty complete metal shop and have done a lot of this over the years. I know the machine shops around here charge $100 an hour no matter how small the job.

I wouldn't use bronze for this. Composite/nylon/uhmw/whatever is going to be much quieter because you want them 1/16" oversized. Not supposed to be slide fit. They're just to guide the top plate/stack and having them with no loose is going to make them bind.