Designing a Lat Pulldown Machine which can "Lift Heavy Weights"

[dipenchatterjee]

Dear Friends

I had to delete my earlier post as I could not come across the appropriate thread to post my query.

I seek your advice in designing a home made lat pulldown machine (with low pulley) which can lift upto 150 kilograms of weight plates. I intend to use 2 inch by 2 inch square rods (unless you guys feel otherwise) and the maximum height of the maximum should be 6 feet i.e. 72 inches. Draft 2D diagrams are attached for your reference.

I wanted to understand during execution of LPD exercise, when the weight comes of the ground and the center of gravity moving up, is there any chance that the machine may shiver or topple down? What may be possible ways to prevent that (considering that I do not intend to use a fixed base i.e. fastened to the ground by screws or make the base unnecessarily heavy using stone filled rods / heavier rods).

I seek your step by step guidance and other suggestions if possible.

Regards
DC

[vic84875]

Fine but, your design needs work. The second one is the better, but it needs more pulleys for a total of 7. Look at the internet, and copy the design of 7 pulleys. Can be done with less than 7 pulleys, but pulley are cheap.

Cable need to be: steel 5-6mm diameter. The pulley 11.5mm diameter: must have a bearing built in.

They should be cover in some kind of polymer (wrapped from the manufacturer). You can choose different material for pulley and the cable, but in time, the ''harder'' will eat the ''softer''. (That happend in the 70's with pulleys of cast iron and steel cables.). It is better if the cable and the pulleys are wrapped in the same polymer.

If the guide is square, buy a polymer/nylon sleeve, (using the nylon sleeve, you avoid a metal-metal movement).
Use silicone to lubricate the guide.

For the structure: structural tube 30mm x 30mm x 1.6mm; or higher!.

Preferable the square guide must have some electrolitic treatment; chrome, zinc, galvanized,etc. If you can not afford any, the steel tube must be polished regulary, it just needs some bi-monthly care to avoid rust, rust increases friction.

Good look.

[cthulhupun]

Isn't this the point when most people just switch to weighted pullups?

[Vermonter]

Things that would reduce instability:
1) Fastening it to the floor
2) Heavy fixed weight at the base
3) A Wider "footprint"

Did you not want this attached to a power rack for a reason?
Is space a concern?
Why not add a weight rack to the sides to anchor it with unused plates?

*shrug*