Tuesday, October 27, 2015

Bagging Scale

I put a homemade bagging scale onto my clean seed hopper to measure out 50 lb bags of seed.  I did not spend nearly as much time on this as I would have liked to, but so far it has bagged about 50 bags for me and it's working great. Here is a video I shot the first time I tried it:

The video depicts a spring-loaded bagg hanger which did not have enough strength to hold a 50 lb bag very well.  The next day I added a cam lock for the bag hanger, which is shown in the following pictures.  I glued some neoprene rubber onto the fingers to help grip the bags better.  I think inner tube rubber would also work.  It holds up those plastic burlap bags just fine, also. 100 lb bags would be fine as long as the balance beam was strong enough.  When I get a chance I need to work on the spring opening to make it easier to load a new bag.

Note the bag clamp  hangs from a single point.  I considered making the bag clamp integral to the balance beam but feel that hanging from a single point gives it a more accurate weigh.  Otherwise a swinging bag will throw off the weight setting.

The grain flows when the gate is pulled open.  A small rubber band pulls the gate shut.  The gate and guides are all sanded smooth and waxed.

I did not pay attention when drilling holes on the balance beam.  I would suggest measuring carefully from the fulcrum to the bag clamp hanging point, and then hanging the weights on the balance beam at obvious multiples, eg. 2 x or 4 x. Then adding or removing weights on the balance beam to change from, say, 25 lb to 50 lb bags will be easy.

NB: The fulcrum point is about 1/2" below a line drawn from where the weights are hung to where the bag clamp is hung.  This makes the beam "teeter totter" with authority when the bag is full.  A higher fulcrum point (I think) will make the beam tilt in gradual increments and (I think) make the bag weights less uniform.  You want the tipping point to have a waterfall effect, so that the trigger is pulled right when that last piece of grain goes into the bag.  This unit is filling up 50 lb bags with variance of about += 1 ounce.  I'm pretty happy with that!

Anyhow, the spring-loaded grain gate is held open by the bag-clamp apparatus (removed in the below picture for clarity), blocking this ramp-shaped piece of wood glued onto the grain gate.  When the bag fills up, the bag clamp drops down and no longer blocks this piece of wood, and the rubber bad pulls the gate shut.  In the below picture, part of the balance beam is doing essentially the same thing, holding the grain gate open.  In the upper right hand corner you can see a blue rubber band ready to pull the grain gate shut.

A view of the bag clamp on the bench.

To calibrate the scale, I just started hanging metal onto the long end of the balance beam until I got 50 lb bags.  Next time I will measure out and calculate, and maybe make a slick weight hanging system.  A farm scale might be useful as a starting point, but note that a farm scale does not have the crisp "waterfall" effect that we want to trip the grain gate.  The fulcrum point might need to be changed.

To do:  getting a 50 lb bag out of the clamp is a little awkward, and sometimes I get a small tear in the bag from the bag dropping to the floor when the clamp is opened up.  It might be possible to have the balance beam set the bag on the ground gently, somehow.

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