Ese defecto empezó a resultar molesto y peligroso, a tal punto que me vi obligado a interrumpir otros proyectos para construir un reductor de velocidad. Comprar uno está fuera de consideración, porque no solo son muy caros, sino que además el trabajo de adaptarlo a mis necesidades sería tan grande como construir uno. Evalué distintas alternativas, y como era de esperarse me decidí por la más fácil, que es la que muestro a continuación. No tengo fotos de todos los pasos intermedios porque la idea fue caminando a tientas, sin la seguridad que brinda el seguir un rumbo prefijado. Además, algunos pasos son obvios y no requieren explicación.
Este reductor se puede aplicar a muchos usos, no solo a un torno como el mío, de otra manera no valdría la pena publicarlo.
My "poor man's lathe" has a few flaws. Of course, if it were perfect it would not be "poor's" One is that, as it use as motor a hand drill, whose speed is variable but in too high values (1900-2500 rpm), sometimes does not help. Especially when the turning piece begins as a wood somewhat bulky and misshapen. If under these conditions it start to spin at 1900 rpm, can be a disaster because everything is shaken due to the imbalance.
This defect began to be annoying and dangerous, to the point that I was forced to stop other projects to build a speed reducer. Buying one is out of consideration, because they are not only expensive but also the work to adapt it to my needs would be so great as to build one. Evaluated alternatives, and as expected I chose the easier, which is what I show below. I don't have pictures of all the intermediate steps because the idea was groping, without the security provided by following a default course. Besides, some steps are obvious and require no explanation.
This reducer can be applied to many uses, not just one round like mine, otherwise not worth publishing.
Step 1: Nuevo Hogar Para El Taladro (new Home for the Drill)
The first step was to rescue from the bottom of a drawer a chuck into disuse. Luckily I could find it. I took him to the location where it could be secured on the lathe, and found that it was feasible. I started to build a new support for the drill, moved back to coincide the tip of its chuck whith the trunk of the chuck I mentioned earlier.
Step 2: Nueva Vida Para El Viejo Mandril (new Life for the Old Chuck)
I went to the industrial supply of the neighborhood and bought a steel bolt, 12 mm in diameter with threaded that screw in the recovered chuck, and a nut. I spent 5 pesos (U$S 1.25). Then bore a piece of hard wood to pass the screw through the center, and lathed the wood to the diameter of the drill support. Finally I adjusted the hole as best I could to the diameter of the screw, supplementing it with strips of aluminum sheets that belonged to a deodorant spray. With a little prodding was quite fair. I lubed it with lithium grease. The nut I bought was too high, and I cut it into two parts for use one as a counter nut, so that the screw is firmly secured to the mandrel, functioning as the axle.
Step 3: La Polea Grande (the Bigger Pulley)
From a piece of MDF (MDF) of 18 mm thickness I cut an annulus-shaped pulley. The inner hole is 1 mm larger than the diameter of the mandrel, so that its outer body can rotate freely inside the pulley. I screwed on one side a piece of iron sheet with a central hole, diameter of the screw-axis of the mandrel. Then tightly secured the assembling with the counter nut to the chuck body. I gave two coats of sealant made with white glue and water in equal parts, to increase the length of the MDF.
Step 4: La Polea Chica (the Smaller Pulley)
As that I need is to greatly reduce the speed, the smaller the pulley, the more effective. So I chose to use as such the stem of a screw. But It turns out that this is extremely slippery, so I had to cover it with sand paper, attached with latex adhesive (Poxi-ran type)
Step 5: La Correa (the Belt)
My son's dog spent a time at home, destroying some things including the nylon leash with which they walked. But it was a length more or less intact, long enough to serve as belt. I took the measure, cut, and using a piece of iron heated to the gas burner, I melted both ends tightly them together.
Step 6: La Manivela (the Crank)
To hand rotate the mandrel, it should have a crank. To this purpose I soldered to the head of the screw-shaft a piece of threaded rod to hold the crank. And for this to hold on to the screw, soldered an hexagon of iron sheet to a washer. Then I cut a small piece of iron dipstick, I made a longitudinal cut at one end and separated at an angle both sides before weld them to the hexagon. At the other end made a hole of 5 mm in diameter, which thread to put a screw nut for the purpose of putting on a little rotating handle.
Step 7: Conclusi�n (conclusion)
The reductor is certainly effective, but it may be insufficient for certain tasks. In this case I will have the recourse of intercalate an intermediate stage, ie a pair of coaxial joint pulleys, one larger than the other, so further reducing the speed. Meanwhile I'll use it as it is. The video shows it running.