Gearless Clock – Pulley Setup
I got the weight pulley system together which took a lot longer than I expected! These little things were tricky to make!
They each run on a tiny bearing;
Because they are only about 3mm wide, I found it really tricky to have a blind hole to a press fit. It was too tight and I ended up killing the little bearing trying to press it into the housing, or it slipped into place. Consequently I had to loctite the bearing into the housing:
Then I made some small shaft for them to sit on:
I managed to get it all hooked up. I then needed a way of checking the weight required in the both the master and jockey weight before cutting any 2″ dia steel to size! Both Woodward and Wilding explain that the jockey weight and master weight are dependent on the line used and pulley setup. Woodward used nylon fishing line but this seems to offer no resistence. A kind chap from the NAWCC forum sent me a length of nylon line but like Wilding and Gadget builder, I couldn`t get enough friction and the line just slipped. I am currently using builders braded line and it is working well. I`ve used a coffee jar full off steel offcuts as the master weight which allows me to adjust the weight. I`ve still not got this quite right. I think my jockey weight it too heavy at present. I had the clock running for about 45mins but the pendulum slowly slowly slowly dropped, indicating the master weight on the centre wheel isn`t heavy enough. Woodward did use a much heavier weight than Wilding, and I`m currently using the smaller weight recommended by Wilding. Tomorrow I`ll adjust this, but the clock is running with the pulley…I just need to get the weight and jockey weight sorted and then I can move to the dreaded daisy motion!!!
In a desperate attempt to get the clock running, I`d used a hoop on the coffee jar lid which wasn`t allowing the line to slip correctly and if you look at my picture above, it was pulling the line down off the pin wheel at an angle. I made a very rough pulley based on Wildings plans. I will need to shape and finish this to make it look more elegant, but it will transfer to the master weight when I`m happy with everything.
Once this was on the clock, I found most of my problems went away but I still struggled with pendulum losing momentum. Woodward suggested 1400g master weight with the jockey weight being 60% of this when used with nylon monofilament line to stop slippage. Wilding used only a 700g master weight and although he explained Woodwards ideas, he admittedly used a far smaller jockey weight than the 60% suggestion. I was using about 850-900g in my master weight (because I was trying to get the pendulum to have a bigger impulse) and about 200g in my jockey weight. Wilding did mention you could use less “if you could get away with it” and because the braided builders line has much more “grip” than any monofilament fishing line, I experiments to see what the minimum I could use was. Using too little jockey mass and the line would slip and the master weight would slowly fall, however using a small M10 bolt and adding nuts as extras weights, I got to about 50g for the jockey weight.
This made all the difference and my problems with impulse had gone! The clock was running… but that lead to another problem…!!!
With the bigger impulse, the backstop pawl started jumping again! This is something John (gadget builder) and I have been discussing for a while but no amount of bending of the wire could stop it. The position Wilding suggestions will clearly work but even if you don`t get the jumping I was experiencing, this low position of the backstop is not ideal. Really the backstop should be acting in a more horizontal position like the count pawl is acting in on the pendulum rod. This will allow it to easily lift and drop off each tooth, especially the deeper one I was having problems with. John suggested a better position for the bridge would actually be at a 30 deg angle! This wouldn`t look great in my opinion, but the higher position of the backstop would at least reduce the force on the count wheel. This was irrelevant anyway as it was installed on the clock!
The other option would be to take a bracket off the right bridge pillar and mount the backstop on there! So that it was free to move I used a small bearings. To reduce friction even more, I intentionally increased the length of the backstop wire and hooked the back end so that I could add small washers as weights to counter-balance the backstop. This made a MASSIVE difference, both the position and the counter balance. The position stopped it from jumping all together and by adding the small weights, you could tell friction was reduced because the back stop became silent in action! :ddb:
Now, I made this as a quick job and haven`t shaped it or polished it and clearly I`m not going to use washers to counterbalance the system on the final thing!!! I just stuck it on to see if it would work, but once I`ve made this look OK it will be installed. The bracket needs rounding at both ends and making much narrower:
It has been running since 10am this morning which is about 10 hours 30 mins of running time. Fingers crossed it is still going tomorrow morning!!
This will later be modified to a doubled pulley line to get less drop of the weight per day…