A Day at the Belt Sander Races (w/video)
Every once in a while
madness an idea presents itself that’s so horrifically wrong, yet so clear and so elegant that even in spite of one’s vast experience and common sense, it’s irresistible. So it was with “A Sander Called Bruce”.
The New England Belt Sander Racing Association (NEBSRA) has been racing belt sanders at the Kenyon Woodworking shop for 27 years now, presumably since the first two guys cleared off the shop floor after a few beers on a Friday evening and settled once, and for all time, who’s badass belt sander was faster. It soon turned into an event, and as the story goes, next-door neighbor, Boston beer brewer Sam Adams jumped onboard early on, donating beer to help raise donations for local charities. In the words of one of the founders, Dave Kenyon, “We do it all for charity, because, frankly, it’s kind of hard to explain otherwise.” Thus, legends are born.
The races are broken into two categories – “Stock”, which must have no alterations to the original drivetrain, but may be adorned with all manner of decorative embellishment, and “Modified”, which has but one rule: The sander must be driven by sandpaper. Our team has entered several sanders in the distant past under the Modified class, but we’ve always been limited by one basic law of physics: the power to the sander can only be as much as the cord can deliver. That is, about 120VAC, 20A, and losses from the 100′ extension cord. Thus, our plan. Power the sander with an onboard energy-delivery system. AKA: batteries.
That’s a fine idea, and kept us amused for several long New England winter nights, and, as it does, the New England Belt Sander Races took a hiatus for several years. We were relatively safe. Then, a few months ago we heard the races were on once again, the date set for Nov. 1, the day after Halloween. “All Sanders Day”, as it shall be known. Then, this happened:
That, dear readers, is a legendary Briggs and Stratton ETEK axial flux, 10kw PMDC 23lb motor with the wheels from a mobility scooter found in the junk pike at the local dump. Er, “transfer station”. How could anything so wrong appear so easy? One thing led to another, and, with the addition of a RC lipo battery pack, a golf-cart contactor to control the power to the motor (on, and off – basic binary motor control) and an AC powered 48V power supply to control the contactor, “A Sander Called Bruce” was born. The math said it would do 0-60 quicker than a Tesla Model D.
After numerous test runs, it was clear that the maximum motor voltage of nearly 100VDC would simply be madness. We settled on the first tests at 50VDC, and even that spun the drive wheels so fast that the belts literally blew off the wheels from the force. We dialed it back to 36VDC, and even at that, it was clear we needed one addition – wheelie bars.
Only one thing was left. Choose a name. We felt that the sander pretty much spoke for itself, and after reviewing the numerous and creative suggestions from our Facebook fans (WYSIWYGrit, Pulp Friction, and Colonel SandASS some of the top contenders), we decided that “Bruce” spoke best to the unassuming character of the beast.
Here are the specs:
- Voltage: 36VDC
- LOA: 30″
- Width: 11.5″
- Power: 10kW
- Current: 400A +
- Weight: 60lbs
- Speed (calculated maximum): 120fps (85mph)
- Estimated ET for Standard Competition Belt Sander Racing Track (75′): 0.8 sec.
There was, however, one concern. It’s all good until some guy runs a 60lb power tool at 85mph in a crowded room full of drunk bystanders in a wood-framed building on the second floor with volatile battery chemistry and no idea of what this particular flavor of disaster might look like.
It was agreed that, discretion being the better part of valor, one demonstration run would be allowed with all possible precautions in place. It was further agreed that the operator would simply give the sander “a squirt” to see what happened. Somehow that “squirt” became “full power for over half the length of the track”, but such is the way with the vagaries of racing.
Without further ado, here’s the video:
The decision of the judges was immediate and conclusive. After a brief bout of uncontrolled laughter and hysterical giggling, the call was, “It’s just not fair”. Also: “We’re creating a new class, especially for you. ‘Unrestrained’.” And this:
Looking out the window on the 2nd of November, and the first snow of the season, a plan is already starting to form for increasing the traction, cutting the weight in half, and enhancing the impression of safety. We’ve also got a plan for using a combination of enormous electrolytic capacitors and a massive inductor from an unnamed source within the automotive EV industry for ramping up the voltage over the first .3 seconds to “feather” the torque delivery, and hold traction a little longer to allow the mass of the machine to start moving before getting full voltage. Tests for the actual coefficient of friction of grit ranges from 24 grit up to the currently accepted standard of 65 grit are being formulated. We like data, after all.
It may be a long, cold winter but there’s heat in the shop… and “Wait until next year” are words all too familiar up here in New England… the home of the Boston Red Sox.