Written by: Kyle Divine
In this tutorial, I have a couple of options for a rack attached leg curl and leg extension machine that won’t break the bank.
Cost of materials: $100-$120
Difficulty: medium to hard
Time to build: about 2 hours
The rest of the article includes:
Would You Rather Not DIY?
Titan offers a solid option that will take up more space than this attachment but will take no setup time or time to create.
Video
Instructions
This project idea was inspired by the Sorinex Mule, which has a small profile and allows for standing hamstring curls. Priced at $699 it is something that many home gym owners can’t justify purchasing. Fortunately, I came up with two designs that have more functionality at a lower price tag.
This project starts with cutting the square steel tube.
The length of this piece is determined by the distance from your ankle to your knee. For me, it is 16 inches.
The easiest way to cut metal pieces is to use a metal saw, but I don’t have one of those, so I use my angle grinder with a metal cut off wheel. It’s a little harder to cut straight lines with this, but it gets the job done.
Next, I cut the 3/4” threaded rod. The length of this will depend on the pads you get. I am using 8” pads and I cut the rod to 21.5 inches
Now it’s to drill the holes into the steel tube. You don’t need a special kind of bit to drill into the steel. I drill a 3/4” hole for the threaded rod.
Close to that one is a 3/8” hole for the weight pin.
The third one is another 3/8” hole and this one is to attach to the caster.
Here are the measurements and the hole spacing.
I use my belt sander to smooth out the rough edges.
The caster is pretty easy to take apart. Replace the wheel with the steel tube and tighten it back up.
I remove sharp edges on the inside with a small piece of sandpaper.
Insert the threaded rod, add the lock washers, and center it. When that’s good to go add the nuts and tighten.
For the weight sleeve, I’m using a 2” thick wood dowel. I cut it to 10” and move over to the drill press.
I drill start off with a normal length 3/8 inch bit. I go as far as I can with that one and then switch out to a 12” long bit.
The dowel is so long that I need to raise the table a few times to get all the way through.
It is important when drilling this far into something, that you have a pattern of drilling, then bring the bit up, drill a little farther, then bring the bit up and so on, that way you’re removing the excess wood chunks. Otherwise it gets clogged up and can cause the bit to get stuck.
I round the edges of the dowel with my round over bit on the table router, you can also accomplish this with sandpaper.
Before assembling, make sure your weights fit on the weight sleeve. My York plates fit just fine but my Ivanko and Rogue plates don’t.
The solution is to sand down the dowel a little bit. You can do this with any kind of sander or even just sandpaper, I prefer to use a belt sander because it is way faster.
I use a carriage bolt to attach the weight sleeve because I like how it sits semi-flush with the end of the dowel. I hammer in the toque washer, doing my best to align the holes.
Put the end of the bolt through the steel tube, add a washer, and fasten the lock nut.
With all of these pieces being different colors, I add some black spray paint to give them a uniform look.
This is where the build process splits for the two different options. Option 1 utilizes a 2×6 going across the front of the power rack.
My power rack is 48 inches across, with 3×3 posts and 1” holes. If you have a rack with different dimensions, you’ll have to adjust accordingly.
In order to figure out where to drill the holes for the bolts, I clamp the 2×6 onto the front of my rack, make sure it is level, and mark the holes with a pencil.
Once those are marked, I use a 1 inch forstner bit to drill the holes into my 2×6.
I use 2×4 scraps for the next two pieces. These are small, watch your fingers!
The 4×2.5 piece sits on top, in the center. I use a mending plate to fasten it to the 2×6.
The 4×3.5 piece goes on next, also in the center but in the front on the bottom. I attach it with a couple of screws in the front and another screw from the back.
I paint the wood and after the paint dries, attach a rubber stopper on the 4×3.5 inch piece.
Now it is time to make the pads. These are slightly more complicated than the pads I’ve made previously because they need to wrap over the top.
If you don’t want to bother with upholstery. You can use a foam gym tile instead.
The goal is to cut the foam out in the size you need it. Then cut the material in the same shape, but a bit larger so you have room for staples.
In order to hide the cuts, I fold both sides under to fasten them. On one side I am able to use my stapler, on the other side I hammer in black staples. I know it’s not beautiful but it’s the best solution I could come up with.
After the sides are secured, wrap the top piece and bottom piece around and staple them in the back.
Once that is done, I detach the caster base so I can mark where to drill the holes.
I attach the caster base with 1/4” bolts. I pre-drill the holes beforehand and the holes go all the way through the plate on the back.
I add a nut, a washer, and a foam pad on each side, then add washers and nuts on the end to keep the pads in place.
It easily attaches to the front of my rack. Add a bolt and nut on each side and it’s ready to use.
The biggest benefit of this design is the ability to work both legs at the same time.
The design for option 2 is more compact but just as effective. The downside is that there’s no easy way to work both legs at the same time.
The build process is pretty similar.
On this one, I drill through the mending plate with the drill press before attaching it. It’s much easier this way.
I attach the mending plate with a few screws. Remember, there are a lot of screws going into this wood, it can be tricky to coordinate making sure they don’t run into each other.
I use 3 lag screws to attach the top piece of wood, rather than two wood screws.
The 4×3.5 piece goes on the front with two screws going into the back through the mending plate.
After painting, the rubber stopper goes on.
The foam and fabric pieces are about the same size on this one.
I don’t want to block the holes so I mark a line where my staples need to go.
What makes this one easier is that the fabric can stretch around the side and be stapled in the back.
Then wrap the top and bottom around to the back and staple them.
Repeat on the other side.
Connect the caster base and take it over to the power rack.
Unfortunately, I didn’t realize the nuts are preventing it from sitting flush. If I had attached the caster base ½ inch over, it would be fine.
I have a quick fix. I cut down a couple pieces of UHMW plastic, attach them to a board with the proper holes spacing, and drill one inch holes.
Once this is done, I attach the pieces to the back. Now my rack is protected.
You’ll want to tighten the bolts up real good so it doesn’t move around.
Materials
| RTMaterials | Link #1 | Link #2 |
| 8ft 2×6 | Home Depot | |
| Steel square tube | Amazon | |
| ¾ inch threaded rod | Amazon | |
| 3 inch fixed caster | Amazon | |
| 2 inch dowel | Home Depot | |
| 1 inch thick upholstery foam | Amazon | Home Depot |
| 1 yard of black vinyl fabric | Amazon | |
| 3 inch wood screw | Home Depot | |
| 2.5 inch wood screws | Amazon | Home Depot |
| Black spray paint | Amazon | Home Depot |
| 1 – Mending plate | Amazon | Home Depot |
| Rubber stopper | Amazon | |
| Black double pointed tacks | Amazon | |
| 8” foam pads | Amazon | |
| Foam gym floor tile (optional) | Amazon | |
| UHMW plastic (optional) | Amazon | |
| 1 – ⅜ torque washer | ||
| 1 – ⅜ carriage bolt 12 inches long | ||
| 1 – ⅜ washer | ||
| 1 – ⅜ lock nut | ||
| 2 – ¾ lock washer | ||
| 4 – ¾ washers | ||
| 6 – ¾ nuts | ||
| 4 – 1/4” bolts, 2.5 inch long with lock nuts and washers | ||
| 2 – ⅞ bolts, washers and nuts |
Tools Needed
| Tools | Link #1 | Link #2 |
| Dewalt sliding mitre saw | Amazon | Home Depot |
| Dewalt cordless drill | Amazon | Home Depot |
| Bosch cordless drill set | Amazon | |
| Drill press – alternatively, the holes can also be drilled using a cordless drill | Amazon | Home Depot |
| Angle grinder | Amazon | Home Depot |
| Belt sander | Amazon | Home Depot |
| Dewalt random orbit sander | Amazon | Home Depot |
| Staple gun | Amazon | Home Depot |
| 1 inch forstner bit | Amazon | Home Depot |
| 12 inch long 3/8 drill bit | Amazon | Home Depot |
| Bench Vise | Amazon | |
| ¾ inch drill bit | Amazon | |
| ⅜ drill bit | Amazon | |
| ¼ drill bit | Amazon | |
| Clamps | Amazon |
I can pay Sorinex $699 or buy close to $800 in tools and materials and have the same thing?
Sounds like not having access to tools is a you problem. Don’t be a jerk.