There is a steel or stainless steel plate on the bottom of the sander which is called 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.I wonder what's under this thingy?
There is a steel or stainless steel plate on the bottom of the sander which is called 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.
Time to deal with the switch
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. I've decided that this must not happen to our sander so either the switch needs to be taped down, or the switch must go.
All gone!
The switch is now off and it occurs to me, "If you're going to hardwire 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? Look at all that extra wire!
Switch gone, cord gone. Next we connect the pigtail to the motor wires.
Fuzzy pic, but you get the idea
The wires and wire nuts are tucked nicely in place, and the cord is anchored with a little plastic bracket.
A little tape and we're done
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. This is starting to look good. Oops! This photo is out of order! More on that next.How do you mount a common pulley on a 10mm left hand threaded shaft?
You can't, that's how. Off to the shop with some 1/2" steel rod and a few minutes later we have two new shafts. The lower shaft that originally had the large pulley had a M10 shaft with a right hand thread, so that one is easy. The left hand thread just wasn't going to happen with the time that I have left so desperate times called for desperate action. I drilled a 9mm hole and using the sander's own motor, filing the threads down just a hair made two parts that were just a smidgen shy of fitting. Perfect. Smear a little high-strength epoxy on what remained of the threads and with a hammer the shaft was driven home. We checked the O.D. of the shaft and it didn't bulge a bit. We'll let the epoxy set for a few hours before messing with the pulleys.Why is it that I can never find a tap wrench unless I don't need it?
Thank you Mr. Grip for your wonderful invention! Just in case you're wondering, no, I didn't turn the lathe on during this step. It does make a nice bench vice for just such an occasion.30 minutes is long enough, isn't it?
Here are the new pulleys in place on the new shaft extensions. Looks good. Now, where can I find a 17 5/8" long v-belt?Anyone?
Bueller?
Got my drive belt
After confirming at a local belt/pulley/bearing shop that the belt I needed was not a stock size and that a link belt made sense, it was off to Woodcraft. The bearing house had this belt too, but I just didn't think I needed 200 feet of it! I figured that 24 links would be just about right, but just in case I purchased 4 feet. I linked 24 links together and "Ta-Da!" it's just about perfect!
Gotta choose a sanding belt next... but how?
I recalled an article in Fine Woodworking in which they compared the effectiveness of several random orbit sanders using an clever method. They weighed identical boards before and after sanding for an equal amount of time. I figured that this method could be modified for this purpose so off to the shop we go. I started by cutting and then weighing identical sized pieces of plywood. I chose ply because it looks like this is what Accuride used for their track. My thinking is the belt that 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.
So many belts, so little time
Here's a view of the progress mid-test. I had 11 different belts from my favorite manufacturer, Carborundum. These belts featured Aluminum Oxide, Silicon Carbide, Zirconia Alumina, and Ceramic abrasive.
How were the tests run and what did we learn?
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 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 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.Which one won? I'm not telling! At least not until after the race.
Test over and you can still see my plaid shirt
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?
How about this for a body?
I'm still not sure how we're going to make this happen, but the body of the hydroplane in this photo is what I have in mind for our sander “body”. I don’t think ours will be three-dimensional, but I like the looks of this.
Sander is loaded into track and ready for second race.
Our sander is in the track and ready for its third race. This photo shows the CVS one-time-use video camera mounted on the body. This race was against Louis & Co. See video for the results of this race.
Click the pic to Biggie-Size it, and stop staring at my belly!
Here's a view of the bottom of the racer's "Body"
The built of the body went so fast that I forgot to snap photos! Here’s a good picture for any of you who want to know more about how you can build your own racing sander. From this view you can see the rollers that are mounted to the bottom of the "body" which helped to keep the sander centered in the track. 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, loosing momentum with every bump. The rollers I used are part of a very simple sliding door system from Häfele, part # 404.32.951 and were quickly screwed to the bottom of the body. Well, that’s not exactly accurate. Daniel and I took a hacksaw to them to remove a couple superfluous metal thingies, but other than that it was a simple solution.
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Belt Sander Racer Confession #1: I Upgraded the Platen
6/9/09 In the post titled "I wonder what's under this thingy" 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 magicians 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 beeves that this single upgrade gave me an advantage over most sander in the field.
Belt Sander Racer Confession #2: I Swapped the Pulleys
At the last second (in the pits no less) I wound-up switching the large pulley for a smaller one. The big one shown here was very fast, but it caused the sander to accelerate very slowly. If the race lasted 10 seconds or more this wouldn't be a problem, but in the end we broke the 3 second barrier, so I guess we made the correct choice. I left the photo of the large pulley on the blog because it was the only one I had at the time, plus that whole misdirection thing.
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