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Old 06-02-2010, 07:40 PM   #9
paul.miner
Knee Dragger
 
Join Date: May 2009
Location: Wichita, KS
Posts: 738

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The cases are a little large, external dimensions are 19.78" x 15.77" x 7.41". The width at the rear of the bike is a little under 36", an inch wider than my mirrors.

I don't have a detailed parts list, but it'd probably be something you'd need to customize for your bike. I can go through some of the considerations that went into it though.

First, I wanted luggage style cases that I could lock to the bike, but easily remove and carry off. I didn't want the lock to be directly preventing the case from being removed from the bike since I thought this would put too much load on the lock. I ended up with a design where the luggage rests on rails with tabs that prevent it from being lifted straight up, and the lock only preventing the case from sliding side-to-side.

I also wanted to mount them far back enough that I could still carry a passenger. I had my girlfriend sit on the back while I held the cases up to figure out where to mount them. It worked out pretty well, as the cases don't even touch her. The muffler was another consideration, and was a large factor in how far out the cases had to be from the bike. My muffler is carbon fiber though, so heat was not a big issue other than at the tip where the exhaust gases exit. Had heat been more of an issue, I think a metal plate mounted to the frame and not touching the cases would have helped.

Most of the frame is just 3/4" angle steel, bolted to the rear subframe. The "hoop" part that the luggage attaches to is 3/4" square tube steel. The catches/tabs on the hoop and on the luggage are aluminum, for a couple reasons. The main reason is that I didn't want to have the catches/tabs rust together. Another thing I later noticed is that angle steel does not have a clean 90 degree bend on the inside, it has a little extra material that webs between the two halves of the angle. Aluminum angle has a sharp inner corner which meshes together with other corners better.

The angle steel bolted to the subframe is 1", but only to accommodate the larger bolts used there. Something to consider is that wherever you need a bolt, you need to have enough clearance for a wrench and/or socket. Similarly, having bolts too close to each other can make it difficult or impossible to get a socket on one bolt if both bolts are in. Whenever I bolted two pieces of angle steel together, I put the two outsides surfaces of the steel together. Because of the little web of material on the inside of the angle, mating an outside surface to an inside surface would be flush unless I ground some of the "web" out (I did have to do this a couple times to get extra clearance for bolt heads and washers though). Adhering to this way of bolting the angle iron together worked out pretty well though.

Using angle steel helps eliminate the need for bracing in some areas, and makes it easy to bolt some members to each other if you don't have access to a welder. Bracing I used flat steel, but the angle iron was useful in most places.

The basic element that the luggage mounts on is the hoop, the rectangular steel shape that the luggage rests on. Since the hoop needs to be held at a distance from the bike due to the fairing, there are two vertical posts bolted to the rear subframe that hang below the fairing, and four angle steels that connect them to the hoop. I opted to weld much of it together, but I could have bolted them together as well. Had I bolted them, I would have added some extra diagonals to stiffen the structure.

Since the hoops are basically hanging from the rear subframe, another important piece is something running between the two sides/hoops to resist forces pushing in on them. I had a straight bar running between them, but had clearance issues with it and the rear wheel. I ended up welding a braced support that was mounted higher but improved rear wheel clearance:



Ideally, I could have had some U-channel aluminum to make the catches/tabs from, but the only U-channel I could find at Lowe's was edge trim, which was quite thin and not very deep. Instead, I used various pieces of aluminum angle bolted together to create U-channel. The important thing was to countersink the holes so that the machine screw heads would not scrape along the sliding surfaces. Here's a closer look at the latches/tabs.

First, the case sitting on the rail:



Then, the case is slid along the rail, sliding the tab on the case under the catch bolted to the hoop frame:



On the bottom rail, a patio lock (like a deadbolt) bolted to the case slides through holes drilled in the tab, catch, and hoop frame. I had to put it on the bottom rail because there wasn't enough space on the case above the top rail to bolt the lock. I also had to make sure to bolt it high enough that the deadbolt did not hit the bolt running through the hoop frame.



When I assembled it, I didn't leave any extra clearance to allow it to slide smoothly (1/8" thick aluminum tab sliding under a 1/8" catch), and it was about impossible to move. I also made the tabs 1", when they really only needed to be about 3/4" to accommodate the deadbolt (or even less for the other tabs). I ended up taking a prybar to each catch to open them up a bit, and a grinder and file to every catch and tab to ease the transition of sliding the tab into the catch. Rounding off the corners would make it nicer when bringing it into a tent

There were a few protrusions on the back of the case that I had to grind flat. I also shimmed out the hardware I attached to the case with 1/8" aluminum, to create a gap between the catches on the rail and the side of the case (visible in the pictures of the catches/tabs). If you bolt the hoop together, anything sticking out needs to clear the case as well.

On the inside of the cases, I used small 1/8" aluminum plates (this is the only thing I didn't buy at Lowe's, I picked the plate up at The Yard Store). They basically served as giant washers to distribute the load of the bolts over a larger area. The size of the flat surface on the inside of the case will determine how large the hoop can be. I made mine a little smaller so I had some room to play with when mounting the case hardware. I could even have angled the cases differently from the hoop (I would have if it wasn't for the exhaust limiting how much I could soften the angle).

Because you need something on the inside of the case to bolt to, it's important to start with figuring roughly how much room you have on the inside to bolt hardware, and then determining the size of the hoop and where to locate the catches based on that. Remember that there needs to be enough of a clear spot on the rail for the case hardware to slide. I put the catches on the low side (towards the front of the bike), so that it the case+tabs natural want to slide down the rail into it. This also keeps the deadbolt from binding.

I still haven't decided what I'm going to do to cover up the nuts/bolts on the inside of the case, but I don't think this will be a big deal. Maybe just stick some foam over it.

For reference, the catch in the first picture is made of 1" x 1/8" aluminum angle for the larger part, and 3/4" x 1/8" aluminum for the smaller part that creates the gap for the tab to slide into. The two bolts running through them hold them on the hoop.

The tab bolted to the case is made of the same two aluminum angle pieces, but of different lengths. The 1" piece is bolted to the case through a 1/8" shim with the same footprint, using four countersunk machine screws. The 3/4" piece is bolted to the 1" piece with two small machine screws. The heads are countersunk so that they don't rub the rail. I used screws of size #8, and lock washers to help them from spinning off. I'm satisfied with it, so I'm going to go back and locktite everything pretty soon.

Sorry that was so long, but there were a surprising number of little things that went into this. If you have any questions, feel free to ask!

Last edited by paul.miner; 06-02-2010 at 07:42 PM..
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