Introduction: Build a WINNING Belt Sander Drag Racer
I've had a secret desire to get involved in belt sander drag racing ever since reading a back cover article in Fine Woodworking Magazine many years ago on Belt Sander Racing, so when one of my coworker's encouraged me to get into a race at the AWFS woodworking show in Las Vegas in 2007, it didn't take much prodding.
In these events the sanders speed down a 75 foot-long track side-by-side and stop (theoretically) when they impact a bumper at the end of the track. At the race in 2007 this sander left the end of the track TWICE, including one INCREDIBLE flight where it launched over the head of several track officials, and was snatched out of the air by my pit crew; Mr. Daniel Tripp!
Fortunately this moment was documented on video, which can be viewed in Step 14!
Anyway, I'm a bit surprised at how little information there is about this is on the web. There are a few videos on Youtube, but other than that I've been unable to locate any "build sites" or blogs besides mine. So in the interest of posterity and the advancement of the craft I will share with you almost everything that we learn along the way. I say ALMOST everything, because the competitor in me still wants to have a little advantage on race day! I make one promise: I will not provide inaccurate information. This can't be said for a few competitors who I've spoken with, who have tried to send me down the garden path with downright deception. I'll share all that I can and will remain silent on the rest. Fair enough?
The ladies in the photo worked very hard during the event by returning the extension cords to the center of the track between each race. Upon seeing this photo my wife’s first comment was “Nice sleeves”. Followed immediately by “No play for Mr. Grey”.
Thank you for your support, Hon.
If you are going to be at the AWFS show in Las Vegas this Summer be sure to bring your fastest sander and I'll give ya a run for your money!
One last note before we get started. I've entered this Instructable in the "Epilog Challenge" contest here on Instructables and am supposed to say a few words about what I would do with the top prize if I were to win. The prize is a Epilog Zing laser cutter, which is something I've dreamed about for years! I'm an active woodworker and Horologist (Clockmaker) who loves to make jigs, fixtures and tools, as well as anything else that sounds interesting. Heck, just take a look at my eclectic Instructables! I would love to have a laser for several projects that I've had in my head and on paper for years, including a neat little kitchen slide-rule that can be used to quickly modify recipe quantities.
Here's a video of the race at AWFS 2007. The first one ends with a shot of my sander as it took flight.
Check the last step for more great videos!
Step 1: First Things First, We Need a Sander
Here's a photo of the foundation of our racer: A Makita 9403, which I snagged on Amazon for a great price. My research uncovered that this sander is the fastest stock sander, with 1650fpm (feet per minute). That fact alone makes this a great choice if you are racing in the Stock Class. Seeing that the track is 75' long, and for simplicity let's just figure that it reaches full speed instantaneously, (I wish) that means that this sander theoretically could cover that distance in 2.2 seconds. Now, obviously it will have to build-up to full speed, and there will be some time loss due to slippage between the belt and the track and even between the belt and the drive roller, but this is still a good start.
There are some major modifications ahead, but first let's lighten this sucker of any unnecessary parts...
Step 2: I'm Torn Over Whether to Disclose This Idea or Not...
I guess in the interest of promoting the art of racing I'll go ahead and share this idea. I'm sure I'm not the first to think of this, but I've never seen it discussed. We're about to remove the exhaust fan. Why? Well, let me ask you this; Why do we need it? We aren't really sanding anything, and as I see it, it's just offering resistance. Seeing how these races last all of 2.5-3 seconds every fraction of a second counts, and this part just isn't needed. The cover came off with four screws.
The white plastic part looks like a diverter or seal that retains and funnels the dust into the dust bag. I've never looked into this part of a sander before so it's kind of cool to see the path that the dust follows from the rear roller through the fan and into the bag. Simple and clever. I like it and now it must go! This part just lifted right off. It was held in place by pressure from the cast metal side of the sander.
The fan was attached with a single screw and washer. The screw was easy to remove, but I needed to hold the fan stationary with one hand while loosening the screw.
The fan lifted right off. I don't know much this amputation is going to help, but I figure it's not going to hurt.
Step 3: Let's Take a Look Under the Hood
With only a single screw to hold it in place, the belt cover was calling to me to be opened, so of course I had to oblige. If you take a look you"ll notice that this photo was obviously staged because the small pulley is shown slightly loose on it's shaft. It looked like the quick fix to speeding this bad boy up would be a quick swap of the two pulleys, but when is anything worth doing ever simple?
The belt is a toothed or cogged belt, which means it's going to have to go. Why? Well, at the speeds that we're shooting for a cogged belt will be ripped to shreds, and believe it or not we need to accommodate a "little" slip between the belt and the pulley upon start-up, so as I said, the toothed belt was bad news.
Step 4: Even a Little Pulley Can Teach a Big Lesson
- It pays to take your time thinking about how tools are made and the forces that are at play. This shaft turns counter-clockwise and therefore must have left-hand threads.
- If this one has left-hand threads then the large shaft must have a right-hand thread. Crud! So much for my first thought about simply swapping the two pulleys. Oh yeah, I'm going to use a poly-v belt so I have to replace the pulleys anyway. (I've got to get more sleep!)
Step 5: Time for a Bagectomy
Step 6: The Front Knob Is Held in Place With Two Screws
Not only is the knob extra weight, but the two threaded holes should be a great place to anchor parts of the body.
Body? What body? Perhaps I'm being to generous with that term.
The sander will need "something" to keep it centered in the 12" wide track, and until I decide what method to use I choose to think of this as the body of the racer. Trust me, if I'm going to the trouble of removing something as light as this knob I'm not about to replace it with a heavy body. I believe that style or theme is a portion of the competition, so whatever we do it needs to add something to the sander's character.
I really like the design of hydroplane boats, so my sander emulates one. But I digress...
Step 7: Still a Few More Parts to Investigate
The rear roller is what is called the drive roller, and it's spinning on a pair of ball bearings. The front roller is a mystery, so I thought it was worth taking a look to see if there was anything to improve there.
The axle is held in place with a single snap-ring, which was easily removed with a cleverly named tool called snap-ring pliers.
I stopped by Harbor Freight and picked-up a set of snap ring pliers. They have a belt sander that's a dead-ringer for my Makita on sale for $20! Why am I going through this learning curve with a $200+ sander? Because that's the way I roll, that's why.
I picked-up a set of the pliers from Harbor Freight for under $7 and it's been surprising how many times they've been called into action. Back to the sander...
Before we dig into the front roller I've got to tell you that I'm surprised by how poorly this roller idles. What I mean is when you have the belt off and you spin the roller it grinds to a stop after about two rotations. I suspect that I know why this is, but we'll know for sure in just a few seconds.
The snap ring was opened and the axle slipped free and landed on the table with a sudden "THUD" that caught me completely off guard! For some reason I expected to have to drive the axle free, but obviously it's just held lightly in place.
The second photo shows the axle slipping easily our of the sander, and the third photo shows the view from the end of the roller.
Beneath the steel washer in the background is a pair of bronze bushings. That explains why the roller idled so poorly. What to do now? I suppose I could polish the axle and do some investigative work to find the best lubricant, or perhaps I should press in a ball bearing. Press it in where? Oh yeah, there's nowhere to press a bearing into.
OK, so do I turn a new roller all together with accommodations for bearings? (Sigh)
One thing that I know from previous tool experience is that until they begin to wear, well-lubricated bushings are low-drag, so I decided to polish the axle on both ends where the bearing rides and add some fresh oil and re-assemble the roller back onto the sander.
The last photo shows the front roller and the axle, as well as the mount on the front of the sander. In this picture you can see the axle has a polished end only . This is because the bushing doesn't run the entire length of the roller and the axle is turned a bit thinner in the center to reduce the area making contact with the bushing. In fact, there are two bushings, one at each end of the roller. I suppose if you must use bushings that this is the way to do it, but if I was going to use this sander for actual sanding I can see how this would become a maintenance nightmare. The axle was quite oily and I'm sure it would be a dust magnet, so I wiped it clean and added a dry lubricant.
Step 8: What About the Bottom?
The bottom of the sander sports a polished steel or stainless steel plate that is known as the platen. The platen is a flat surface that backs-up the sanding belt and without a firm or semi-firm platen, the belt can't create a flat surface. In this case the platen is backed-up by a cork backer, which is common. Below the cork is a waffle-like casting, which makes sense. Had this been a solid surface it would have been difficult for Makita to grind it flat due to warping caused by the heat of grinding. By making this waffle-like they can easily grind it flat, and the cork will smooth out the surface of the platen. Nice work Makita.
The thought occurred to me that perhaps this should get some paste wax or some other type of lube; but that thought quickly passed when I thought it completely through. Any lubrication on the platen would quickly transfer to the abrasive belt, and in turn to the rubber-coated drive roller; causing slippage, or loss of power to the abrasive belt. This wouldn't be a good thing, but perhaps this is something I should suggest to my opponents? :-)
When I posted the information above on my build-blog I went into a bunch of detail about the stainless steel platen on the bottom of the sander. This was what magicians call misdirection. It's why they use pretty assistants!
That information in that post was true, but during the actual race I didn't use the stock platen. Nope, I was aware that an upgrade existed that would make the belt slip like Vaseline on a door knob, and that is the Porter-Cable 48119 Graphite Impregnated Sanding Shoe. Though this part wasn't made for my sander, it took almost no modification. I did have to trip 1/8" off with a pair of scissors, but that was it. I believe that this single upgrade gave me an advantage over most sander in the field, and now I share it with you.
Use this little secret only for good, Grasshopper.
Time to move on.
Step 9: What Else Can We Learn?
We might as well call this step "What Not To Do"! I just couldn't stop myself from opening the motor compartment to see if there was anything else I could remove or supe-up.
The black plastic cover slipped right off exposing the field magnet, which is actually two strong electromagnets. The black plastic cover appears to be a dust cover. I guess I'll leave this on too. Man, I'm really getting lenient in my old age.
It just took two screws and a tug on the casting and I was staring into the belly of the beast. The bad news was as I was gutting this pig I heard a loud "CLICK" and my heart sank. I forgot about the brushes! Yep, there they are. I now need to remove the brushes because the commutator won't slip past the brushes now that they have been driven inward by their springs.
What's a commutator you ask? The commutator is the part that the brushes rub against in order to energize the motor. It's all very interesting and if this is new to you check out HowStuffWorks for an explanation. Just make sure you click the "Next" button to see the animation.
Anyway, you can see that the carbon portion of the brush is long and intact, so these will work fine for hundreds of hours, or 288,000 races!
The next photo shows a fan that I had to fight the urge to remove! Even though a 2 second race isn't going to cause the sander to overheat. I can't see this little fan slowing the sander down by a measurable amount, so for now, it stays.
Step 10: The Switch Must Go, and We'll Shorten the Cord While We're at It
Not too sure what to do with what I find in the handle, but I have to take a look.
This is odd. The wire that leads from the switch to the motor is a lighter gauge than the wire in the cord. That can probably be improved. I also didn't like the way the cord is pointed up and above the handle, so we'll relocate it below the switch somehow.
As I review the videos on Youtube I noticed several sanders pop a bit of a wheelie at the start of the race, and having the cord lower may lower the center of gravity a tad. Additionally if the cord hits a snag during the race having it lower might keep it from tipping up.
I've seen three videos online where a sander failed to start off the line because the "Driver" didn't lock the trigger into the on position. This must not happen to our sander so either the switch needs to be taped down, or the switch must go. Yep, it must go!
The switch is now off and it occurs to me, "If you're going to hard-wire the cord, why are you using the entire 8' cord?" Hey, I'm right. The extra cord will just take more amperage, so why not convert it to a pigtail?
The wires and wire nuts are tucked nicely in place, and the cord is anchored with a little plastic bracket.
The cord still concerned me that it was anchored so high on the handle, so a few rounds with the tape and the cord is fixed nicely to the handle.
Step 11: It's Time for the Real MODS!
The first picture on this step show the results of this step; which are new pulleys in place on new shaft extensions.
To make the shafts I cut two short lengths of a 1/2" diameter soft steel rod that I knew would match the stock pulleys that I would purchase. I chucked them one at a time into a machinist lathe and after measuring the motor shaft, I learned that not only was it a left-hand thread, but it was metric to boot! I drilled the shaft and tapped it with the correct tap, which I purchased from our local Granger branch.
Fortunately the lower shaft had a right-hand thread, and I happened to have the proper metric tap on hand. What I didn't have was a tap wrench, so rather than leave the shop you can see that I took matters into my own hands and grabbed a pair of Vise Grips.
One last thought on this step. It was obvious that the new belt wold be an odd size, so I purchased a length of link belt from my local Woodcraft store, which I knew I could make to whatever length I needed. On top of the custom-ability, link belts transfer power very efficiently, so it's a win-win.
Step 12: The "MODs" Are Done, But There Is Still More to Learn
If you've ever watched a NASCAR or INDY race you know how important the tires are. It seemed logical to me that my belt choice was just as critical to the success of my sander. Sanding belts are available in countless grits (levels of coarseness) and in dozens of minerals as well as man-made abrasives. How do I choose which one is best?
I recalled an article in Fine Woodworking Magazine where they compared the effectiveness of several random orbit disc sanders using an clever method: They weighed identical boards before and after sanding an equal amount of time. I figured that this method could be modified for this purpose so off to the shop we went.
I started by cutting and then weighing identical sized pieces of plywood. I chose ply because it looked like this is what the sponsor of the race used for their track. My thinking was that the belt which removes the most wood in the allotted time would be my winner. Good idea? I don't know, but it's all I've got.
One of the photos shows the progress mid-test. I gathered 11 different belts from belts that featured Aluminum Oxide, Silicon Carbide, Zirconia Alumina, and Ceramic abrasives.
Each belt was mounted on the sander and run in mid-air under no load for ten seconds to allow the belt to flex and stretch a bit. Tracking (How straight the belt runs on the sander) was also adjusted and then the sander, running at full speed, was brought into contact with the board for 10 seconds. The sander was held loosely in one hand and was allowed to slide gently from side to side about 1/2 inch to keep the paper from clogging. As you can see from the third photo the sander is leaning left due to the poor balance brought on by the new heavy pulleys and arbors.
The boards and the belts were numbered to keep everything in organized. From here the boards were re-weighed. The weird thing is all but one belt removed .2oz's, but that one magical belt removed .3oz's. That doesn't sound like much but it's 50% more than all the others. I re-tested this belt and sure enough, .3oz's again. I have my belt!
By the way, the belt used on the board above is not the winner.
With a massive combined total of 2 whole minutes of sanding, I was shocked to see how many places on and under my clothes were covered in swarf ! (That's sanding dust you know) Fun test.
Now, what's next and why are my eyes burning?
Step 13: Time for a Body
The built of the body went so fast that I forgot to snap photos during the process! I did do a quick concept drawing and I've also added a good picture of the finished sander.
The second photo was taken by a spectator at the moment the sander accidentally launched off the end of the track. One good thing about this view is you can get a good look at the rollers that keep it centered on the track.
On that note, several sanders at the BSRA race at the AWFS show simply ran their sanders down the track with only drive train modifications. Their sanders may have been fast, but they bounced from one side of the track to the other the entire length of the race, losing momentum with every bump. The rollers I used are sliding door wheels like those found in any hardware store and were quickly screwed to the bottom of the body.
One final note on the body. I debated the idea of centering the sander in the body, but decided to mount it as far back as I could. This would add weight on the front end which I hoped would keep the sander from popping a wheelie. You can see from the photo that I removed so much of the body to accommodate the handle that I actually had to add a rear "bumper" made from a decorative cabinet door handle to keep the body together.
I added another of these handles on the front of the body, and it's a good thing too, because this bumper really "bumped" when my sander rolled off the track on one of the first runs! Yes, this sander was so fast that it left the track on two runs!
The front bumper tore off on the first impact with the floor, so in the airborne photo you can see an on-the-fly mod with a couple strips of duct tape.
More on that in the last step.
Step 14: Gentlemen, Start Your Engines!
Here are a few more videos from the 2007 BSRA race.
And finally, we tried again in 2009, and that time we WAY overbuilt the sander body, slowing it WAY down!
This round was close, but we lost. I'll be back.
We have a be nice policy.
Please be positive and constructive.