Hi, I just got hold of a nice Sankyo 431E. Pity though it is running too fast. I timed a number of times and it quite consistently does a minute in 55 seconds. Now I'm totally puzzled. The motor is for the correct frequency (50Hz) and as far as I can see it should sync to that. If it would run slower I could think of possible causes like friction or worn gears, but too fast?? Before I take it further apart I thought I better ask for advice here. Anybody any idea?
-
-
I am not sure why it would run fast when it has the correct motor for your electrical grid/frequency.
I know the motors are rebuildable and I have restored a few that had cracked gears: https://www.ebay.com/itm/Arrow-Ball-...sAAOSwJhRfOxtF
These gears are still too small for current 3D printing resolution, it seems.
I don't know if the rebuild gear kits are for 50hz models. I know, in Copal motors, they merely change the gear ratio to compensate for frequency changes. -
This looks like it could be compatible, albeit it expensive, even without the shipping cost. You might be able to find this closer to home? No guarantees that it will fit though.
You are in luck with this type of motor in the Sankyo. You have 2 options, one motor is non-serviceable and this one you can at least open up and see what could be wrong. On the outside of the Sankyo clock you cannot see which type of motor is inside so I usually steer clear from these unless they are very cheap, I would take the risk.Comment
-
I opened it up and it has indeed a cracked gear (see first picture).
And now I also understand why it is running too fast! If you look at my second picture you see the crack as become so wide that it skips a teeth. So this 12 teeth gear effectively becomes a 13 teeth. And 12/13 * 60 = 55.38 seconds! Pretty close to what I measured. Never could have imagined that :-)
Today I also got delivered a Sankyo 101 with a broken motor (I new it was broken when I bought it). Also a broken gear, so now I need two replacement gear sets/motors. I will look what options I can find.
Thanks for your help and the pointers!Comment
-
Yes, that's quite common with these Intermatic motors, but I usually see the larger gear getting cracked. The plastic get VERY brittle over time. Underneath the damaged drive gear you may find old grease that has dried out, as well.Comment
-
Finally fixed it!
After a long search found a more or less matching gear on Ali Express (some part of a model quadcopter):
https://nl.aliexpress.com/item/4000031705422.html?spm=a2g0s.12269583.0.0.58961de9 dkoy41
It has 12 teeth, outer diameter 4.2 mm and inner 1.2 mm.
The outer diameter is a little less than it should be, but the closest I could find.
The height is just right.
I first scraped away the remains of the old gear. That is easy.
Then the hard bit: the gear has an inner diameter of 1.2 mm while it needs to be mounted need on the metal bushing of 2.5 mm diameter.
So I needed to drill a 2.5 mm hole in it. I tried several way of keeping hold of the gear while drilling, but in the end felt the safest one was to just hold it in my fingers while using a power drill at a low speed. The advantage of this is that you feel what is going on, correct the direction and can stop/let go if the drill takes a too deep bite in the plastic (the gear is tiny so the drill is comparatively huge). When that was done it was still a bit too tight, so I used a file and the drill again to make widen it until it fitted tightly on the bushing. As you can see in the pictures there is not much room for error as there is little left of the gear.
Both motors are running fine again :-)Comment
-
I found one of these motors (inside a clock) in my pile of spart parts and decided to have a go with this new gear since it is clearly this particular gear that is broken. The link posted by Johan does not seem to work. I will attach an alternative link, which worked for me.Comment
-
I have three of these clocks all with the same problem. Surprisingly, although the larger gear is more fragile, it was always the smaller gear that was either split or mashed. I have had success with one of the clocks using Johan's method but drilling out those small gears accurately so they sit properly is a real challenge.Comment
-
Thanks for that, I ordered 2x 10 gears, so should be able to get one in at least
When the larger gear goes, that will be an issue I guess for it is a bit more complicated gear, but that's for next time...Comment
-
Here is an alternative to the plastic gears on Ali Express. They are copper with a 1.98 mm centre hole. They are 4 mm high but that should not be a problem and perhaps being metal, they won't distort when drilling them out. Worth a try?
Comment
-
Correction. They are described as copper but the appear to be brass.Comment
-
I decided to bite the bullet and buy a couple of Intermatic gear sets as only one attempt at drilling out a replacement plastic gear has been successful. The gears arrived today. While the smaller gear fits correctly, the hole on the larger gear is too small to fit the shaft in the motor. I carefully drilled it out and it fits now. This has been the case on both of the Sankyo Model 101 clocks I have. The motor number is WG6A6A 4X07. These are 240 volt, 50 cycle clocks. At least the new plastic gears are not as fragile as the old ones.
Comment
-
Today I bought another 431, this time running too slow, about 5 seconds per minute.
When I bought it I could not yet think up what what caused it, but once I opened the motor it became immediately clear. It had the same root cause (a broken gear), but a different failure mode. The pinion had lost two adjacent teeth, which allowed it to skip a step. This made it effectively an 11 teeth gear instead of 12. Doing the math: 12/11 * 60 = 65.5 seconds. Exactly what the previous owner mentioned and I measured myself
The skipping of the teeth also explained the ticking sound it produced while running.
To fix it I used one of the Ali Express gears again. This time though I first increased the width of the gear by the 'hit it with a hammer' method as described in this post. The original gear is 4.6 mm. The Ali Express gear was 4.2 mm which I grew to about 4.4 mm by the hammer treatment (I did not dare to go much further to not deform it too much). This made a better fit, but I then spoiled it a bit by going a bit off center while drilling. Drilling the hole is the difficult step. I think the best approach is to drill a slightly smaller hole and then use a file to correct any error. Patience (lots of it!) is key in this step. Well, I first see how long this one lasts. New gears are still available from Ali and dead cheap.
And here is the end result: a lovely 431C in rare blue color. Apart from the broken gear it is in mint condition (the white paint on the screws showed it was not opened before). Very happy to make it work again!
Comment
-
Update:
the above fix kept the clock running, but rather noisy. I suspect that this was due to the off center drilling of the gear, so I had another try and also changed technique in two areas:- Instead of using the rather crude hammer method to increase the diameter of the gear I had another crazy idea and used a hand riveter to compress the gear. This gave much better control and spread the gear evenly. The convex shape of the rivet helps to spread the gear at the top, that is also the part where it meets the other gear.
- Instead of drilling 2.5 mm at once I used several drills of increasing diameter like Daddy-O did, and then finish it off with a file to reach the required diameter.
Comment
-
Good work Johan and thanks for sharing this! I can confirm that the drilling in stages really helps to keep the main hole focused on the middle of the gear without needing access to specialized tools, I drilled by hand, manually, that also helped to speed things down.Comment
Comment