Step 1: You Will Need:
- Woodglue, any reputable brand
- A Jigsaw - to cut out the circular shape of the rings. Mine was a deWalt, anything decent will do.
- A Drill and drill-bit to make a hole for the jigsaw to cut out the inside circle. Something bigger than the width of the jigsaw blade.
- Clamps or a method of clamping the sheets of plywood while the glue sets. I used some Irwin Quick-Grip clamps aswell as a bench-mounted Vice, and also some regular vice-grips. You could probably get away with putting some heavy weights on the plywood on the ground.
- An Orbital Sander or Angle Grinder with Sanding attachment. I used a Hitachi G12SR3 Grinder with a sanding head. It needs to be pretty powerful to sand the plywood quickly. it's 730W, 11,000 rpm and weighs 1.4kg. I wouldn't go much heavier as a lot of the sanding I did with one hand while holding the wood.
- A Compass for drawing circles
- A Ruler
- A Pencil and a Marker (that's 'sharpie' for you yanks)
Step 2: Make Some Plywood!
So take your sheets of plywood minimum 50cm x 25cm x 18mm (they can be bigger because you'll cut off the excess with the jigsaw anyway)
I actually found from making a couple of sets of rings that cutting these sheets in half (to 25cm x 25cm) is handier when clamping..you get better contact with the clamps all around the circles, but you also need more clamps, or have to to one at a time.
- Apply Glue liberally to one of the sheets, don't be shy, it's not expensive.
- Sandwich the other sheet to it and clamp the Bejeesus out of it. As you can see I use all the clamps I could get my hands on including Quick-Grips, Vice grips and an actual Vice.
-Just make sure there's no gap between the plywood sheets and leave it somewhere for the glue to dry overnight or however long it says on the bottle.
Note: The plywood in the photos is bigger than 50cm x 25 cm so don't worry if yours looks smaller. I also drew my circles on beforehand. it doesn't matter when you do this.
Step 3: Draw Some Circles!
Internal radius: 90mm
Thickness of ring: 28mm
So when your glue is dry (or before you stick the sheets together) take your compass and draw 2 sets of circles as shown below, 1 set for each ring.
- The inside and outside lines show you where to cut and sand to and will be the dimensions of the rings AT THE WIDEST POINT.
- The Middle line is a guide for sanding so you know where the widest point of the ring will be. This is only on one side obviously but you get a good idea of the other side when you sand down to the lines.
I'd recommend going over these lines with a marker so they're easier to see, or if you can fit a marker in your compass, all the better! They'll all be sanded off eventually anyway!
Step 4: Jigsaw Them Circles!
Clamp the wood to something solid to make it easier to cut. The jigsaw might wanna shake around otherwise.
You should have 2 solid circles of plywood, looking like the photo below.
Step 5: Inside Circle!
When done, pop the middle out and you should have a rough pair of rings, like shown.
Now the easy bit's over, let's get stuck into the skill of sanding!
Step 6: Sand Them Baby's!
You can see from my photo below that the purple lines I drew on were done by hand over the pencil lines from the compass. They're a bit squiggly.
I recommend using a thin dark marker for these. Less room for error on the lines!
So clamp your ring to something..if you have a vice, perfect, otherwise just clamp it to a bench or other solid surface.
Sand in sections, you can kinda do the top half before moving it in the vice, and then the bottom half.
You want the outside edge of the ring to be perpendicular to the side..i.e. a right-angle and as flat as you can make it.
This ensures the ring is as circular as you can make it at the widest point.
Do Not Rush Any Of This. This part needs time and care to be taken. If you take a big chunk out of the side with the sander, you may have to start again.
Use one side of the sander as shown in the 3rd photo. I used the left side as I was sanding from left to right. Both for the inside and the outside of the rings.
Keep your strokes smooth and keep checking the lines. Use your hand to feel if it's smooth and circular. If it doesn't look or feel circular, then fix it.
It's very hard to get a perfect circle by hand but I've made 2 sets so far and by 2nd set were WAY better than the first. Don't lose hope, be patient!
Step 7: Get Your Curve On!
You want a circle cross-section when you're finished so remember this when sanding each 'corner'.
it's hard to explain but you should end up with a profie shape like in Photo 2.
Again, take it slow and keep feeling and looking at what you've done. Look down along the curve (the view in Photo 2) and see where needs extra sanding and shaping.
NOTE: Because the ring is now 36mm thick, you will need to sand the outside of both sides to reduce it to 28mm. I sanded the curve into it first and then sanded off a 'ply' of the timber on each side.you'll need to re-sand the curve as the side will be flat.
Another option is to use a belt sander or something to sand the whole ring to 28mm thick before you start sanding the curves. It's pretty easy to know how much you've sanded off using the layers of ply as a guide.
When that's done, do the other side and you should have something like Photo 3. I've left a slight high-point in the middle, when I sand it off, it'll take the marker with it and it'll be round. Again to get it really circular, you'll need to look and feel.
After this, do the inside curves, these can be trickier, trying to fit the sander inside and be able to move it. I tried to curve the sanding head of my sander to help it fit easier. if it's flat you might accidentally sand grooves where you don't want em.
Step 8: DaDaa!
Grab yourself some roofrack straps or ratchet straps and put them up anywhere...a tree, shed rafters, wherever!
try and find rated straps as the last thing you want when doing a muscle up is for your straps to break leaving you falling to the concrete on your back..Oww!
I don't know the forces exerted when doing muscle-ups etc but I'd be safe and guess 4 or 5 times bodyweight, so 5 x 80kg = 400kg
that's roughly 4kN but I'd get higher if available. Heavy duty ratchet straps will do too but they can be heavy and slow to adjust. Something quick and tidy work better if you're carrying them in yer bag!
Saying that, I've been using unrated straps without incident. Just be careful.