Here is how I assembled a secure platform for Barney’s biking cage. This is just an example that has worked well, and held up in like new condition for more than 2800 miles to date. When completed your cage platform should look like the picture below. Click on the images for a more detailed view.
Step 1: The first thing to do is to make sure that the platform and it’s mount will not interfere with the brake and shift levers or the cables that run from them to the components. Determine the amount of rise above the handlebar that you will need, this is accommodated by the top bracket you will make from the two 24 inch pieces of aluminum stock. When mounted to the handlebar the top brackets should be six to eight inches apart and centered about the fork stem.
Step 2: Measure 1/2 inch from one end of each of the 24 inch pieces of aluminum stock and mark a centered position. This will be the position of one of the U bolt holes. Hold a handlebar U bolt to the aluminum stock and also mark the location of the inward hole you will need. Carefully drill a suitable hole for each of the U bolt ends in each piece of the 24 inch aluminum stock.
When you are all finished the handlebar mount will attach as in the image above. Loosely attach the two pieces to the handlebar at the handlebar locations you have chosen, having them point straight up. Use your sharpie to mark the point at which you will need to bend the upper brackets to avoid the shifters and cables. Carefully make a 90 degree bend at the mark that you have made. Do not bend them too sharply so that the metal is not stressed. It is very important that they are bent at the same location and radius or your platform will not be level from left to right.
Have someone assist you in holding the front wheel straight forward, and the bike vertical. Attache the top brackets that you made so that the horizontal portions are level, check with a bubble level and tighten the U bolts when they are positioned correctly.
Step 3; Use a saw to cut a 24 inch section of your 1 inch by 12 inch pine board. Position the board over your upper brackets with the rear of the board about an inch or so in front of the bracket bend and centered left ro right on the upper bracket arms. Have someone hold the bracket arms and board, note that the arms may not be exactly parallel due to the angles of the handlebar but you will need to position them so that thee front and rear of the bracket is at least an inch from the left and right edge of the board so that it can be attached and not crack. Trace the arm position with a sharpie on the bottom of your board. Note that the board will extend beyond the front of the upper brackets. Remove the board and the brackets from the bike.
Step 4: On a flat surface that is drill safe but the board bottom side up, and place the upper bracket arms you have made in the traces from the sharpie in step 3 above. The bends should be pointing up. Drill four appropriate sized holes for your bolts thru the aluminum right thru the wood. The front holes should be about 1 inch from the aluminum ends, and the rear ones about two inches from the rear end of the board.
Step 5: Place a washer on two of your shorter bolts, insert the bolts from the top of your platform thru the rear two holes in the board and thru the bracket pieces and hand tighten so that all four holes line up. Re-attach the upper bracket and board to the handlebar.
Step 6: Drill a 1/4 inch hole through the fork stem as shown in the picture below.
Step 7: This may be the most difficult step as you will be making some interesting bends. The quality of the work that you do in this step will affect the positioning and security of the cage platform. Look that the picture above and the one below to see how things should end up when finished.
Take a look at the picture of the bottom bolt and you will see that the bends are at an angle both along the length of the piece, and the radius due to the fact that one end of the supports are at the same point and the other ends are about eight inches apart. In addition, since they are on top of each other, the position of the bends is different so that they can nest in each other. The goal here is to have a level platform when you are finished. I would suggest that you make the bottom bends first, then hold the supports under the platform to determine where you need to make the top bends, then mark and bend those.
Trim the excess material from the front of the support arms. I used a piece of that to go across the front of the board so that vibration will never crack the board.
Step 8: Now that you have your bends, hold the pieces in place with the platform level, and mark the positions of your mounting holes. Drill the holes and use the longer 3 inch bolt to hold the bottom, and the two remaining 2 inch bolts to secure the front. When finished the bottom should look like the picture below.
And the top should look like this.
Now that the platform is assembled, carefully tighten all of the nuts so that the platform is secure. Recheck the nuts after a few rides to make sure all is well, and of course check as you maintain the bike.
Next, the cage