Magnificent - with apologies to Jill & Stan’s daughter
(a shot of the upper wheel covering for Al)
Stan arrived during the holidays with a bright and shiny white box, some wire, testing tools, a laptop and and a hair dryer. Everything made sense but the hair dryer.
We mounted the VFD to the wood clad steel column behind the bandsaw and then started with the wiring. Everything made sense until Stan wired the hair dryer and placed it on top of the bandsaw table. He said it was to test the brake. Sure enough - when he cut the power - the hair dryer started up. He asked me to check to see if there was warm (or hot) air coming out of it. No - not really. Hmm he said. Fired up the laptop and started reading.
Now I have to admit - I was completely out of my element here. My very basic understanding of VFD’s came from Stan the week before. I had no clue what the hair dryer was really doing - but it sounded like a clever cross-check to me.
There was a blade on the saw now, so we had a real-world set-up. We took some readings as we started and stopped the machine. We delayed the start up to 6 seconds to lower the start up draw and then focused on the brake time. Stan was reading furiously and changing things on the VFD and every time we turned it off - the hair dryer would come on. But not always in the same way. One time, it came on with such force that it launched itself backwards and almost into the path of the slowing blade. That could have ended badly. Another time, it gave a bright red blast of really hot air.
There was something more to this hair dryer than I was aware of. So I asked. Stan said that he had looked into braking capacitors and they were at least several hundred dollars for a suitable one. As he was pondering the function of the brake capacitor he realized a hair dryer could accomplish the same thing. So he ‘borrowed’ his daughters hair dryer (checked the Ohm’s), to test it out.
Stan was not quite sure what was happening and checked the specs printed on the hair dryer. He asked if we had one and if we could use it. I said sure, ran into the house and grabbed the dryer. He wired it up and turned on the bandsaw. When he killed the power, the new hair dryer blasted red hot, sparked, and then gave a last breath of smoke. It was cooked. There was a pursing of lips, then a slight smile and a knowing nod. Not a word was spoken and the other hair dryer was hooked up again.
All the adjustments he was making to the VFD had to do with controlling the manner in which the brake was applied. The feedback was the hair dryer’s response. It was at this point that Stan commented; “I am not sure if the hair dryer will fit with your aesthetic or not.” This is the point where I fully appreciated the situation - the hair dryer was the brake capacitor!
I just smiled a slow smile as this all sunk in. Are you kidding me - your daughters hair dryer as a vital part of the Y30 - this is going to be wicked! I told him I would have no problem with it - there would be a way to make it look good.
In Stan’s words - here is what is happening;
“The hair dryer is working as a braking resistor. When given the command to slow down, the VFD turns the motor into a generator and the kinetic energy in the bandsaw wheels is converted into electricity, and then heat by the blow dryer.”
The ideal situation was for the hair dryer to come on for several seconds as the bandsaw stopped. That would indicate that it was functioning properly and dispersing the heat. After some further tinkering, We had the blow dryer running for several seconds and the bandsaw stopped within 13 seconds. The hair dryer came on with an even blast of heat - not red hot, and not a strong blast. We had found the sweet spot.
It was at this point that Jill came into the shop, hair wet and asked if I knew where the hair dryer was. Stan and I looked down at the dead dryer on the shop floor. It was all we could do not to burst into laughter. I explained the situation quickly followed with, “I will pay for a new hair dryer”.
It was getting late in the day and we were out the door to go for dinner with some friends, so Stan packed up and left me to wire up the on/off switch and deal with the hair dryer.
The next morning, I got up early, excited to finish the installation. It was too early to go to the hardware store to get a surface mounted electrical box - so I decided to work on the hair dryer. I made a plywood mounting bracket and placed the dryer just above the VFD.
We had taped the switch in the on position.
Onto the low voltage switch. Stan has said a light switch would be sufficient, but I was a little worried about it accidentally being bumped on or off. A push button switch made more sense to me. As we have been renovating our house, we have been replacing the original push button switches with ones that are up to code. So I called my electrician to see if he thought I could use one of the old push button switches from the house. He reminded me that every woodworking machine must have a magnetic switch (so if the machine is running and the power goes off and then comes on again - the machine will stay off). The VFD is a magnetic switch so I was covered that way - and he thought the old switch would be perfectly good.
It felt pretty neat to be re-using one of the old switches on the bandsaw - somehow the 100 year old brass plate seemed like a much more suitable solution than a plastic or galvanized plate.
Here is a quick shot of the VFD with the dryer.
One of the other things Stan and I tested was the amperage draw as the saw was cutting. Stan asked if I had a large piece of scrap wood to test it with. I handed him a large piece of scrap cherry (several inches thick) and he shoved it through the saw faster than I have ever cut anything in my life! At full running speed, the saw was drawing 5 amps and the needle barely moved as he slammed the wood through.
I have been using the saw for almost a week now and I have to say - so far, it is exceeding my expectations in every way. The first real work I did with it was cutting the perimeter of a chair seat. This is something I could not have done with my Laguna bandsaw - the table is not large enough to support the 20" seat and there is not enough room for the seat to fit between the blade and the column. And the cutting action is completely different. It is a little hard to explain really. It is incredibly smooth, there is no vibration to the table at all and even the sound is different. The blade tracks perfectly, cuts perfectly and seems to be taunting me with “is that all you got little man?” All I have to say is the 10" thick rosewood is coming soon enough.