I've made them before, both flat and coned shaped to fit certain rims.
You'll want to use cardboard as a template to figure out exactly how big you need to make your covers.
If it is coned shaped, you'll need to either tape the cover on both sides where the cut is to the center of the cover.
Or, you can use glue to seal the seam for a cleaner look.
In the case for moped wheels (I'm guessing you're using the Tomos drum brake wheels) all you need is the diameter for the center of the wheel at the widest point and the inner diameter near the bead.
This way all you'll need (if it is five spokes) then you need zip-ties or something similar to keep them on.
I've got templates for the Tomas wheels, assuming they are the same type of wheel as I've see before I can get you the dimensions for the covers.
I have used .040" polystyrene sheets and they came out pretty well. What didn't work was using 6 button head Allen screws to retain them to the wheel. Apparently that doesn't spread the load out enough because the plastic started to tear around the screws and I had to take one of the inside covers off midway through the second heat of the first race I used them in.
Archer, could you try cutting down the outside diameter of the disc cover to fit the inside part of the rim? Mine snap into place because of the step on the inside diameter of the rim. The inside disc on the front wheels I have tape holding them in place to have them clear the disc brake caliper.
As far as I know, Mike Hodgert uses zip ties to keep the covers on and in place. You'll want to do them wide enough (towards the outer diameter edge of the disc) to prevent the covers from flapping due to bumps in the road or the wind.
It really depends on if you want to take them off in case of access to spokes, etc.
My first set of covers for my previous wheels were smaller and were retained with heavy duty foil tape. However I found that by the end of a race the tape was starting to tear and the one of the inside covers was able to rotate all the way around held on only by the brake rotor.
For my next set I'm considering the screw technique with an adhesive all the way around the edge of the rim.
I just covered a wheel with two layers of heat-shrink tape like what is used when shrink wrapping a boat. Easy enough to do. It remains to be seen how well it holds up but it seems sturdy enough.
Zaine if you wouldn't mine what are the dimensions you use on your wheel covers for the Tomos moped drum brake wheels? Also you said you use cardboard for making the template but what material do you use for the final wheel cover. Thanks
You'll need to make two covers for it to work.
Inside wheel cover is 15.125" diameter for outer diameter. Inside near drum is 4.8125" diameter for the inside diameter.
Outside wheel cover is 15.125" diameter for outer diameter. Inside near axle is 4.0625" diameter for the inside diameter.
That should make the covers lay flat pretty well on the rims.
Typically these can be attached with zip ties on the five spokes between the inside and outside diameters of each cover.
Should prevent them from rattling around but now allow them to flap due to wind.
The material I was using I believe was HDPE M/M Opaque Sheets.