nonjic Posted February 7, 2009 Share Posted February 7, 2009 Frosty, The accumulators can be sealed bag types, no maintenace required. You would have some accumulators on the pump side aswell for the 'working' oil. The valve would be a spool type, but small. With mechanical links you can get the hammer to auto cycle. Quote Link to comment Share on other sites More sharing options...
Frosty Posted February 7, 2009 Share Posted February 7, 2009 Auto cycle is what I was wondering about. This puts the device back to the steam or Kinyon type valving and control systems. More complex than a self contained like a Massey, etc. I really prefer simple when I can get. I understand simple. . . Sort of. Thanks John. Quote Link to comment Share on other sites More sharing options...
Warren Nakkela Posted February 8, 2009 Author Share Posted February 8, 2009 John: Since the piston rod on the Massey hydraulic hammer has a visible spring when the hammer strikes, there must be pressure driving it the full stroke. Therefor there is pressure in the accumulator even when the hammer is at rest. This pressure must be charged into the accumulator and because of the nature of piston seals there needs to be a provision for makeup oil as well as pressure. Does the design allow for automatically keeping up pressure and makeup oil? Warren Quote Link to comment Share on other sites More sharing options...
nonjic Posted February 8, 2009 Share Posted February 8, 2009 warren, when the piston rod lifts it additionally compresses the gas in the accumulator bag, that then pushes it back down when the oil is released below the piston. Accumulators are 'pre charged', think of an inflated balloon at high pressure, in a gas cylinder. Quote Link to comment Share on other sites More sharing options...
Warren Nakkela Posted February 8, 2009 Author Share Posted February 8, 2009 John: Thank you. Warren Quote Link to comment Share on other sites More sharing options...
Warren Nakkela Posted February 8, 2009 Author Share Posted February 8, 2009 Frosty: There are Hydraulic/steam/air that auto cycle. Steam pumps for example. Why am I telling you this? The problem arises on power hammers when the bottom reversing point is changing as iron is drawn. The top reversing remains constant so there is no problem there. Or can be easily adjusted. On the hydraulic hammer under discussion there may be one constant that may be used to trigger the upward motion and that is when the oil flow from the accumulator stops. Possibly there is a valve that would sense this and to cause the oil from the pump to raise the hammer. John and Frosty: Any ideas? Warren Quote Link to comment Share on other sites More sharing options...
Shane Stegmeier Posted February 9, 2009 Share Posted February 9, 2009 Another diversion from the main line of thought... John just how much money would have to fall into my lap to be able to afford a brand new Massey??? Just in case;-) Quote Link to comment Share on other sites More sharing options...
Frosty Posted February 9, 2009 Share Posted February 9, 2009 If it's a self contained pneumatic hammer the tup follows the compressor piston and it doesn't matter much if the tup stops before the compressor piston has finished it's power stroke. Even in the large hammers peak psi is typically in the 15lb/sq/in range and operate at around 11psi. So bottoming the ram on the anvil is zero concern. Bottoming or should I say topping it out against the end of the cylinder on the other hand can have catastrophic consequences. Okay, that's a master slave system, it's a lot different for the old steam or modern Kinyon type utility hammers. These operate off a constant supply of high pressure steam or air so there's nothing to automatically reverse the stroke. There are a number of schemes for controlling the pistons on external air hammers from electronic to mechanical and I haven't looked into any of them so I can't render an opinion on specifics. I have used a couple though and they seem to work just fine, even adjusting to the changing steel thickness automatically. At the couple I've tried do. A hydraulic hammer would have to have some good pressure bypass valves to prevent damage. After that, whatever reciprocating valving you use with should work fine. Frosty Quote Link to comment Share on other sites More sharing options...
Warren Nakkela Posted February 9, 2009 Author Share Posted February 9, 2009 No pressure bypass should be needed if all we are talking about is accumulator pressure. You can't dump accumulator pressure or you start over. Warren Quote Link to comment Share on other sites More sharing options...
Frosty Posted February 9, 2009 Share Posted February 9, 2009 Really? What happens when you spike the pressure higher than the system can take? Bypass psi is set higher than the accumulator psi. the accumulators never lose a lb. Frosty Quote Link to comment Share on other sites More sharing options...
nonjic Posted February 9, 2009 Share Posted February 9, 2009 We dont make new Massey's any more, they cost to much to make. Ive got the technology though but you would need to be thinking in the order of 5x the cost of a new chinese / turkish self contained. On autocycling of steam, or hydrualic hammers you have 2 spool valves. The control valve which is acutated by a mechanical arm from the hammer tup, and a throttle valve, which effectively limits the qty of air / steam / oil entering the control valve (thus giving blow energy or length of stroke (the 2 arent mutually exclusive - you operate the throttle valve, the hammer tup operates the control valve Quote Link to comment Share on other sites More sharing options...
Warren Nakkela Posted February 9, 2009 Author Share Posted February 9, 2009 Frosty: Certainly hydraulic systems must have overpressure protection. But it should probably never trigger when you have a constant load. (Hammer weight plus accumulator compression) when you lift the hammer. The problem with preset auto cycling is that at times you will never reach the bottom trigger point as a result of thicker work and tooling (punches,spring fullers etc.) The hammer will never know when to start up. If the trigger point is set too high and it reverses as the hammer is still falling, then you will overpressure and the relief valve will bleed off pressure. There must be a means to trigger the hammer lifting cycle only after the blow is struck. Otherwise operate manually. Warren Quote Link to comment Share on other sites More sharing options...
Warren Nakkela Posted February 9, 2009 Author Share Posted February 9, 2009 Frosty: Under what conditions would the oil above the piston (accumulator pressure) become excessive? (Piston failure) Still that pressure cannot exceed lower relief valve setting. Warren Quote Link to comment Share on other sites More sharing options...
Frosty Posted February 9, 2009 Share Posted February 9, 2009 Which type hammer are we talking about? The one John described? If so then there wouldn't be. You'd still need a bypass on the retract side though. While the solution is elegantly simple I have to admit I stopped considering about that particular scheme for a couple reasons: The valving scheme is more complicated than a self contained hammer. Same basic control system as a modern utility hammer with the addition of several extra components not necessary in a pneumatic. The accumulator spring wouldn't provide much additional ram speed and a drop hammer, even one with a boosted fall isn't in my game plan. I spent nearly 20 years as a driller and we used drop hammers to sample with. I guarantee even the 340lb hammers don't hit as hard as a 25lb mechanical and about the fastest you can cycle one is 55-60bpm. Drop hammers are in my estimation slow and punky until you get in the couple ton range. For just those reasons, if I were going to build a hydraulic power hammer I'd try adapting a self contained pneumatic type hammer to the task, and that's where my head was at when I made that reply. Frosty Quote Link to comment Share on other sites More sharing options...
NeatGuy Posted February 16, 2009 Share Posted February 16, 2009 This is not quite my idea of a power hammer but it is nicely made and an interesting tool. brad Quote Link to comment Share on other sites More sharing options...
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