Got one I haven't been able to answer. Topic is a Dual tilt dozer set up on a D6D 4X6608-up with 44E15,300-up angle blade. Here is the parts diagram and basic schematic. Rod end of cylinders are tied together. Question is how is the common line charged and maintained? I suspect the spring loaded check valves and relief/makeup valves in the control valve (open center hydraulics) have something to do with it by I don't have any service manual information to verify how it works.
OM the head ends of the rams are looped so both rams move equal amounts and don't get out of sync causing the top of the blade to pitch forward resulting in a snapped blade centre pin. There was a cat service magazine that told all about this somewhere back in 83-84. I know because I saved the SM. But I would have to do some searching to find it, was quite a few moons ago
Hi Marv and thanks. I'm having a hard time getting my head around this circuit. If the heads are looped, how is this done. I don't see anything unusual about the porting on the 4-way control valve or extra lines besides what I show in the parts diagram. Sure would like to see some hard copy and schematic for this arrangement. Do you know if it is described in later service manuals. Seems it's still a current approach but not in my old stuff literature.
Have you got a picture of the tilt cylinders innards? Wondering if the pistons don't have end of stroke valves that open up, can't see any other way to purge that loop.
The System Operation for dual tilt is pretty brief but it won't make sense to post the text here without the cutaway diagrams of the control valve that go with it. Drop me a PM with your email address and I'll send it to you.
The dual tilt for bullblades is a whole different animal Nige The angle blade setup effectively makes them each a single acting ram; the heads in a loop means that as one ram extends it pushes its opposing mate backwards the same amount. The angle blade cannot pitch backward and forward; otherwise it snaps the centre pin. The A blade tilt rams have relief valve in there pistons so when each end bottoms out the oil flows into the looped heads to fill the circuit. Is a cat service magazine march 8 1982 that talks about it. yes once upon a time many many moons ago I worked for the NZ cat dealer and got all this info; even had a Cat service training passport too ! Anyway kept a lot of the service mags from 80 to 86 that pertained to D4s -D8Hs just incase maybe one day this boy owned one ! cheers :drinkup
Merv, I was looking at the dual tilt setup for a 163 hydraulic control as fitted to an 04X-prefix D6D. Are you saying that's not how it works...? Found the March 1982 Service Mag online BTW. When OM gets in touch I'll send it to him as well.
On a bullblade the dual tilt pitchs the whole blade backwards and forwards. Or one ram extends to tilt blade sideways. Angle blade does not work like that. Pitch is static. One tilt cyl extends, the other retracts; so blade tilts over to one side or the other.
Hi Nige, PM is on its way. Think I have it figured out. The answer is in the control valve. Anxious to see the info. Thanks
Hi, There are no relief valves in the pistons.
The Service Magazine article indicates that there is a new LH Tilt Cylinder Group 1U-3496 that replaces the former 7J-3171 Cylinder Group which was cancelled. The former cylinder group could be modified to the latest design by installing a ball check valve in the housing. OM, email on its way.
Got it, thank you very much. Also got the service manual info for a dual tilt D7E. Between the two I think I have it figured out. Marvels of the internet!!!!