Caterpillar 12 grader engine is dead - please help?

[Birken Vogt]

I recently discovered that VFD converters are available pretty cheap, mounted one semi permanently in a 3 hp blower machine I have. Not the usual VFD derated for single phase input but an actual unit by Hitachi that has 2 inputs and 3 outputs and can do soft starting and vary speed if you are into that sort of thing but without all the bells and whistles of a fancy VFD.

 

[Entropy1]

I love VFDs. I put one on my little benchtop lathe. Swapped out the original 3/4 HP single-phase motor for a 1-1/2 HP three-phase motor with VFD. The lathe now has a wide speed adjustment (without having to adjust belts) - and still has plenty of torque to make chips.

The biggest problem with VDFs is that my shop only has single phase power available - which means I need to purchase double the size VFD for the rated HP of the 3-phase motor I'm running (the whole 50% derating for single-phase input). My 10 horsepower rotary phase converter powers most my stuff. My large lathe however (pictured below) has a 40 horsepower spindle motor (230/460V 3-phase). I would need to purchase upwards of a 100 horsepower VFD to properly power my lathe with single-phase input (lots of $$$). Instead I went the rotary phase converter route (twin 40 horsepower rotary converters wired in parallel)

 

[skyking1]

All right so when are you and I going to go look at this 112?
I'm in the south sound but I'll travel.
We can use a tape measure and take meticulous notes and know if that scarifier is going to fit or not.

 

[Delmer]

Nothing wrong with a rotary phase converter, or a static converter either. I don't have a bunch of big machines like that, so I use a few capacitors here and there, some manual start, some with a hard start kit relay from an AC. And a cheapo VFD for an attic fan, full speed for blowing the house out with the leafblower, low speed for cooling off overnight.

The idea of hydraulics running cooler at lower pressure was bugging me, then I remembered the comparison to electricity. If we are casual enough to compare pressure to voltage, the voltage/pressure drop is what causes heat, that drop multiplied by the flow is the heat loss. So voltage drop x amps, is roughly the same as the pressure drop x flow. The key is that voltage or pressure drop is based ONLY on the resistance at a certain flow, it is not affected by the absolute voltage or pressure. So a hydraulic line that has 20 PSI drop at 10GPM will have that same drop and produce the same heat whether it is operating at 40 PSI or 4,000PSI. Likewise an electric line that has 5V drop at 200A will produce the same heat at 12V or 20,000V (more importantly to the 12V system, the delivered voltage will be 7V vs 19,993V, or 42% loss vs .025%) That's only one factor in electrical losses, possibly even less important in hydraulics, I have no idea.

 

[Entropy1]

The 112 grader is in Kitsap County WA. The guy selling it has recently stopped responding to texts or e-mails (I'm worried the guy might be in jail). I suspect the grader ultimately belongs to his dad (family business). They do logging & construction. He told me they used the grader about 3 times per year for maintaining the access road to their property - until it broke down. If I can't get ahold of the guy, I might attempt to contact his dad. I looked at the property on Google (satellite view) and could see a yellow grader parked next to some old trucks & shipping containers. I'm hesitant to drive out to the property unannounced (I don't want to get shot). I'll keep you posted. All I'm after is a scarifier attachment (provided it fits my CAT 12). There are still a lot of unknown variables - mainly his sale price (which was never discussed).

I'm willing to fabricate a scarifer attachment, but I'd much rather purchase one.

 

[skyking1]

Sure thing. I drive through Kitsap county from my house to our future home site so it's not out of my way.

 

[Entropy1]

The overwhelming vast majority of heat-input into hydraulic fluid happens within the pump. Line-losses (viscosity shear-forces acting along the piping's boundary layer) will technically generate small amounts of heat throughout the piping - but these line-losses remain almost trivial compared to the large differential pressure-loads placed onto hydraulic motors & cylinders (aka the machine doing work) - all of these loads are ultimately placed onto the pump.

Example: if you are putting 10 mechanical horsepower into a hydraulic pump that's 85% efficient, it means 8.5 horsepower is actually pumping the fluid, and the remaining 1.5 horsepower is lost as heat introduced into the oil. Note 1.5 horsepower is equal to about 1119 watts, or 3818 BTU/hour - this is the thermal generated-load that MUST be removed from the fluid, or you'll overheat the entire hydraulic system (think sizing your oil cooler)

Here's what's interesting. If the 10 HP pump in the above example is operating at 2000 psig, you'll generate 1.5 horsepower of heat (pump is 85% efficient). If it's running at 4000 psig (same 10 HP input), you generate 1.5 HP of heat (pump is 85% efficient). The temperature-rise within hydraulic fluid at 4000 psig will be more than it is at 2000 psig, because the fluid is moving half as fast through the pump at 4000 psig (oil ultimately spends more time getting hot inside the pump). Overall system power-performance will be nearly identical between the two operating pressures. The main difference is that the 2000 psi system will have less temperature-rise of 4000 psig, and will have a slightly larger pressure drops across the system piping (due to the increased flow-velocity). The downside with the 2000 psig system is that you need double the surface-area on your cylinders to get the same pushing force on your machine. It is understandable that excavator companies want to run very high pressures. A 6.5 inch diameter cylinder at 3000 psig will make the same force as a 5 inch cylinder at 5000 psi. There is no doubt that smaller cylinders ultimately cost less to manufacture, and small cylinders also reduce the unnecessary installed weight on the machine.

Additional notes:
AW-46 hydraulic oil has a density of about 7.2 pounds per gallon, and a specific heat capacity of roughly 0.45 btu/lbm-F (typical fluid operating temps). In the above example, 8.5 hydraulic horsepower at 2000 psig will have a pump discharge flowrate of 7.29 gpm. At 4000 psig the flowrate is half, or about 3.64 gpm. Assuming the hydraulic oil is entering the pump at 120 degrees F, the temperature of the oil existing the pump will be 122.7 degrees F at 2000 psig, or 125.4 degrees F at 4000 psig. Whereas the ultimate thermal load placed upon the systems oil cooler remains the same - 63.64 BTU/min, or 3818 BTU/hr, or 1.5 horsepower of heat.

 

[Welder Dave]

Curious if you have a larger welder than the AC/DC buzz box? It's kind of out of place with your other equipment.

 

[Welder Dave]

Double post

 

[Entropy1]

I have a Lincoln 275 welder. I mainly use it for TIG welding, however the machine can hit higher currents than the AC/DC buzz-box when SMAW welding, which is required for the larger 3/16 hard-facing rod that I have. I also picked up 1200 pounds of 9018 weld rod (also size 3/16") in unopened 50# cans - got it at auction for 250 bucks (amazing deal). It's wonderful rod, but again - the little AC/DC buzz-box doesn't have enough guts to lay it down properly. The 9018 seems happy at 210 to 220 amperes, whereas the hard-facing rod likes closer to 300 amperes (both DCEP). I've only got single-phase power at my house - thus my options for larger welding machines are very limited. If I had 3-phase power in my shop, trust me - I'd have massive welding equipment. I've passed up large 3-phase welders at auction - probably hundreds of times.

I have a Miller 350P wire-feed (set up for dual-sheld)
I have a Miller 120 (set up for sheet metal - solid core)
I have an oxy-propane torch (for cutting)
I have an oxy-acetylene torch (for brazing)
I have a small plasma cutter - will cut up to 1/2" (very slowly) - mainly use it on sheet metal.
The little AC/DC buzz-box I use the most. My rods of choice are 6011 and 7018 - mainly 1/8" and 3/32"
I have an oven in the shop for keeping the low-hydrogen rod dry.

I reskinned the bucket on my Komatsu with 5/8" plate and hard-faced it (below pic). The original plate was worn paper thin in several spots. I used regular mild-steel (didn't have anything stronger at the time). It came out pretty good. Komatsu makes their buckets a little funny. They layer a bunch of thinner plate together, in lieu of using one solid piece. I was through all the layers, and down to the last one. Apparently the layering technique results in less bucket noise on the construction site (deadens the acoustic ringing of the bucket from impact). Well, i suppose now my bucket is loud. . . .

My friend with the recycling yard acquired some 3/8" thick DH-36 steel plate, and several nice pieces of HY-80 (1/2", 3/4", and 1" thick). It was scrapped by Vigor Marine - presumably left over plate from one of their contract jobs. I purchased a bunch of it. The rod of choice for welding HY-80 is 11018, however the 9018 will give satisfactory results - with the proper preheat. My biggest complaint about the 9018 (3/16) is that the slag falls right off the weld when doing overhead. Honestly it's hard for me to keep the slag over the weld when vertical welding. For me it's pretty much a horizonal rod - even though it's marked all position. For out-of-position welding I use 1/8" 6011 or 7018 (or the wire feed)

 

[OzDozer]

Man, you've got enough equipment in that shop to restore steam locomotives. A Cat grader with a few problems is going to be a walk in the park for you. How long is that lathe bed? - and did you have many problems setting the bed for accuracy?

 

[Entropy1]

The lathe bed is just under 20 foot. It weighs about 25,000 pounds (weight estimated by the crane operator). The lathe was manufactured in 1960 and was originally owned by the US Navy. The Navy donated to a community college in the 1980s. The college wired it up and it sat forever unused. They wanted to offload it to make room, so I purchased it from the school (at auction) for $3,200 bucks after tax. It cost me an additional $2,500 cash to get home. The guys who transported it home complained that they underbid the job (which they did) - so I tipped them 400 bucks.

We set the headstock-end down onto the concrete (on top of equipment skates) and set the tailstock end onto the dirt. Then we picked up the tailstock-end and rolled the lathe into the shop. Right about the time the crane's tilt warning lit up, we had it where it needed to be. As far as leveling. It's pretty close. I need to get a machinist out to my house with a precision level and have him dial it for me.

 

[Welder Dave]

I was reading an article about navy ships and never realized they had a full compliment of large machine tools and a machine shop(s) on board. A lot of the machines are like new when the ships are decommissioned. They usually sell for pretty reasonable but getting them out I think would be the hardest part.

 

[OzDozer]

Dave - Yes, the ships engineers will even do major engine rebuilds in mid-ocean - including big-end bearing reconditioning, in-situ! There's some great videos and documentation on the 'net of the work they carry out, it's amazing what they can do.

 

[JaredV]

This thread just keeps getting better. First one old grader, then the possibility of a second, then cool home built shop equipment, then a couple old mills and a great big old lathe! Plus interesting electrical, hydraulic, welding and repair chatter.

 

[Entropy1]

Here are some pictures. Ignore the date-stamp - I just took these about 10 minutes ago (I skipped the formatting of the camera)

I'm thinking that the entire injector assembly is not missing - but rather just the top portion. My little camera has a diameter of 7.9 mm (0.311 inches), and I was unable feed into the main 4.5" combustion cylinder - I got stuck at the bottom of the injector opening. The pictures are posted below from outside moving inward.

 

[Entropy1]

And further in -

I might be looking at the top of the piston, but I'm clearly not inside the cylinder like I hopped I'd be. I can't see the cylinder walls. Camera gets stuck about 2 inches down the injector hole.

 

[Entropy1]

And here's my crappy exhaust pipe (the one you must cover with a soup can to keep rain out).

I was able to feed it down to the bottom of the main exhaust manifold. I didn't attempt to push the probe any further. I don't see any rust in the bottom of the exhuast manifold, but that doesn't really mean anything. It only takes one good rain event (with the soup can removed) to size the engine. . . . .

Again, ignore the date stamp on the pictures - I just took these today (skipped part of the camera setup, and got right to it. . . .)

 

[OzDozer]

The precombustion chamber is still in position there - what is missing, is the capsule injector, the retaining nut for the capsule, and the injector line.

If the exhaust pipe is open to the weather, rainwater will have travelled straight through to the cylinders that have valves in the open position. The water will gradually drain into the crankcase, but the cylinder walls will corrode rapidly in the presence of heavy moisture.

 

[Entropy1]

Well crap. What do I do next? I might be looking at the top of the piston, but I'm clearly not inside the cylinder like I hopped I'd be. I can't see the cylinder walls - to see if water had gotten it and siezed things up. The camera gets stuck about 2 inches down the injector hole. The exhaust inspection really didn't tell me anything either.

Maybe I should soak the cylinders in WD-40 for a few days, and then try to bar it over?