I haven’t updated the thread in a while but that’s because there really hasn’t been much to show, I’ve just been pottering about getting finish on stuff and tinkering with the seemingly endless list of little jobs to do. Well nothing to see until now!
This weekend was really productive, I finally got a blade on this yoke!! As you can see, everything has had a few coats of oil based poly, the wheels balanced, the 14” bicycle inner tubes stretched over the wheels (that was a struggle but at least I don’t need to worry about them falling off!) and the guide blocks cut out of an old lignum vitae crown green bowling ball (that stuff is so hard, I never want to have to do that again!).
As planned I balanced the wheels using a couple of small bearings mounted on a long bolt. I started this trying to be scientific, placing small pieces of MDF on the top of the wheel until it was balanced, measuring them, calculating the moment based upon the radius to the edge of the wheel, then calculating the volume of material to be removed from the wheel at a lesser radius yet maintain an equal moment, use this volume divided by the CSA of a 35mm Forstner bit to determine the depth to drill to. In reality it was easier to just drill a bit out and check the balance, removing more as required.
So anyway once that saga was concluded I could finally get a blade on this thing! A few checks with a straight edge showed that I needed to use a few 2mm shim washers behind the wheels to get them lined up, I’d bought a dozen or so, just in case. I got the blade tensioned and the tracking in the centre of the wheel but when rotated in reverse it wandered backwards slightly, so off with the blade, loosen some screws and shift the lower shaft over a couple of mm. No maths, just blind luck and the blade now stays in position regardless of direction of rotation.
Next I marked up the blades position in relation to the frame and cut the notch that holds the upper guide post. A quick trip to Toolstation saw me in possession of a tube of epoxy which duly squirted into a hole in the frame fixed a piece of threaded rod which the post clamp screws on to. Guide post on and it looks pretty well lined up but I’m not exactly enamoured with this design, the frame is softwood, my workshop is unheated and a bit damp so I think this needs some adjustability. I’ll have a think and see what I can come up with.
So the blade is on, guides are sort of done, I’ve extended the frame a little at the rear to take the motor, not bad for a morning. At this point I decided that I’d had enough of kneeling on the cold concrete floor so I turned my attention to a base for this contraption. Measuring the height of the beams in the workshop determined the height so I got to it breaking down some sheets of MDF I’ve had knocking about, I’ll give all this a few coats of paint to protect it from the aforementioned evil damp but I’ve got a bit of flushing up, filling and sanding to do before then. The base has some cunningly hidden pieces of Baltic birch plywood in there to provide strong anchorage for castors and the frame holding down bolts. No idea what I’m going to keep in the drawer yet but as I’m sure you can tell from the tip, storage is always welcome in my workshop!
A final note, I think this is where a lot of builds will stall as I am approaching the point where I will have to start leaving the plans behind and apply my engineering brain to get this working properly. All those tiny inaccuracies when making each component seem to have a habit of adding up, resulting in little misalignments. To fix this I will have to do a lot of very frustrating fiddling.
