Hoist and releasing tong build

I see that the photos upload in very low resolution—-sorry they can’t be clearly read The bars for the tongs are 1/4” thick. They have plenty of rigidity for the A20 full of iron that I routinely lift. Heat exposure in the furnace is brief enough that they never get hot enough to weaken.

Denis

 

I'm going to weld up a copy of these tongs soon. I was wondering if you had any close up pics of the way you put the pouring cart together? I have an idea but it would be nice to see what you did as a reference.

I got regular bearings that I will weld onto the outer casing.

 

Happy to provide photos as needed. Just let me know. I am traveling right now. So, there might be a slow “response time” on my end. Both the trolley and hoist have proven themselves.

One small trolley modification I am considering is to split the ring that holds the crucible. My new habit is to let the crucible cool outside the furnace while held by the trolley. If the ring is not cut, I worry it could put too much constrictive force on the crucible. So, for now I make sure the crucible is sitting on a support and not actually suspended in the ring as the crucible cools(after it initially transferred heat to the ring and thus temporarily increased the ring circumference). Might be needless worry, but I did notice the crucible to be pretty tightly held/wedged in the ring the one time I just left it suspended to cool.

Denis

 

My tongs are nearly done but when I was testing them I found that they open just fine with the cable but when lowered around the crucible they do not grab the crucible with enough force to hold it. The tongs just slip open like one of those weak stuffed toy claws. How did you manage to make yours grip?

 

add more quarters and try you luck again.

 

After talking to Zapins and reviewing the photos I posted earlier in this thread I can see that it is not clear how the trapezoidal cage with rivets is constructed. If one looks at post 17 dated April 12 2018, you will see a photo that has a picture of the trapezoid and rivets are pointed out and has the words "Top of Tong." What is not clear from the photos or description is that there is a single piece of flat bar traversing the top of the trapezoid ending just shy of the tong bars and held in place by the two rivets each located just lateral to the attachment of the turnbuckles. That piece prevents the tong arms from being able to pivot toward the center and causes them to establish a grip on the crucible. I will try to make a photo of that portion of the mechanism in the next couple of days---as soon as I travel out to the barn 15 min from here. Arrrggh. I tried to include every detail of the construction in my photos, but missed that key point. My apologies.

Denis

 

I thought your description was fine. The bars are each supported by two points, the bottom of the frame on the outside and the rivets (I thought they were rollers) on the top inside. I figured Zap wasn't finished, which he isn't.

 

Promised a month ago I finally remembered when I was at the foundry to take a top-view photo of the assembly that holds the lifting tong bars. I wanted to illustrate the piece of 1/4 x3/4” x roughly 5” piece that is riveted in place that prevents the tong bats from collapsing center wards as the assembly is lifted.

 

I have added a stop to my crucible lifting tong device. As I work alone, I was concerned that I might find myself in a situation in which after lifting the crucible out of the furnace, I did not want to put it in the trolley ring and did also not want to put it back into the furnace. This might occur if part of the “ saucer” I use on top of the plinth was stuck to the bottom of the crucible, but not the entire saucer was stuck on. That would cause the Crucible to topple over if I tried to set it down. If I had to keep the crucible suspended in the air so that I could knock off part of the remaining saucer, I’d have a difficult time holding onto the lift with one hand and trying to push the piece off with the other as the crucible is 7 feet from where I stand. Locking the lift more or less horizontal would be the answer. Then I could walk to the crucible, do what was needed and then release the lift and proceed.

The lock is essentially a rectangular steel block pinned to a 3/8” steel rod with a comfortable knob pinned to the outboard end. The assembly is suspended from the bottom of the hoist boom by a couple drilled tabs welded to the boom.

Here is the lock in action and some stills of it as well. Most likely the photos are self-explanatory.


Here's a closeup of the block movement:


The push /pull knob


the knob, rod, block assembly


Detail




Crucible suspended with lock engaged


I'll add that I have been using this hoist for 2.5 years without a hiccup. It has been very reliable and easy to use.

Denis

 

Very smart idea. I need to return to this and finish it up. It was one of the dozen or so projects I put on pause due to life. I still need to sort out the swivel bearing in the top part of the arm then fix the tongs so they lock onto the crucible properly.

 

I think you will be pleased with the setup. It is safe and robust. If I can be of any help, let me know. This one works for both an A20 and A25 Super Salamander.

Denis

 

Wonderful work and thank you for sharing it with us Denis.

Is it possible to show a motion close-up of how the wedge is lifted? I still haven't got the concept into my thick head yet,

Cheers Charlie

 

I tried a pipe in pipe but there seems to be too much friction. I think it needs a bearing. I'd rather avoid machining a tube with 2 bearings inside, I'd much rather just buy one, but I guess there aren't premade easy to find ones I can find.

 

I’ll see if I can do more video the next time I am out at the foundry and have hoist set up. The “wedge” is not wedge shaped but is just a rectangular block of steel with a 3/8” bar attached. The bar slides suspended by two tabs from the bottom of the boom. Moved forward it jambs into the space between the boom and the support on which the boom pivots up and down. Moved back, it no longer interferes with tilt of the boom.

Denis

 

I can’t think of a pre-made thrust bearing joint. Though the lower end of the offset vertical arm uses a thrust bearing, machining it was not close-tolerance work by any means.
Here is the roller portion and here are what should be two washers

All you need to do is make a non-precision spindle with a shoulder. The support tube bears on the lower washer and the offset arm bears on the upper washer. I’ll take pics. What I made is relatively crude but works fine. It gets dirt in it and might get wet in the rain—-no problem. It’s like the old VW Beetle—- low tech, easily serviceable, but reliable.

Denis

 

Another option for a bearing unit would be a trailer stub axle and hub assembly: cheap, pre made, reasonably weatherproof and ready to weld on.

 

Cheap as chips.

https://www.amazon.com/Southwest-Wh...ocphy=9031529&hvtargid=pla-633829956877&psc=1

 

Well, I did get out to the barn/foundry this morning to repair a window up in the peak that needed to be put back on its hinges and needed reputtying. I was able to photograph the bearings and spindle stub. I forgot there is a caged bearing on the spindle too.
https://www.amazon.com/gp/product/B002IG1B84/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

And here are a couple pics of the spindle—-I told you it was dirty The spindle just fits into a socket to hold the bearing with a non-precision fit.


​

 

I actually think using a wheel bearing like Mark posted may be a simpler. though slightly bulkier (should not really matter), solution. It certainly would be hell for strong and would pivot easily. If desired, much of the bolt flange could be machined off and just weld pipes to it rather than bolts and flange to mate.

Denis

 

How about a bicycle head stock?