Step 6: Speed Control (part 5 - Improving speed regulation and low speed torque)

If you're happy with that (slightly shoddy but workable) speed control setup you can skip the next two steps, however...

An optional further increase can be had in speed regulation and low speed torque by effectively converting the machine to a direct current shunt wound motor. To do this we rectify the speed controller output and supply the motor with DC (direct current). We also use a very low voltage (and high current) to energize the field coil.

As shown in the diagram, we still keep the 240V DC running through the field coil as well, this gives the benefit of reducing starting current surges. It is important to wire the two rectifiers such that they are pushing current in the same direction through the field coil (see diagram).

The transformer, being the most substantial electronic component is definitely worth scavenging (A new transformer is likely to set you back a good 15pounds). To our shame, in Britain at least, you will not have any trouble finding one. Likely places for the transformer are junked stereos, amplifiers, power supply boxes (though most wall warts are not up to it), and other electronic devices that routinely get thrown away.

To do this we will need the optional components mentioned earlier - a transformer (100VA should suffice - but see what you can find) and bridge rectifiers (these get quite hot, high current ones are a good idea). After flirting with the idea of using a rewound microwave transformer (and discarding it as overkill), I came across an old-school Spectrum power supply at the local tip (which is essentially a transformer with a rectifier and smoothing capacitor) - just the ticket! It is only rated (on the case) to 2.1A at 9V DC and I was needing more like 5A, but after testing it seemed the rectifying diodes were the weak link, and the transformer, when not completely sealed in plastic, as it was originally, actually runs nice and cool when delivering a steady 4.2A.
<p>Awesome job!<br><br>P.S.<br><br>I didn't know you can buy stuff from recycling points in UK...</p>
<p>Looks awesome!!!</p><p><strong><a href="http://www.rachelallan.com/prom-dresses/rachel-allan/2" rel="nofollow">Prom Dresses</a></strong></p><p><strong></strong></p>
<p>Maplin doesn't seem to carry the Suppressor diode (HW13P) any longer. Can you give details on it so I can find one that will work in it's place? </p>
Made a lathe from a 1750 rpm cap start motor. I decided not to have speed control or any belts/gears. Just connected the head piece right to the motor shaft. It works great for what I want.
<p>Sir since I live in the pacific islands there's lots of coconuts and I want to make a coconut meat grater using a discarded washing machine motor! can you help me with this project!?? almost the same as this lathe machine of yours but the wiring is too complicating! Please!!! just tell me what to do ! should I follow your rewiring of the motor you did!?? please need help!</p>
<p>very very brilliant gentleman thou art!! What a gift you have Sir and Im awed at your brilliance and good heart for sharing!! Be greatly blessed Sir and invent on! many thanks and many respect to you! Be blessed and stay blessed!!</p>
<p>one of the most impressive instructable on net. great work!</p>
<p>I like the ingenuity in this build!Being in the US,I have different voltage obviously.Do you know if the circuits you built would work for 110AC motors?</p>
Can you point me in the right direction for a speed control solution for a capacitor start ac motor?
<p>That's a hard one. Hopefully someone more knowledgeable will chime in, but if you are talking about single phase induction motors there are very limited options, the easiest and best usually being a mechanical solution using reduction pulleys or gears. If it's 3 phase you can use a variable frequency drive, which gives a great solution. </p>
Can't believe what I see on Inst' <br>Thanks for sharing and Congrats ++++
In case you are interested, aluminum (in vacuum) makes a better heatsink because of its emissivity at lower wavelengths of the IR spectrum. Stefan-Boltzman formula says that it is more black body like (emissivity is closer to 1), etc. <br> <br>Although, convection is more relevant here, so that point is kind of moot. I dunno of a good table to look at this because the convective heat transfer should depend intimately on the shape of the sink. Maybe someone else knows something about that.
First off: thanks for this well written Instructable. <br>Literally the same day as I read it, my parents washing machine broke down. Not ignoring that sign I started building my own, inspired by yours. <br>It works perfectly now and I didn't spend a single penny on it. <br> <br>As headstock consists of parts from an axle from a big trailer. Slightly overkill, but it works brilliantly and can definitely stands the forces. The tailstock is from a bike. <br>As rails I decided to go for pipes, since they were free. <br>The electronics is the only thing which differs from your design. It incorporates parts from the washing machine electronics. It has zero-phase detection for proper speed control. It can reverse, break, and dynamically adjusts the power. So it pumps more juice into the motor when it gets slower due to high loads, which makes it a smooth experience to work with and almost impossible to make it go slower when working intensely. Also, no transformer, so 230V all the way. <br> <br>The spindle is rather simple: everything needs to be screwed into place. I'm still looking for a proper spindle - for free of course. <br> <br>
That looks fantastic! Thanks for sharing!
Bongodrummer - are you an ex-Rhodie or South African? faffing around gives you away ou china.
Hello, I have been wanting to build my own lathe too. I have viewed your steps and they are very helpful! I do have a taper bearing I found laying around in my toolbox. How would I go about mounting/using it? It's just the bearing, no cap or housing or anything. Still works nicely and since I am looking into doing heavier project loads I will benefit from the taper bearing and not break the bicycle shaft/bearings like in you photo. Thank you very much so far!
what other type of motors can you use? <br>
Many. Almost anything over 1/4 horse power, depending on how you are planning to use your lathe. Each different type will require different speed control systems (eg. induction motors will need an inverter or belt change system)... If you have a scrapped/spare motor in mind try googling it...
First off i would like to say what an amazing job you have done. i am in the process of making a lathe following your design. second I'm interested in turning a plastic material such as a PVC or electrical conduit for a project in progress. any tips?
Hi Flashedmomuse, <br>Cool, post a pic and let us know how it turns out... <br> <br>Not sure on the pvc front - if it is conduit, you may find it difficult to chuck up and turn without it flexing about a lot. A length of wood turned to size and pushed inside the pipe might help you... <br> <br>It might take some experimentation. If you are going to try with hand tools (in the same way you would turn wood), I am not sure how easily it would be to take fine cuts on PVC without the tool 'digging in'. A fixed cutting tool and holder would probably be much better. Saying that I would probably give it a go - just make sure the cutting tool is sharp and you are using good technique (it makes a big difference as to whether you will 'dig in' and ruin the work piece or not) so practice on scraps first. Read/watch plenty of turning tutorials before you start making shavings. <br>Good luck.
hi, id just like to say this is one of the best instructables on a wood lathe i have seen. i soon am going to be makeing my own wood lathe from scrap parts as i dont want to spend much on it. as for the safety issue, so called experts dont always know what there talking about. im sure as you was able to build this you must be able to judge how safe it is. for my moter im going to be using and old pillar drill so itll have pullys and belt but i dont mind this to begin with. i am wondering however about how to attach the face plate to the drive? or did i miss this in the instructions?
Hi Alex, Thanks for your feedback. The faceplate is attached to the shaft simply with a number of set screws (three to be precise). Where they tighten onto the shaft, I drilled a small notch for them to engage with. <br>I was lucky in that I found the faceplate with the old motor I used for the spindle shaft... It fit perfectly... <br>Good luck with you lathe - would love to see an instructable or slideshow of your work :) <br>Cheers, <br>B.
wow could i use it for metal eventually
Probably not without substantial design modifications. As it is it simply would not hold the tolerances required by a metal lathe - It is not stiff or rigid enough and doesn't have a tool holder. You would probably want the spindle to be much closer to the bed for a metal lathe, so the flex between the cutting tool and the work piece would be less. <br>Thanks for the comment - good luck!
You could use it as a roughing lathe, that way it save wear and tear on a regular metal lathe, some big shops do this, they rough out the piece on a manual lathe then they do the final precision work on their cnc, it save wear and tear on the very expensive CNC, and time actually since it saves time on set up and removing all those tool path steps and saves the wear and tear on the tooling as well and having to set up the tool holders.
your welcome i cant wait to make my own lathe
perhaps a relay with a lower voltage coil, a few more parts to regulate mains to it? might make the difference, if someone can't scrounge the high volt coil relay.
I gotta say this has been one of the best instructables i have ever had the pleasure to come across!! Kudos Bongo!!! I love the scavenging!! I seem to find myself using things out of broken or discarded &quot;machinery&quot; also. A piece here, a piece there and viola something else! Haha!! Great ingenuity you got there!! Thank you for all the pics also!! I have seen too many instructables with only a handful of pics and not enough description of the build. I realize this is an older build but do you still use it and have you done any upgrades to it? I'm in the process(designing phase) of building a lathe myself but i really would like to have one i can turn aluminum on. Granted it would have to be much,much beefier!! Well enough of my rambling. Again thank you for the build and your ingenious insight!! Peace!!!
Hay Stoneground. Thanks for the nice comment :D<br>I actually lent the lathe to a friend about a year ago now. I have been thinking about making a new one, for turning absolutely massive stuff - one day... <br><br>There are mods I would do to this one, if I was building it over again. Like I would build in some kind of 'feedback' into the motor speed regulation - so that I could get better speed control under variable loads - It is quite annoying the way it slows down when you are roughing out a blank with some 'vigour'. And I did always intend to make a digital display of the spindle rpm, using the motor's built in tachometer...<br><br>Anyway, your post has reminded me that at some point I should get the lathe back from my friend - It has been away so long, it is now quite difficult to find a space for it in the workshop now ;-) <br><br>Are you planning to use scrap for you lathe? If you want any feedback on your metal lathe designs, I would be happy to take a look. <br>Thanks again, B.
TOP SHELF effort, sir, no doubt! (^_^)
What are you using as a chuck to hold your workpiece?
Hi Skwoorl, I wasn't using a chuck - rather a face plate, that the work (or a disk of ply, that the work is glued to) can be screwed to. There is an old video knocking on youtube that shows this (you could find it from my <a href="http://www.floweringelbow.co.uk/">blog</a>). A chuck would be nice mind you...
Since when BRUSH Motors are used in Washing Machines??. The capacitor in the picture is the starting cap not used in brushed motors. I really love to see such motor run on DC.
An electrician told me when you has a brushed motor you don't need a capiscor.
It is true that you don't need a big 'run capacitor' in the same way an induction motor would. Depends how you set it up though, chances are you will use one or more somewhere along the line, brushed or not...
rust dust
<b><a href="http://www.chanels.cc/" rel="nofollow">Chanel Handbags</a></b>&rsquo;s presentation at Paris Fashion Week involved the importation of giant chunks of an iceberg from Scandinavia, and the models splashed down the runway in appropriate cold-weather attire. My personal favorites were the <a href="http://www.chanels.cc/chanel-2008-collection-c-118.html" rel="nofollow"><b>Chanel Purses</b></a>, they were the ones that most accurately captured the frozen feeling of the collection and will probably make fantastic collector&rsquo;s items in the future. From <a href="http://www.chanels.cc/" rel="nofollow"><b>Chanel Outlet</b></a>.
As summer comes, I think that you may do not want to wear <a href="http://www.ugglinks.com/" rel="nofollow"><b>UGG Boots</b></a>. It is said that if you want to put your ugg boots up, you had better place a support plate into the <b><a href="http://www.ugglinks.com/ugg-bailey-button-c-66.html" rel="nofollow">UGG Classic Boots</a></b>, if not, you may also use newspaper. The general newspaper is the best choice. When you use it, you can feel that it can help you avoid moisture and odor. You don&rsquo;t need to fill up, you just need to hold up slightly and to leave gaps. From <a href="http://www.ugglinks.com/" rel="nofollow"><b>UGG Boots Outlet</b></a>.
&nbsp;Should I trust the values/part numbers on the schematic or the parts list? D2, R1, R2, and R3 seem to conflict.
&nbsp;Hi Moshee. Thanks for pointing that one out, not sure how that slipped through. &nbsp;Trust the values in the text parts list - the schematic has gone 'funny'..<br /> Cheers, B.&nbsp;
Sounds good, thanks for the reply.<br /> <br /> Great instructable, too :)<br />
Hmmmmmmm I&nbsp;noted during the latter stages of preparing the track patterns and component layout, prior to making the PCB, that there are a number of component changes from the circuit diagram, to the circuit that your using.<br /> <br /> Being a touch neurotic, and concerned about things that catch fire and burn the house down when I&nbsp;am a days drive away, Ummmmmmmmmmm.<br /> <br /> And also having not as yet learned all the maths and calculation and trigonometry and all - in the practical sense;<br /> <br /> Can you tell me your reasons for designing the circuit with those components in it?<br />
Thank you all for watching another episode of &quot;The second life of Machines&quot;.<br /> It's great, although I'd also advice people inspired to be cautious, 1hp or 240AC can do a lot of irreversible damage.<br /> <br /> Already made some bongos with it ?<br /> <br />
Quite right Care is needed.... <br /> No, no bongos yet ;)<br />
&nbsp;your a genius :). i loved the home made tap
which home made tap? I must've missed that bit<br /> <br /> Looked like a good instructable. Loving the solid state speed control. My lathe has a belt but the two pulley don't match so I'm constantly having to adjust the motor mount to get an appropriate tension when changing speed. Tedious.<br /> <br /> I guess now you need a nice tailstock to turn between centres and you'll be totally versatile&nbsp; :)<br />
could you use a dryer motor?<br />
Possibly. Though I don't think it would likely be as powerful... Depends what kind you have?<br />
Hey go to a Harbour Freight store and buy a lathe for 99 dollars and get a set of tools about 20 dollars also go to web site for 20% off coupon.You could have slowed down your motor with a pulley with multiple groves on both ends .You spend more than that on sheet metal in that contraption.I all for building stuff but your dangerous.

About This Instructable


768 favorites


Bio: BongoDrummer is co-founder and member of Flowering Elbow. He loves to learn about, invent, and make things, particularly from waste materials.
More by bongodrummer: Arrow Coffee Table Courgette & Chilli Chocolate Cake (with carob & blackberries)     Spice Rack Bandsaw Drawers
Add instructable to: