Normally any hoop larger in diameter than about 25" (or approx. 65cm) will begin to flex. A large KIB hoop 35" in diameter flexes so much in can be called a "bounce". This bridge style brace reduces the flexing to almost zero or to very minimal depending on the size. The length of the handle can also be a factor.
A closer look at how the bridge style brace is assembled using 1/2" CPVC fittings and 1/2" PEX tubing material for the hoop.
A completed KIB hoop 35" in diameter with 1/2" PEX tubing and a bridge type brace to drastically reduce flexing. All CPVC pieces are attached using CPVC cement exclusively.
The top 1/2" CPVC cross bar piece is 15 1/2" across for the 35" diameter hoop and has the wooden dowel piece inserted. The smaller 25" diameter hoop has a cross bar of 10 1/2" across.
A 15" long 1/2" diameter wooden dowel piece is inserted into the CPVC cross piece tubing for added support. I coated the dowel piece with white carpenter's glue to prevent any possible rattling in case the fit was not perfect.
Close up detail of how to assemble the handle attachment piece
Further example of the assembly of the bridge design. Note that the bottom 3 CPVC "T" pieces are 3/4" with a reduced 1/2" center port used only for the 35" diamter hoop using 1/2" PEX tubing. For the smaller 25" diameter hoop 1/2 "T" pieces are adequate. IMPORTANT: The angles for the bottom 3 "T"'s need to be correct suited to the size hoop you are making. It is best to mock up the final design of the entire hoop before you make any permanent attachments.
File the threads just enough so the 3/4" CPVC threaded piece will snugly fit over it
In order to further strengthen the handle attachment I increased the threaded piece from 1/2" to 3/4" by first filing off the threads of the 1/2" threaded piece (as shown)
....as shown. This will now allow you to fit a stronger length of 3/4" diam. CPVC tubing for the 35" diameter hoops. For the smaller 25" diameter hoops a handle made with 1/2" CPVC tubing reinforced with wooden doweling works well.
1/2" diam. PEX tubing is used for the hoop and is inserted through all 3/4" "T" pieces. Short 3/4" PEX tube pieces are inserted into the T's as sleeves which reduces the T diameter to 1/2" for a more snug fit. The 1/2" PEX tubing fits nicely inside the 3/4" PEX sleeve pieces as shown.
...same for the right hand side
The left side of the T (to the left of the bridge) has a longer sleeve piece as shown. For smaller diameter hoops 1/2" "T" pieces work well and the shims are not necessary.
I used the appropriate size fine threaded machine nuts and bolts to firmly attached the pieces together that could not be glued
Left side, right side....
Also, the 45 degree piece needs to be bolted also as this is a location of high stress.
The hoop is spliced together at the very top of the hoop opposite the bridge.
The completed Large 35" diameter KIB hoop with minimal flexing suitable to fit almost any adult (or two).
I used a short 3" dowel piece that works just fine. There are many other options that work as well.
To connect the CPVC fittings to each other you need to cut 3/4" pieces from a 1/2" tube section of CPVC. If you don't have a cutter or utility knife a hacksaw will do.
3 different KIB hoops. The smaller 25" diameter hoop has almost ZERO flexing. The 35" diameter hoop made with 1/2" PEX tubing has minimal flexing and the 35" diameter hoop made with 3/4" PEX tubing has nearly ZERO flexing.
Press the connector piece glue end inside the fitting for a permanent bond exactly as shown.
Apply the CPVC cement as shown ...