New to me Michigan loader

[oldseabee]

The 675 had a single articulation joint, twin 1710 Cummins engines with convertors feeding one transmission, 4 10 1/2" boom cylinders, boom and bucket weighed 20 tons each, bucket to boom pins over 200 lbs. each. Nice machine to work on, lots of room and every thing needed either a come along or the service truck crane to put it in place.

 

[RonG]

I Googled the Trojan 8000 and although I cannot find any pics yet the hits I did get made reference to dual articulation and I have the feeling that the machines were made back in the '60s so I will keep looking.Ron G

 

[oldseabee]

The 8000 Trojan did have dual articulation, There was a 6 ton center section with steer cylinders on each end. the claimed advantage was smaller turn radius and that in a full turn with a loaded bucket the center section acted as a counter weight give a higher tipping weight stability. it was an 8 yard machine with 480 HP either Detroit or Cummins engine. came out in 1966.
675 loader had 24 yard bucket or a 36 yard coal/chip bucket.

 

[Ryan151]

Sea bee I need to get with you on my 275b I have a delay in part of the controls. Its. Serial number is 425b-427 I think it's a 1974 but the bucket curl back has a delay long enough you can really rock it in and out to get a heaped load fast. I'm also thinking my hydraulic system accumulator is out because the machine seems to "slam" when you are booming up and kick the lever out of detent or are un curling the bucket it seems to slam what are your thoughts?

 

[Ryan151]

Sorry typo.... Can't rock it

 

[oldseabee]

A couple of things, 1 the hydraulic pump is 2 stage, both sections pumping give you 81 GPM at below 1500 RPM and1200 PSI, at 1800 PSI and above 1500 RPM the rear section goes into bypass so now you have36 GPM and at 2000 RPM and 2000 PSI you get 48.5 GPM. so if the pump dosn't bypass you have very high flow which will give you the slamming effect. That said, the main control valve is a split spool valve made by Husco, that means that one spool sends oil to the cylinder and the other one opens to send the return oil back to tank, this all is controlled by orfices so it happens all at once and the boom or bucket will move smoothly along with the proper oil flow, I have moved so some of my stuff is in storage, I'll have to go and dig it out for more specific info about how to do the testing.

 

[kshansen]

A little off topic but years back we had an old 275 Michigan that was no longer needed at another plant and as at that time we were the central repair shop for the state it was parked at our quarry. It was used off and on as a spare machine until it developed a strange problem.

As I recall the boom would go up and down fine but bucket would not roll back. That is unless you reved the engine up to high idle then bucket would move good at least till you tried putting a slight bit of down pressure on the cutting edge. As this was a machine we really did not need no one wanted to have us spend any time diagnosing it let alone spend a penny to fix it. So the machine was parked up on what was referred to as "Treasure Island". A couple years later upper management decided to send some surplus jewels to auction and this one was one of the ones going. As it had set for at least two years with batteries still in it there was no surprise they were dead as dead can be. But after hooking up jumpers to it for a bit that old Cummins started and ran like it was just parked over night. Also not surprising it still had the same hydraulic problem. As we needed a large machine to push and tow some of the other auction jewels around that day we kept it running. One surprising thing was after running most of the day the next morning those old batteries actually took and held a charge. It was taken to the auction site and continued to be used as a tow machine for the next couple weeks never failing to start.

I did come up with a theory that I would have loved to check out but never got the chance to investigate as to what the problem was with the roll back. My theory was that one of the nuts(or what ever held the piston on the rams) had backed off allowing the piston to come off the ram and at low RPMs the oil would by-pass the piston through the hole in the center. However when engine was reved up enough the flow of oil was enough to push the piston back on the ram effectively sealing it again. As the surface area of the piston would be greater than that of the end of the rod the pressure would keep it in place until you happened to apply any down pressure then the piston would slip off the ram an the oil would bypass through the piston center hole.

Shame as it would have been a simple thing to check just by unhooking a couple hoses on the cylinders and start engine with them poke in to a drain tube and try to roll back the bucket at idle watching to see which one the oil was by-passing through. There might be some other explanation but that is the one that seemed to make sense to me and it did bug me that I was not able to test it and fix it. Hope who ever did buy that one figured it out and fixed it would have been a good machine for a small two man gravel pit operation. It was a bit rough around the edges but was a strong working machine.

 

[oldseabee]

Makes sense to me, a less messy way to see which one is bad would be to take a piece of 3/8" pipe and use it like a stethoscope and listen to one of the cylinders while someone moves the bucket lever back and forth, you should be able to hear the piston slap. Also could be a bad port relief, try swapping the bucket hoses to see if the problem moves to the other direction which would sort of take the cylinders out of the picture and make the valve more likely, you didn't say if that loader was a "B" or IIIA, different valve set up.

 

[RonG]

I ran a 275 one summer loading a fleet of trucks and it had a 335 Cummins in it and was a very powerful machine.The reason that I am posting is that I was surprised that it did not have a Detroit in it as it seems that every other Michigan I had been around Detroit seemed to be the preferred power plant.Ron G

 

[oldseabee]

I think that Cummins was over the whole country was the majority, mainly what the local dealer preferred is what they pushed and some of the big Quarry customers like Vulcan Materials would spec the large machines with Cummins.

 

[RonG]

It is difficult to find fault with Cummins as much as the Detroit was liked for reliability.I am from a cold climate and the Detroit has a reputation to start if it will turn over as long as you have laughing gas to humor it a little and you often don't need that but no one wants to take a chance of it turning over twice in a row.
They say the new Detroit 4 strokes are pretty good too.Ron G

 

[Ryan151]

I went ahead and bought the relief valaves for the pilot valves. Super cheap on minnpar so I figured what they heck. The machine will slam a lot harder if the engine is revved up while booming up say... I will note this the engine does bog down a lot and the machine Just doesn't seem to be very powerful when it comes to digging. Howerever it's very strong as far as push and travel speed but when you start booming or curling when in first gear digging pedal to the floor it really Boggs down. I thought it was a fuel issue. Put new filters on and also adjusted the throttle linkage to make sure it was getting full fuel and I still have the same issues. Seems now like it all makes sense I'll read my service manual but any tips you have sea bee would be great. Thanks again and sorry to hijack the op

 

[oldseabee]

As I mentioned in my earlier post, the hydraulic pump is 2 stage, one section should dump to tank at about 1800 PSI, if it doesn't you are trying to pump over 100 GPM at high pressure instead of 48 GPM which will load the engine a lot more and all that extra flow will cause things to slam and pop the reliefs. There are two styles, the early version had the control valve on top of the pump and would dump the front section at 1800 PSI, the later style had the control valve built into the center section and would dump the rear section of the pump, in either case there is a test port and a relief adjustment and another test port to monitor the section that is supposed to dump to see when or if it is dumping, machine has to be above 1500 RPM and above 1800 PSI to check the dumping point or if it is dumping at all. to do the test, bottom out the bucket rollback at low or just above then raise the RPM, the pressure on the dump should drop off at about 1500 RPM, if it doesn't drop off there is an internal problem. You can open it up and look for something obvious, (There have been stuck spools in these pumps.) or take the pump to a Tyrone hydraulic shop or any good shop.

 

[Ryan151]

Okay thanks sea bee. Thankfully I have a service manual too I'll diagnose this stuff next chance I get. I'm thinking though as bad as it Boggs the engine down and as hard as the slam is this has to be what's going on.

 

[Ryan151]

If in fact the pump is bad do you have a pump shop you recommend?

 

[oldseabee]

Motion&Flow Control
299 Bryant St., Denver, Colorado 80219
303-762-6527
They are Tyrone dealer, don't know any thing about them but seem to be pretty big in that area.
By the way the relief valves in the pilot valve are port reliefs for shock loads, the main relief is in the big valve.
Another caution, put a vaccumm pump on the hydraulic tank or drain it before messing around with the main valve or you may strike way more oil then you can get in a bucket.

 

[Ryan151]

Yeah i usually drain the tank first. At least lower than the pump if I'm working on the pumps but I suppose a vacuum tool for a radiator would work if you knew it would be a quick easy job. What would you say is the cause for delay in my controls? It has a delay for the bucket curl in. I'd say about 1 second delay

 

[oldseabee]

There are several choices, 1. air in the system can cause a delay, factory suggests do 3 full cycles of both boom and bucket at hi free idle to clear any air out of the cylinders, 2. anti void poppet stuck open in the main valve allowing either air or a vacuum into the system, 3. trash in one of the flow restrictors in one of the bucket spools. The first is easy, the others mean opening the main control valve. One other possibility is a faulty cap on the hydraulic tank, this is either a 7 PSI or 14 PSI pressure cap that helps squeeze air out of the oil mainly to prevent cavitation in the pump, air can collect in the higher end of the cylinders.

 

[Ryan151]

Hmm. It is only in the bucket curl back not curl out or boom up or down only in that one control

 

[oldseabee]

There is one restrictor in each spool for the bucket cylinder , the only thing I can think of to be sure is to open up the main valve and pull the spools out and check for a blockage in the restrictors. What I would do OFF BOOK would be to reverse the bucket hoses at the pilot valve to reverse the flow and maybe blow the trash out. Other wise you have to decide if it's worth all that work to save that second,or wait to see if it gets worse.