Homemade Engine Clutch

I found a problem with my engine; it wont start under any significant load. The second pulley I made meant it was extremely difficult to start.

pulley = no startMain pulley off engine

I needed a clutch at some point anyway so I started thinking about how I could resolve both problems at once, removing as much load off the engine on startup and being able to clutch the engine.
My plan is to put a small disk on the bottom of the shaft, then create a method of being able to push the pulley onto it; a dry friction clutch, but with a few changes. The clutch control will be a nut that I turn remotely (Likely by another pulley). The reason for this is it means I will be able to apply more force to the connecting plates via the bolt, and possibly later I may be able to automate it (ie, mechanical clutch)
Also it seems like it will be the easiest to build.

This is what I imagine it would assemble like (click for big)


first home made clutch assembly prototype design

More detail on the bottom of the pulley:
Clutch design prototype other views

The pulley will turn freely inside the bolt, I may later replace the bolt and bearings with a real bearing perhaps out of a skateboard or something. The bolt pushes the pulley up using the two lower fixed nuts, turning the bolt inside them will push itself up up.

Update 16 July 2010
I started working on the pulley/clutch shaft and bearing. I spent most of the time trying to hammer, screw, grind some washers to the right shape. the most successfull was one that I ground down with an angle grinder except for the middle, then bashed the sides up a little bit. I found a aluminium ring which I think came from a hard drive and installed that and it seems to hold everything quite nice. Its not anywhere near perfect, not even near good, but its usable for now.


Exploded pulley with shaft and bearingsassembled pulley with bearings and various bolts
(Click for big)

The left picture shows an exploded simulation of how the bearing fits together, surprisingly this doesnt work too bad. The right image shows what it could look like assembled. Note the bit that says ‘Clutch Control’ this is just a bolt and two washers for image purposes. I need to put some thought into how I will turn the shaft, without allowing the spinning pulley to have any control over it. if I used a smaller pulley down the bottom or in the middle (as pictured), I fear it would be too easy for it to slip and the engine would dis-engage the clutch automatically. I also found I will need to modify the holes that the top bolt and bearing fit into; they are too shallow.

Update 17 July 2010
Started building the new base, and resunk the pulley so I had more bolt to play with, I am pretty happy with it. then I sunk a bolt into a wooden beam to go under the engine shaft, I shaped it with a craft knife, chiseled it out a little bit, then wacked it in with a hammer. It feels really solid so I am happy with this part. I in the 3rd pic I have placed it roughly where I expect it to sit. But I noticed I will have to be quite precise, I dont want the too shafts to be mis-aligned because it will mean the clutch plates wont sit true.


new base in progress

bolt mounted in a small beam to hold the clutchPlaced clutch in base underside of placed clutch

I still havent figured out how I can turn the clutch shaft without using too much bolt real estate and keeping it secure so its not able to be spun by the engine. although I am thinking about two small pulleys with some rope attached and wraped around a few times. buy pulling one rope, the pulley will spin the shaft and the height will increase, at the same time another pulley will be pulled and wrapped around the second pulley. I can then pull the second rope to do the opposite.

    Wooden Pulleys – Turning

As per Part 1. I now have a working drill and hole saw that runs of an old computer power supply. I can turn wood with the same drill by mounting it in a vice and bolting the wood into the chuck.
Power supplyDrill running off ATX PSU Drill Lathe

Firstly I took an old piece of MDF that was once a set of shelves, then a speaker box, and now wasting away in the garage and cut two pieces out. One was 5″ the other 4″. It took about 10/15mins to get through the MDF, I thought the drill bits were a bit crap but I think the drill itself is probably still underpowered. (it was quite a cheap unit when I bought it) Also I found it was very easy to get on an angle, possibly the density of the wood was different nearer the edges but I found it was digging in quite a fair amount on one side or the other and I ended up with not very even pieces. The first one wasn’t so bad but the second significantly skew. I will borrow a drill press to try and get a better piece, at least until I build my own later.

I put a bolt down the center shaft and tightened it up and placed the bolt into the chuck of my drill, then mounted the drill in the vice. To get foot control I tied a rope around the trigger, which travelled along my workbench to a nail then down and tied to a metal ruler/level at a height where I could push it down to pull the rope and as such, pull the trigger. I had some control over speed, but it could definately be improved.

Working on first pulleyPulley being turned and carved

This is how it came out, I was quite happy with this result.
Finished MDF pulley

I built a second but it came out quite skew, I will use a drill press to re-cut the MDF, and if its faster than the hand drill I might cut two circles, and stick them together to form a bigger pulley. something like so:

plan for new wood pulleycross section new wood pulley
This will also give me a wider groove so I can use thicker belts.

Update 12 July 2010
I also refined my drill/lathe technique a little over the weekend. I think I will modify it further to become a slightly more permanent fixture with a bearing on the other side. because its only fixed to the drill its quite easy to push too hard and bend the drill which alters the shape of the turned wood. to start with I may just buy a 30cm peice of threaded steel, grind myself a nice 3 sided head on one side so that it fits into the drill nicely, and smooth the otherside and it can sit in some sort of fixed socket to provide a more stable shaft.

I also built the new pulley, twice as wide so it will accomodate more reasonably sized belts.


Pulley 3Pulley 3

Currently my plan for the belt is to use rubber from an old push-bike inner tube

    Wooden Pulleys – Equipment

(5 July 2010) – Power and Drills

First thing I needed for my generator was either cogs or a pulley/belt system to drive the washing machine engine. I thought about several different options from buying old car pulleys/belt, using a bevel/helical gear, or building my own cogs/gears/pulleys on the cheap.

I decided the cheapest option (since all my projects try to be as low cost as possible) for me is to try manufacture my own pulley’s from wood.
I needed a few things,

* Hole saw
* Reliable drill to run the saw
* Wood turning equipment to cut the grooves.

I had none of these so started with what I did have.

I had an old portable battery drill that had a battery that was dead and generally ready for the trash, I figured I could wire it into the mains and turns out I was able to find an old ATX PSU that put out enough power, so I snipped all the ATX connectors down fit inside case, covered the ends up with heatshrink (didn’t want one accidentally touching something) and rigged up a switch and so on so I could run it like a lab power supply.


Modified ATX Power SupplyModified ATX Power Supply

(This PSU came in quite handy for other 12v (ish) projects like a peltier effect device I am playing around with.)

So now I have power, then I removed the casing of my drill battery pack, removed all the battery’s and chucked them (they were quite corroded) then basically clamped two cables to the connectors that go inside the drill, unfortunately it wouldn’t let me solder them on so I ended up turning the metal sheet over to clamp the cable in. I tied a knot in the cables before the hole so they wouldn’t tug on the connection. Then ran about 2.5m of cable out to a Molex Plug I picked up from jaycar so I could plug it neatly into the PSU.


Drill with modified battery pack to run off 12v powerportable drill running off power supply

I ended up buying a hole saw, I didnt have anything I could modify to make that, but it was only $20.

For the Lathe/Wood turner I found I could bolt the wood I wanted into work with into the drill, and mount the drill into a small vice and I used a rope tied around the trigger, around a nail, down to a metal level so I had it foot controlled. but I talk about this more in part 2.

Wood turning and Pulley making with a drill in a vice


(17 July 2010) – New Wood Turner

Ive started working on a new wood turner (I cant really call it a lathe as its shaft reliant) pics now, further update coming later.


taking the drill apart
drill too far apartmaking the mount for the drill motor

wood turner mount in progresswood turner mount in progress, side angle

(click for big)

the offcuts from the MDF I was using to make the pulley’s is used (leave no wood scraps behind) so its all odd shapes, its almost artistic! I just need to cut the bottom to a standard height, mount it to a small board, then figure out what ill mount that to. Probably make it like a vice that can be moved around, bench mountable, I also need to make another end that holds the other side of the shaft so that the shaft is stable, not able to move around, which is the biggest problem with the drill-in-a-vice “lathe”.


(28 July 2010) – New Wood Turner: Wiring

I finished wiring and testing the new setup. Power comes off the other psuedo drill pack and I’ve just hacked the bottom off the drill I am using for the turning. Power then goes too the jandal controller for analogue (ie: more presssure more speed) control of the motor. I mounted the original drill control into a recess into the bottom jandal and glued the jandals together. then it goes off to the drill in the mount.

new lathe wired up
Lathe jandal pedal
lathe power 'wiring'