MARBLE LIFTING AUTOMATION

[Arbalest]

Brian's project continues here:

http://www.homemodelenginemachinist.com/f31/marble-lifting-automation-21920/

[Admiral_dk]

What a shame that it's gone from here ....

Yes I know it isn't an engine, but Brian normally shows how to in a nice way.

[Brian Rupnow]

It seems that the rules have changed a bit, and I can now continue my Magnificent Marble Machine.
A rooty tooty toot and a riggy jiggy jig and the parts start piling up!! Now I have to figure out a way to hold a hacksaw blade in my axa tool holder to cut some e-clip grooves on the lathe---

[Brian Rupnow]

Not one of my better digital photographs, but--That whole e-clip and welded link thing went very well. I had put a .030 x 45 degree bevel on the side of the link arms that was to receive the "weld"--actually silver solder, and a .040 x 45 degree chamfer on the head of the 1/4" round cold rolled. That way when everything is ground flush, I still have lots of silver solder in the joint.

[Brian Rupnow]

Oh Yeah!!! I like this!!--Its starting to look like one of those old time killer catapults they used to knock down castle walls----

[Brian Rupnow]

Ready---Aim----Holy Crow--I'd hate to be on the receiving end of that ball bearing!! Actually, the arm is just about at the elevation where the ball bearing topples out from gravity. Its plain that if I want the ball to stay in the pocket until the arm is vertical, I'm going to have to put a neodymium magnet in the bottom of the pocket.

[Brian Rupnow]

Keep your heads down boys!! As soon as I get some dry powder for this thing--KABLOOOY!!! I got up early this morning and made the base before Momma got up. Now she's up, and I have to go get involved in the "Big house Slick up"--Kids and Grandkids and spouses and friends are coming for Thanksgiving tomorrow and Mommas back isn't real good, so I get the vacuuming duties.

[Brian Rupnow]

After my vacuuming duties, and my lawn cutting duties, I stole a couple more hours and machined the hold downs for the slider base. No excitement there, just milling and adding counter-bored holes. With all of the bolts tightened down, the slider still slides, so I must have got the clearances about where I wanted them to be. One thing I'm beginning to see is that I may need to put a gear drive on this thing rather than a simple o-ring drive. O-rings make great drive belts for this model engineering stuff, but they really won't transmit very much torque. They just slip. I think I'm going to change the pulley shown in the model for a spur gear about 4 1/2" in diameter and drive it with a 3/4" diameter pinion on a jackshaft. I will put the o-ring pulley on the jack shaft. I went around to all the motorcycle and ATV repair shops yesterday, trying to mooch any old spur gears, but no luck. I can cut my own spur gear, but I would rather have found a "ready made" set. I did get an electric motor armature with a 1/2" diameter helical end on it and a matching 1.5" diameter helical gear, but there isn't enough reduction in that, so I'll save it for a future project.

[Brian Rupnow]

For what its worth--I sat pondering this mechanism today, and thinking that something wasn't quite right. I know it will work mechanically, that wasn't it. I went back to Youtube and watched a dozen similar marble lifting mechanisms. Then suddenly it hit me!!--Although my mechanism might work flawlessly, there was absolutely nothing to prevent the marble from falling out either side of the two pieces of angle that it sets between. I kicked this dog around for a while, not wanting to have to get into a major redesign. The solution I came up with was to reduce the center section of crankshaft from 1/2" diameter to 3/8" diameter, and put a couple of 1/16" "shields" on, one on each side of the angles, with 7/16" slots in them to let the crank slide in. The "marble" shown in red, can't get out through the 7/16" slot in the side shields (transparent yellow). I may have to slot the bottom of the shield to get it around the crankshaft, or I may just leave the bottom of the slope open--the marble never gets down to the bottom anyways.

[Brian Rupnow]

Yes, I know. Its looking stranger and stranger---but so far its all good, haven't made anything backwards yet. I have the two angles that trap the bronze slider that makes everything go round and round, and the back bearing support, which also holds the overhead dark blue piece with the holes for the marbles in it.

[Brian Rupnow]

And that girls and boys, is the front bearing support. I didn't have a piece of 1/2" cold rolled shaft to stick in the bearing supports, so I stuck one of my "sharpie" pens in the bearings. When the real crankshaft (maybe I should call it an offset shaft) gets in there, it will have a 3/4" offset "throw" riding in a brass slider block between those angles. That's what will make things go back and forth.

[Brian Rupnow]

This is going to require a fair bit of torque to drive it---thus the reduction gears shown.

[Brian Rupnow]

Tonight I machined the brass slider block that fits on the "throw" of the crankshaft and rides between the two angles to make them slide back and forth as the crankshaft revolves. I used the old connecting rod trick, where-as I split the block of brass, bolted the two pieces back together, and then drilled and reamed on the split line. That lets me assemble it around the crankshaft. In the first picture the brass is upside down, so you can see the six #4-40 bolts which are countersunk in the one half and drilled and tapped in the other half. The second picture shows the piece of brass flipped over, so you can see the plain top that contacts the "marbles".

[Brian Rupnow]

 Tonights bite of the elephant was that vertical piece of 1" x 1/4" with the two holes at the top. The next step will be the 1" square horizontal piece with the holes in it for the marbles to enter and exit. (It shows up as transparent blue in the 3D model.) I really don't know what to expect with it, because in spite of the wonders of 3D cad, there are some things you just can't tell about until you make it and see. I hope it goes as well as all the rest of it has so far. I'm not going to invest any times making gears until I'm sure it is going to work.--Speaking of gears, in the background you can see the armature with the helical gear cut into the 1/2" diameter end and the 1.5" diameter helical gear it mates with. I scrounged the pair out of a scrap bin at the local "fix-it" shop. I haven't has time to see if the material is too hard to bore for a center hole or not.

[Brian Rupnow]

We have good news to report on the marble moving front. The side shields do work to keep the marbles from falling out thru the sides, and with just the right combination of magnets glued into the back side of the pitching arm, the marble doesn't drop out before its supposed to. Nothing seems to jam or bind, and the speed you see things running at in this video is far more representative of the speed the machine will run at when powered by one of my i.c engines.