Clamp on timing belt pully or other mid-shaft encoding method?

[cadcoke5]

I need to put an encoder mid-shaft on some old equipment we are retrofitting. We can't put anything at the end of the shaft. The shaft is about 1 3/4" Dia.

Is there such a thing as a clamp-on timing belt pulley that we can put on without having to dismantle the machine?

I have very vague recollection about reading about a company making a shaft encoder that sensed the shaft position mid-shaft. But at the time I wasn't really involved, so am uncertain if I actually understood was it was.

A few more details if you are interested. A continuously rotating shaft, about 5 RPM. We need absolute position or angular measurement of 1 rotation, approx .1 deg precision.

Thank You,
Joe Dunfee

 

[drawoh]

cadcoke4,

What sort of stuff do you have on the shaft already?

You can get a gear tooth sensor, which ought to detect existing gears and sprockets, especially if they are steel. You would need some feature to provide an index pulse.

JHG

 

[cadcoke5]

I had wondered if something like the tooth sensor existed. But ended up not persuing it. In our case, the device is a very old loom. The teeth are dramatically oversized for the job. The pitch is around 1". I had doubts I could find something like this off the shelf.

Joe Dunfee

 

[IceStationZebra]

I use a mag pick-up to read flywheel teeth all the time. The problem with this is to get the resolution you want you would need 3600 teeth/rev. Or 360 teeth with a 1:10 step-up (could be a jackshaft with two gears).

I think in order to get absolute position in 0.1° precision you will need a hollow shaft encoder.

ISZ

 

[cadcoke5]

I guess it would be theoretically to install multiple tooth sensors, and space them so that they trigger in sequence, so to increase the resolution. However, I have doubts that the teeth are all in good enough shape that each tooth would trigger a sensor at the same location. I.e. a chipped tooth would be a problem.

But, I did find the term I needed to figure out for a clamp-on gear or sprocket. In the industry, it is known as a "split gear" or a "split sprocket". We will go with a split gear that we will clamp onto the shaft. A mating gear will be attached to the encoder.

I found a custom gear maker who has done this, but we may just purchase a pair of finished gears, and cut it ourselves. (the two are needed because, of course, we can't cut something in half and not loose material - the curf.)

Thanks for the input.

Joe Dunfee

 

[griffengm]

Don't know how far along you are on this but there is a garage door opener that uses a split gear assembly. Available at Menards.
FWIW. If it fits with minor modification, it might save you some time and $$$.

Griffy

 

[cadcoke5]

Of course, after persuing all of this, I talk with the guy in charge of the project, and he had another possible location of the encoder. It is not as desirable because it is further away from our equipment, but it is viable.

So, no split gear is going to be needed.

The next challenge is that this part of the shaft seems to have a redundant bearing and collar added, that we would like to take off to make more room for our stuff. But, the mystery is what is inside this undocumented gear box that is next to it... what is really inside? Are these apparently redundant parts REALLY redundant?

There are definitely some challenges to upgrading old equipment. But, it is also nice to work on old stuff. You see things you don't see on new equipment. Since we machine a lot of 1/2" plate in a CNC machine, we can make the items any shape we want. So I am inspired to make the brackets with some ornamental curves in them.

Joe Dunfee

 

[hydtools]

You have to love old engineering and art.

Ted