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[Grayco]

You sound busy.  That 22 pound weight has to pull a vice along two rails. There's a lot of resistance there to overcome. You might need less.

I was thinking the same thing.  With set up, gravity will be pulling the rock and vise into the blade and there are no slides so I'll start light.  What kind of feed rate should I be targeting?  My test rock will probably be a piece of quartzite.

[55fossil]

   Make sure you have a GFI plug on there somewhere. I never trust GFI breakers and use a plug close by.  good luck

[Ranger_Dave]

To find the right amount of weight, I put a piece of mariposite in the vice and attached the hand scale I used to weigh llama packs with to the cable. The scale has a hook on one end, a handle on the other, and the scale dial in the middle. I think it started out as a scale to weigh fish.  I started the saw and pulled. At 22 pounds it was cutting nicely and it didn't sound like the motor was bogging down. Then I put 22 pounds of sand in an old paint can and hooked it up. Works great.

[Grayco]

Progress update;
I have cleaned this saw up and discovered the spindle bearings were bad, so I replaced them.  I do believe this saw was homemade but the builder was a talented craftsman.  He was certainly a good machinist but I suspect he was an industrial mechanic as well.

I found Babbitt between the spindle bearings.  There aren't many folks who would even know what Babbitt is, now days.

The spindle/vise support assembly was installed with the long side on the outside of the box. That did provide more room for the vise to adjust, but it made it nearly impossible to align the drive belt.  I mounted the assembly with the short side out.  The belt lines up easily and I think it looks better.

The blade fender was made of brittle plexiglass and broke apart.  With the spindle/vice support mounted differently, the location of the fender no longer works.  I will probably forget the fender for now and work on a cover to cover the whole box.  The box is 12" x 18" so I may luck out and find something that is the right size and can be easily modified to work.

I believe if I remove the bolt on the vise that keeps the vise from rolling to the bottom of the box, I will be able to roll the vise below the level of the top of the box.  This will allow me to set a flat top on the box and use this as a trim saw too. That is when I will need a blade fender.

I have a plan for a feed mechanism.  Gravity feed is a good option, but with this saw I only need to rotate a shaft 90 degrees to get a full cut.  My current plan is to put a bicycle sprocket (about 3") on the lock collar just behind the handle and use a chain attached to an extension spring to rotate the vise.  I think I can select a spring that will provide about 20 pounds pressure to the cut and decrease pressure as the cut nears it's end.  Time to scrounge parts.  For now this saw is going on the shelf and I have started cleaning up my 20" saw.  I am going to start a new thread on it.

[Slabbercabber]

What is that mass hanging underneath?  Could that be a rotary sludge separator?  If the spring idea doesn't work out, there are dozens of sources for small gearmotors.  Barbecue and Erector set motors come to mind.

[Grayco]

What is that mass hanging underneath?  Could that be a rotary sludge separator?  If the spring idea doesn't work out, there are dozens of sources for small gearmotors.  Barbecue and Erector set motors come to mind.

The mass underneath is an oil reservoir.  I described it with pictures in my post titled 20" saw project. I posted that yesterday.

As far as the drive system, this saw had a BBQ motor mounted on it.  The whole system was ugly and funky and was not complete. (see the earlier pictures).  Keeping in the spirit of keeping it simple,  I really think the spring and chain system will be cleanest.

[peruano]

In response to your query as to a desired feed rate, I'd guess that most slab saws are aimed at 4-7 minutes per inch.  Slow is good in terms of blade life and motor life.  Many folks who hand feed trim saws or tile saws in trying to cut slabs (or anything more than trim) probably crowd their blades excessively (its too painful to go real slow).  I"ve used a water bottle as a weight and can easily adjust weight as needed.  I'd start with a small and probably soft rock to get a feel for how it cuts and the proper setup.   
On  a separate issue, the Model T rock rascal is a common trim saw (and combo unit).  Pictures should abound.  I have posted one that I'll have to look for the url.  The wheel for the grinding end is a 6", but I believe the water tray is a bit narrow for an expand wheel which would be ideal, but I'd check that as a possibility. 
I borrowed a small motorcycle fender for a blade shield for my homemade saw, but a bike fender would work as well. 

[peruano]

Here's a Model T with a narrow wheel on it.  I fabricated the belt guard.