A Riveting DIY project: replacing riveted race sled parts.
In the last Sled Tech article you got to hear me rant about sled care and maintenance and how summer time is a great time to do work on your sled. Well, summer is just about over, so it’s time to get to it. I know that not everyone is a DIY kind of person, but many of these projects are relatively simple and I aim to help folks out on some of the simpler concepts in the next few issues. This month we’ll go ahead and dive right into a DIY project on replacing sled parts that are attached with rivets.
In the past few years of sled repairs one of the jobs I get often and do not particularly enjoy is the replacement of race sled bed plastic that has been attached by rivets. On the farm as a boy, I remember helping my father do work on a cattle and horse trailer. My job was to replace parts held on by rivets and at age 10, I got my education on the joys of rivets. Don’t get me wrong, rivets are great connectors and there are lots of reasons that they work great for this application. They are made from aluminum, so they are light and mostly corrosion resistant. They are very strong and used heavily in aeronautics and boat building, so they have been tested extensively in higher stake technology where failure is not an option. If they keep boats floating and planes flying then they must be able to keep your sled sliding. They also have a very low profile, which is nice on the bed of sled so that they do not interfere with the payload and create wear on your sled bag.
The specific type of rivets typically used on dogsleds is the blind rivet known to some as a Pop rivet. It is called this due to the fact that one back side of the rivet can be hidden within the object. Blind rivets have a mandrel in the middle of the rivet assembly that is drawn into the rivet causing the blind end to expand and then the mandrel is broken loose. This expansion is what creates the fastening effect of the rivet as seen in Figure 1.
Figure 1. Illustration showing the expansion of a blind rivet. Copyright of http://www.marshallsales.com/pr_rivets.php
They are remarkably strong for their size and if used properly they create an almost unbreakable connection. This is where the problem lies. They outlive the bed plastic that they hold to the frame of the sled leaving you with a jagged mess of plastic being held tight by rivets (Figure 2). This can be very difficult to fix in the field.
If you have some time and some simple tools, fixing a sled bed like this can be relatively simple. While it seems like rivets are eternal grasping monsters, they can be overthrown easily with the use of a power drill and properly sized drill bit to drill them out. First determine the size of the shank of the rivet. You want your drill bit to be as close in size as possible without being bigger. Otherwise you will enlarge the hole in your metal parts and make it difficult to put new rivets back in the hole. Before you start drilling it is good time to take note of the direction in which all the rivets are going, which side the head is on, whether there are washers on the bottom sides, etc. Take note of what the original sled builder did since you are trying to reproduce that. I usually snap a bunch of pictures in case my brain forgets.
You will then drill into the top hole of the rivet until it cuts the head loose from the shank and the shank will fall or push out of the object it is holding (Figure 3). The rivet heads tend to stay on the drill bit and in my fits of drilling rage, I leave them and continue until my bit is full. The quickest and easiest way to remove them is by grabbing them with a vise grips or pliers and with the drill in reverse, back the bit right off of them and get back to drilling (Figure 4).
Figure 4. Use a vise grip or pliers to remove the rivet heads from your drill bit.
In the case of replacing a sled bed that has been riveted, you will want to remove all rivets. If the cracked bed is still in the proper shape it can be used as pattern for the new bed plastic, removing all rivets and attached parts will allow you to lay the old bed flat on the new bed for hole pattern.
When replacing bed plastic, make sure to get virgin UV protected ultra high molecular weight (UHMW). plastic. There are also recycled UHMW plastics which are ground up bits of UHMW that are re-combined to make new sheets. You can actually see the different colored plastic pieces in it. I try to stay away from that plastic and stick to virgin plastics with a UV protected formula. These newer plastics should outlast your old sled bed. You can stay with the thickness that the original sled builder used i.e. 1/8” or if you want a more indestructible sled you could go up to 1/4” thickness on your plastic.
UHMW is widely used plastic in factories, so finding a supplier in your area shouldn’t be difficult. Some suppliers will cut the plastic for you and sell you just what you need. If not, you may have to purchase it by the sheet. UHMW usually comes in 4×10 sheets. To cut your UHMW sheet you can use a table saw or cabinet saw if you have a nice big runout table that will support the entire sheet. If not, please stay away from the table saw. It can be very awkward trying to run floppy sheets through a table saw and pretty dangerous. I have done this and I DO NOT recommend it! Otherwise, you can use a circular saw with a big rip fence made from a super straight object such as 10’ of angle iron. Be cautious of using long pieces of wood that may be warped, leaving you with an untrue cut. My favorite method is to use a DeWalt Track saw. It is basically a plunging circular saw that runs on a specialized rip fence track.. giving me long straight cuts. I support the UHMW for cutting on a large work table or saw horses for cutting. Any woodworking saw blades will work, but I have found that crosscutting/finish blades with higher teeth counts give the cleanest cut. If the bed has any special shapes, you can use a jigsaw or a hole saw to get these once the main shape has been cut.
Figure 5. Use the old bed plastic as a pattern for transferring hole locations to the new bed.
Once you have the UHMW cut to the proper size it is time to mark out the rivet holes on the new bed plastic. You can get out your tape measure and marker if you like. Or if the old bed is held together enough to be accurate, you can clamp it to the new bed and either transfer the holes with a permanent fine tip marker, or you can use a center hole punch and hammer to tap the marks into the new plastic. In this case, I just clamped the old bed down securely on a piece of old plywood and drilled directly through the old bed holes into the new bed (Figure 5). The rear portion was cracked out badly leaving me with a few holes to measure out. Using the metal parts that were connected to the plastic, I transferred the remaining holes in the correct position. Make sure to use the proper size drill bit that matches the old holes (Figure 6).
Your drilling may have left rough edges around your new holes. Use a countersink bit to clean up and lightly chamfer the edges (Figure 7). Do not apply to much pressure or you may rip right through your UHMW and make a bigger mess out of it.
In order to rivet parts together you need rivets and a rivet gun of some sort. You can use a hand rivet gun, such as a Pop Rivet gun on the right or you can get fancy and use a pneumatic rivet gun on the left (Figure 8). If you only plan to do this once in your life you can get by with the hand tool. The childhood experience I spoke of before was with one of these rivet guns. I have done several sled bed replacements with one as well and it will make you have some amazing forearms or might just give you carpal tunnel. The pneumatic gun I have was relatively cheap (at $80) and makes this job more enjoyable and less painful.
Figure 8. Choose your weapon.. Pneumatic rivet gun on left and hand rivet gun on right.
When it comes to choosing the correct rivets for the job, you will want to figure out what the diameter of the shank of the old rivets was and get the same diameter. It is important to find the correct grip range of the rivet. Rivets are designed to be a little longer than the thickness of the items they will be holding together. If the rivet is too short, it will not hold securely. Measure the thickness of the items you will be connecting and find rivets with the appropriate grip range which will be marked on the container. Also when working with plastic, it is a good idea to find rivets with larger diameter heads to grip the plastic without tearing through. If your rivet bottoms will be expanding out directly on plastic instead of metal parts you will want to purchase the appropriately sized aluminum washers as well.
Now comes the riveting fun. Clamp your metal pieces to the plastic and commence riveting! Make sure that the rivets are pressed firmly in place and that the items you are riveting are held firmly together. Otherwise you may end up with a sloppy and loose rivet job. If you do, just drill out the rivet and start over. If the expanding part of the rivet is expanding in a metal hole, then no washer is needed (Figure 9). If the expanding portion is on plastic, make sure to apply a washer before riveting the items together.
Some of the riveted sleds have cross supports between the stanchions, some do not. If your sled has cross pieces it likely had little pieces of UHMW riveted on the bottom of the bed around these cross pieces to protect them from getting caught on things on the trail. Hopefully the old protectors are still in good shape, but likely they are not. If the old ones are destroyed you will want to make new ones. Making pieces to fit around the crosspieces requires a bit of heating and bending which is a whole other topic I will be covering in depth soon in another issue. Cut your pieces of UHMW to match the old ones. heat, bend and drill your holes to match. In the case of this sled, I was able to use the cross bar protector as a pattern to transfer rivet holes to my new piece . Riveting plastic to plastic, you will want to use the washers on the expanding side of the rivet. Otherwise it will just pull through the plastic and fall apart on down the trail.
When riveting the crossbar protectors to the bed, you may have a hard time lining up the holes. I use a couple small bolts, nuts and washers to pull the pieces together and hold them in position while I rivet the remaining holes, then I remove those bolts and rivet them together. Make sure your bed is attached to the rear stanchions and the front piece of the sled and anywhere else it was attached. In the case of this sled, it was riveted into the hollow center of the middle aluminum crosspiece and riveted to the front plate/brushbow piece, and then bolted to the rear bed support stanchion, holding it firmly to the sled frame. Once those are all attached, the sled is ready to roll (Figure 10).