Chris's Marion 91 Steam Shovel

[crueby]

Continuing on with the drive shafts, turned the drive dogs (drive dog, thats what I should be calling these ones on the shaft, not clutch dogs!)  to shape, then cut the teeth in them just like before.

Then took some 2-56 screws, held in a 3/32 collet in the square holder in the mill vise, and milled the heads square to mimic the originals.


An assembly so far:

and where it sits on the model:

Last steps on these shafts will be to make the keys to hold the parts, then some paint...

[crueby]

This evening I got the keyways cut - one short one in the center for the drive dog, another longer one at the outboard end for that shell.

Then time to do some filing in the shaft holes of those parts to match the key, so far I have both parts on one shaft fitted, will start the other pair tomorrow.

[10KPete]

I think I have it figured out; those tracks are a fair distance apart and to minimize the turning radius of the shovel, twer it mine, I would want to disconnect one side of the axle to avoid over/under driving one of the tracks. Sorta like a tight turn ( not pivot ) on a Cat.....?????

Those parts look huge until you stick your big paws in the picture..

Pete

[Don1966]

No that’s cool Dog looking like you got a handle on it. 


 
Don

[crueby]

I think I have it figured out; those tracks are a fair distance apart and to minimize the turning radius of the shovel, twer it mine, I would want to disconnect one side of the axle to avoid over/under driving one of the tracks. Sorta like a tight turn ( not pivot ) on a Cat.....?????

Those parts look huge until you stick your big paws in the picture..

Pete

Hi Pete,
I doubt it - if you run the drive dog down, the end shell moves down too, and then the shaft end falls down on the ground.  Probably several hundred pounds at least of parts to move back into place... Seems like if they wanted to do that, there would have to be another stop collar under the big shell, to let it freewheel but not slide down if the dog was moved, like the center gear clutch does.

The rear tracks can pivot about 20 degrees to the side at most, which would give a fairly tight turn for such a huge and heavy machine. My own belief is that the dog is there to let the parts be assembled in the first place, and then were left that way. Given how well engineered everything else is, if they wanted to disengage one side, they would have put in a control for it, or at least a more robust lever or handwheel on the set screw. But, that opinion is not backed up by any documentation or anything from the time, just my assembling the thing on the bench, and moving that dog down is the only way to do it. The patent papers don't mention anything about driving one side only, and in fact give the option of driving both rear tracks as well as the front from yet another steam engine mounted on the rear axle block.

Seems like if you only drove one track, it probably would not have enough traction to move against any incline or rough surface - the track plates themselves are dead flat and smooth, no ridges on them at all. They were only doing half a mile an hour at top speed, and I doubt they cared about tearing up the ground with a little sliding in a turn like a road vehicle would have to deal with. If they did, they could have added a differential, which existed long before this track system was made in the 1920's. They had over 110 tons of machine to move a few yards to the next bit of digging, I think they needed both driving to move it in most cases.

Sigh. One of these days I'll get a look at a early 20's catalog and see what it says - I think the HCEA has some from that period, but with just one very overworked volunteer researcher there, getting things like this looked up and replied to takes forever and many contacts.

Oh, and for scale, that drive shaft is 3/8" diameter, the paws are way out of scale!

[10KPete]

Yep, I think you're right, Chris. I forgot you'd said the 'rear' tracks would pivot 20*. The 'quick' engagement had to be for assembly purposes...

Pete

[crueby]

Yep, I think you're right, Chris. I forgot you'd said the 'rear' tracks would pivot 20*. The 'quick' engagement had to be for assembly purposes...

Pete

And, after all that explanation, guessing, and figuring, someday I'll find some more documentation and find out I am all wet!

[gunna]

Those parts look huge until you stick your big paws in the picture..
Pete

I have to agree with Pete. Sometimes it is hard to envision just what size machine we are looking at. Those shots in your hand bring it all back to scale. Still watching in awe.
Ian.

[kvom]

What would be interesting to know is how it was used.  Obviously if it just moved forward it would cut a "slot" with a width determined by the boom's swing.

[crueby]

What would be interesting to know is how it was used.  Obviously if it just moved forward it would cut a "slot" with a width determined by the boom's swing.

In the catalolgs they have a large section of photos of the shovels in use by customers, and the usage varied all over. There were ones used by the railroads to maintain ditches, they would roll down the tracks taking out the ditch on either side as the advanced in short steps. Others were used to dig canals, digging in front and dumping off to the sides. In quarries, a lot of times they would advance along an embankment taking off a section at a time, or they would clear an area to one level, then ramp down inside that and take the pit deeper, leaving a spiral ramp. Large building foundations could be taken out that way too. Some showed them on wide 'legs' supporting them across a ditch for subways or sewers. There were even special ones with short booms and driven by electricity or compressed air and used to dig tunnels. Every combination imagineable. The tracked versions apparently took over quite quickly from the rail-mounted ones since they were so much more versatile, though rail mounted ones were still made for many years too.

[crueby]

A few pictures from one of the catalogs....

[Craig DeShong]

Sounds like a mutual admiration society kind of thing.--I marvel at what both you guys are doing.---Brian

 

[ddmckee54]

Chris just posted a couple of pictures that show fairly well how railroad shovels worked, and it's my understanding that's what this thing was originally. 

You lay the rails up to the work-face, run the shovel up to the face and dig until you can't reach any more.  Then you lay more rail and do it over again.

It was never meant to turn on a dime, just follow the rails.  The curves in those rails had a fairly large radius, even in a construction area.  So the angles machined into the tires on the wheels were all the differential that was, and still is, needed by the railroad.

Don

[crueby]

Chris just posted a couple of pictures that show fairly well how railroad shovels worked, and it's my understanding that's what this thing was originally. 

You lay the rails up to the work-face, run the shovel up to the face and dig until you can't reach any more.  Then you lay more rail and do it over again.

It was never meant to turn on a dime, just follow the rails.  The curves in those rails had a fairly large radius, even in a construction area.  So the angles machined into the tires on the wheels were all the differential that was, and still is, needed by the railroad.

Don

Great description Don. Yup, this shovel was originally built in 1906 as a rail mounted shovel, then in 1923 it was converted using a 'kit' from Marion to continuous tracks, driven at the front pair and steered with the rear pair. I would imagine that with the tracks they could turn sharper than on rails, but that is a guess.
 

[crueby]

And with a coat of paint (I went with black, that is what the originals had) on the drive sharft parts, and after cleaning out the paint that got into the shaft holes and keyways....


A few shots of what it looks like assembled on the model:



And as proof that it works (I know it would be asked for), a quick video of the bits turning. The crankshaft is not made, so this was done by turning the hoist drum gear by hand. Once the crankshaft is on, that will reduce the ratio down even more - from crank to track is a little over 20:1 gear reduction.
<a href="https://www.youtube.com/watch?v=WQM2IQTji3k" target="_blank">http://www.youtube.com/watch?v=WQM2IQTji3k</a>