The Craftmans Shop > New from Old
Dominion Supreme Elliot Universal Woodworker
awemawson:
That series of photographs really ended too soon, as after they were taken I designed and built a 'DC Injection Brake' circuit for each of the motors.
DC Injection Braking, as it's name implies, is a way of stopping a motor much faster than it normally would by coasting to a stop. My aim was to have the spindles stopped within 3 seconds of the stop button being pressed. The planer and the table saw without braking would spin for several minutes !
So how is it implemented: In essence it is simple. Three phase power is removed from the motor, and DC from a separate source is 'injected' into one of the three phase windings. That simplicity is deceptive. For obvious reasons the circuitry must absolutely ensure that it is impossible to put both the three phase AC and the DC on at the same time.
My circuit monitors the three phase power to the motor, detects when it ceases, triggers a 'dead band' timer the end point of which fires a second timer controlling the DC injection via a contactor. The AC three phase and DC contactors are also interlinked so only one can be on at once. By varying the voltage of the DC source and by varying the time setting for the second timer the 'time to stop' can be adjusted. There is also an interlink to prevent the user trying to restart during the stopping time.
To keep things simple I created three separate DC supplies. It would be perfectly possible not only to share the supplies but generate the DC from a thyristor source off the mains. However I wanted to make a circuit that worked reliably without months of 'development' which I succeeded in doing.
Meldonmech:
Hi
What a brilliant machine, like a Rolls Royce and so compact, I would have really enjoyed restoring that machine and how rewarding that must have been. I have individual light trade machines and they take up more room than your universal. There is not much timber construction you cannot attempt with that sort of capacity. What sort of things have you made? You were lucky with the spares.
Well Done David
dsquire:
Andrew
That is the type of machine I would have loved to have had. You can work them all day and they have the capacity to do so many things if properly fitted out. I can imagine how much enjoyment you get from rebuilding/restoring these machines and then being able to use them to trim out your house. :clap: :clap:
Thanks so much for sharing this one with us. That is the beauty of MadModder, it doesn't have to be metal working machinery to fit in. :D :D
Cheers :beer:
Don
awemawson:
--- Quote from: Meldonmech on September 03, 2013, 01:54:13 PM ---Hi
What a brilliant machine, like a Rolls Royce and so compact, I would have really enjoyed restoring that machine and how rewarding that must have been. I have individual light trade machines and they take up more room than your universal. There is not much timber construction you cannot attempt with that sort of capacity. What sort of things have you made? You were lucky with the spares.
Well Done David
--- End quote ---
Thanks David.
The machine has been put to lots of use on structural timbers in the house re-built. Luckily it came with a tungsten carbide tipped rip saw as lots of the oak we pulled out has returned in a different form. Various beams have been re-sized. Rebates cut etc. One of it's most impressive tasks was a new pair of rustic beams in our drawing room. This room was formed from what was originally two rooms. The ceiling heights were different and one wall was not in line with the other forming a step. We managed to get a HUGE chunk of oak, complete with genuine woodworm holes, from an old barn, and split it down the middle so that the weathered / rustic sides were exposed and the new cuts to the wall. End result is you'd not know it wasn't original.
awemawson:
--- Quote from: dsquire on September 03, 2013, 01:56:28 PM ---Andrew
That is the type of machine I would have loved to have had. You can work them all day and they have the capacity to do so many things if properly fitted out. I can imagine how much enjoyment you get from rebuilding/restoring these machines and then being able to use them to trim out your house. :clap: :clap:
Thanks so much for sharing this one with us. That is the beauty of MadModder, it doesn't have to be metal working machinery to fit in. :D :D
Cheers :beer:
Don
--- End quote ---
Don yes there is something very satisfying using a machine that is up to the task. My woodwork shop is only ten foot wide, so it was a bit of a squeeze getting it in. Might need to build an extension, as I have a 24" re-saw sitting under a tarpaulin on the barn loading dock that is awaiting a rebuild then SOMEHOW squeezing into the already over filled woodwork shop. This shop has (mentally going round the wall) A DeWalt site saw on long tripod stand, a pillar drill, a Union Graduate wood lathe, a disk sander, a massive Chain Morticer with hollow mortice as well, a separate Sedgewick hollow morticer, a Viceroy Sharpedge plane and chisel sharpener and of course the Dominion along with two floor mounted cupboards and three dust extractors! There IS no more room.
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