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Los reductores de velocidad son al mismo tiempo, y por una cuestión física, aumentadores de fuerza.

Desde hace un tiempo yo tenía ganas de hacer un reductor a tornillo. Cuando decidí colgar del techo mi torno, estuve a punto de concretar el proyecto, pero finalmente, dado el peligro que representaba un peso elevado que eventualmente podría desplomarse en caso de falla, decidí comprar uno hecho, de esos que se usan para plegar y desplegar toldos metálicos.

Este tipo de reductor tiene varias características interesantes:
  • Permite con relativa facilidad obtener reducciones muy importantes, del orden de 100 a 1, o más. Eso es mucho más difícil de lograr con engranajes.
  • No necesita de una traba ni crique para mantenerse fijo en el lugar en que uno lo deja, porque al ser la reducción elevada y trabajar por fricción, el movimiento en sentido contrario es prácticamente imposible.
  • Requiere de un solo engranaje, en el cual encaja un tornillo o sinfín cuya rosca tenga el mismo paso que el engranaje.

Cuando comencé a construir mi chulengo (próximamente subiré el instructable) decidí que era una buena oportunidad para hacer un reductor de ese tipo, dado que la fuerza necesaria no era tan elevada como para que una falla pudiera ser desastrosa.


Speed reducers are at the same time, and a for a physical law, force enhancers.

For some time I wanted to make a screw-gear reductor. When I decided to hang my lathe at the ceiling, I was about to do it, but ultimately, given the danger of a heavy weight that could eventually collapse in case of failure, I decided to buy one made, the kind that are used to fold and unfold metal awnings.

This type of reductors has several interesting features:

  • Relatively easily allows to obtain very substantial reductions in the order of 100 to 1, or more. That's much more difficult to achieve with gear.
  • No need for a lock or crick to stay fixed in place when one leaves it, because being high reduction and working by friction, the movement by itself in the opposite direction is almost impossible.
  • Requires a single gear, which fits a screw or worm screw which has the same pitch as the gear.

When I started building my chulengo (instructable coming soon) decided it was a good opportunity to do such a reductor because the forces were not so high that a failure could be disastrous.

Step 1: Getting the Materials (conseguir Los Materiales)

Busqué y hallé entre mis cosas un viejo piñón trasero de bicicleta, desarmado, de 16 dientes. Había sido descartado por desgaste, pero para mi necesidad eso es superfluo. También hallé un trozo de hierro redondo de unos 7 mm de diámetro, y de largo más que suficiente.


I looked among my things and found an old bicycle rear sprocket, disassembled, 16 teeth. It had been discarded for wear, but for my need that is superfluous. Also found a piece of round iron of about 7 mm in diameter and long more than enough.

Step 2: Making the Shaft to the Gear (haciendo El Eje Para El Engranaje)

Soldé dos bujes concéntricos al engranaje para adecuar su diámetro al caño de hierro que recibiría el movimiento. Tuve cuidado de que el conjunto quede medianamente centrado.


I soldered two concentric bushings to the gear to match their diameter to iron pipe that will receive movement. I took care of the gear is fairly centered.

Step 3: Doing the Screw Thread (haciendo La Rosca Del Tornillo)

Enrollé en frío el hierro de 8 mm alrededor de otro trozo de hierro, de 12 mm de diámetro. En la primera etapa no me preocupé de conservar el paso adecuado, eso lo hice una vez que hube generado dos vueltas de lo que luego sería la "rosca" del tornillo. Como eje de este usé un trozo de dirección de auto, también descartado por desgaste. Monté ajustadamente las dos vueltas del alambre de 8 mm sobre este eje, de aproximadamente 13 mm de diámetro. Luego separé las espiras mediante un cortafierro usado como cuña, a efectos de que la separación entre espiras coincidiera con la distancia entre dientes.

Según mis consideraciones, con una vuelta y unos pocos milímetros más hubiera sido suficiente, pero decidí hacer algo más de dos vueltas, para que la fuerza quedara distribuida sobre dos dientes del engranaje. Creo que fue una buena decisión.


Cold rolled 8 mm iron around another piece of iron, 12 mm in diameter. In the first stage I did not care to retain the right step, I did that once I had created two laps of what would become the "thread" of the screw. As heart of this I used a piece of car steering, also ruled out through attrition. Tightly mounted two turns of wire on this axis 8 mm, approximately 13 mm in diameter. Then separated the coils by a chisel used as a wedge, to the effect that the separation between turns coincide with the distance between gear's teeth.

According to my observations, with a lap and a few millimeters would be sufficient, but I decided to do something more than two turns, so that the force remain distributed over two sprockets. I think it was a good decision.

Step 4: Welding the Thread to Axis (soldando La Rosca Al Eje)

Apliqué 4 puntos de soldadura: uno en cada extremo de la "rosca" y dos entre medio. No es necesario más, porque como explique antes, no va a haber fuerzas elevadas. Luego hice un ojal con el mismo hierro de 8 mm y lo soldé en la punta del eje, para que sirva de actuador.


Applied 4 tack welds: one at each end of the "thread" and two in between. It is not necessary anymore, because as explained before, there will be no high forces. Then made an eyelet with the same 8 mm iron and soldered it on the end of the shaft, to serve as actuator.

Step 5: Making the Support for the Screw (haciendo El Soporte Para El Tornillo)

No pude conseguir entre mis cosas un caño que sirviera como buje, así que corté dos trozos del más parecido que encontré, les hice sendos cortes longitudinales y los cerré alrededor del eje del tornillo y soldé los bordes de la unión. Monté provisoriamente sobre el eje los bujes improvisados y les soldé sendos soportes de hierro para poder montarlos en su lugar.


I could not get among my things a pipe to serve as a hub, so I cut two pieces of the closest tube I found, made longitudinal cuttings and closed them around the shaft of the screw and soldered the edges of the joint. Temporarily mounted on the axle these improvised hubs and soldered them two separate iron brackets to mount in place.

Step 6: Assembling and Testing All (armando Todo Y Probando)

Monté el engranaje de bicicleta sobre el caño que debe mover (su eje), y luego monté el tornillo con sus bujes de manera que la rosca calce en los dientes del engranaje.


I put the bike gear on the pipe that it should move (its axis), and then mounted the screw with its bushings so that the screw threads fits into the gear teeth.

Step 7: Recalculating ...(recalculando...)

La primera prueba resultó un poco frustrante, debido a dos circunstancias concurrentes:
  • La chapa del tambor donde estaban montados los soportes cedía ligeramente al hacer girar el tornillo, y entonces se perdía la buena relación entre el tornillo y el engranaje
  • Los dientes del engranaje tenían el borde demasiado filoso y se clavaban en el hierro del tornillo.


The first test was a bit frustrating, because of two concurrent circumstances:
  • The sheet of the drum where the brackets were mounted yielded slightly when turning the screw, and then lose the good relationship between the screw and gear
  • Gear teeth were too sharp edge and is fixed on the iron of the screw.

Step 8: Successful Test (prueba Exitosa)

Superar ambos inconvenientes fue relativamente sencillo. Por un lado, soldé una varilla de hierro que unía los bujes y los aseguraba al soporte del engranaje, haciendo un cuerpo más robusto. Por otro lado, con la amoladora de mano modifiqué el perfil de los dientes para que asentaran más amigablemente sobre la superficie del tornillo.

Una vez hechos esos ajustes, y corregidos algunos pequeños defectos de la rosca, el reductor funcionó perfectamente.


Overcome both problems was relatively easy. On one hand, an iron rod soldered linking bushings and secured to the gear support, making a more robust body. On the other hand, with the hand grinder modified the profile of the teeth to settle more friendly on the screw's surface.

After these adjustments, and corrected some minor flaws of the thread, the reductor worked perfectly.
<p>buenisimo - excellent</p>
<p>Gracias, Carlos.</p>
Your idea pleases me on realization of cochlear transmission. I thank.
Glad you like it!
So. I do with times something in my house so surely me oneself this idea will add.
!Rueda para tornillo sin fin enrolle en frio el hierro de 8 mm! !Excellent! <br> <br>Una pregunta por favor: ?por el rueda para tornillo sin fin, es enrolle en fr&Atilde;&shy;o el hierro mejor que enrolle en caliente el hierro? <br> <br>No tengo torno ni m&Atilde;&iexcl;quina de soldar, lastima. !Tal ves quando yo tendre mas anos! <br> <br>Tu&acirc;€™ amigo, <br>Bill <br>
Hola Bill! <br><br>Creo que en caliente se har&iacute;a mejor, pero tuve pereza de encender la fragua. Siendo una varilla no tan gruesa, lo pude hacer en fr&iacute;o sin problemas. <br><br>Hi Bill!<br><br>I think it would be best hot, but I was too lazy to fire the forge. Being a rod not so thick, I could do it in cold without problems.
Gracias, Osvaldo. <br> <br>No tenia la intelligence, solo la persistence ser un engineer. <br> <br>Tambien me gusta la astronom&Atilde;&shy;a.
No recuerdo si te cont&eacute; que mis primeros a&ntilde;os de Universidad fueron en astronom&iacute;a. Pero fue demasiado para m&iacute;, abandon&eacute; luego de 3 a&ntilde;os.<br><br>I don't remember if I told you that my first college years were in astronomy. But it was too much for me, I left after 3 years.
Buen trabajo
Gracias!
Wow, this is pretty amazing! I sell gearboxes and worm gearing at my job, so it's really cool to see your home made version.
Thanks for your comment. The worm gear reductors are expensive here. I think there wil be the same.
Nicely done. <br> I had an Idea to use one of those corkscrew dog anchors as a worm gear and cut the ring gear from a disk of plywood. purchased the tie out, but have never made it.
Thanks for your comment. this idea was thought by me during some years, but never I decided until this month.
Great minds transcend ALL barriers. Great Instructable!
Thanks for your kind comment. You make me blush, all we the great men are humble...
Genial! Me encanta la manera en cual hiciste las roscas.
Gracias, Bill! <br><br>Realmente fue muy f&aacute;cil hacerlo. Esta noche estreno el chulengo, donde el reductor tiene la funci&oacute;n de subir y bajar la parrilla. Espero que no se rompa en mitad del asado.<br><br>Thanks, Bill!<br><br>It was really easy. Tonight I will release the chulengo, where the gear serves to raise and lower the grill. I hope that will not break in the middle of the roast.
Excellent technique! Wonderful idea.
Glad you find it useful, thanks for your comment.
You made your own screw drive. I would have looked and looked for one. Congratulations.
Thanks, Phil. <br> <br>Must I change the tittle to &quot;Screw drive&quot;?
The usual name would probably be a worm gear drive. I do not know that you need to change the title. It is clear enough.
I would know this as a worm screw, worm drive, screw gear, screw drive and a few others<br> <br> I don't think it will really matter as the men in sheds who follow Rimrar's posts will know what the subject is about anyway.<br> <br> Here is what Wiki says <a href="http://en.wikipedia.org/wiki/Worm_gear" rel="nofollow">worm gear</a> its quite interesting and worth having a look.
Very interesting article. I forgot the guitar tuner, it is worm-gear drive too.
Genious! Thank you so much for showing us this beautiful technique.
Thank you, no big deal. You make me blush, all we the great men are humble...
That is seriously impressive, building your own worm screw.<br> <br> I would&nbsp; have just gone for the easy option of buy this or taking the worm screw from something else.<br> <br> <a href="http://en.wikipedia.org/wiki/Isambard_Kingdom_Brunel" rel="nofollow">Brunel</a> would be proud of you.
You hand fabricated a worm gear! <br> <br>There is only one thing to say and that is &quot;we're not worthy&quot; lol :-)
Thanks, Dr Qui!
Neat, I like drive transfers like this. <br /> <br />Do you use this to lower your lathe, if so what do you use to power the gear to the screw? If not what do you hand-crank (screw) to the gear?
Thanks, Mike.<br> <br> No, to hang my lathe I bought a commercial one, of those <a href="https://www.google.com.ar/search?q=polifuncional&oe=utf-8&rls=org.mozilla:es-ES:official&client=firefox-beta&um=1&ie=UTF-8&hl=es&tbm=isch&source=og&sa=N&tab=wi&ei=pIaeT-yFCIXe9AS07qyODw&biw=960&bih=488&sei=qIaeT_LbLZGE8QTrppn3Dw#um=1&hl=es&client=firefox-beta&rls=org.mozilla:es-ES%3Aofficial&tbm=isch&sa=1&q=m%C3%A1quina+toldos&oq=m%C3%A1quina+toldos&aq=f&aqi=&aql=&gs_nf=1&gs_l=img.3...15971.19792.2.20711.14.12.0.0.0.0.824.6174.3-1j0j4j4.9.0.bI2MYx0Ho-k&pbx=1&bav=on.2,or.r_gc.r_pw.r_qf.,cf.osb&fp=f4a0cd7c91fe07f5&biw=960&bih=488" rel="nofollow">used to operate metalic awnings</a>.
To operate both screw drives I use a <a href="http://img1.mlstatic.com/s_MLA_v_O_f_81602959_8005.jpg" rel="nofollow">manual crank handle</a>.
Nice work. I love it.
Thanks, cammers. I had fun doing it, and seeing that it works acceptably.

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