My waterjet operates at 50,000 psi. Keeping the system sealed is an ongoing battle. I find it remarkable that you got your parts to seal up to 8000 psi. Well done.
As I said in the video high pressures can be very difficult to keep leak free and that is why I did not go any further in pressure. Also my gauge was near it's upper limit. Wow 50,000 psi I would bet there would be no flexible hoses to hold that pressure.
My thought on the failure: your o-ring groove appears to be square in cross section. That will form a stress riser. At the break, the iron appears rather coarse grained. You mention the iron is rather soft (ductile). Under load, the cap flexed (dished outward). The combination of coarse grain and the stress riser under the influence of that load flex gave rise to a point failure, which cascaded through the lattice until the flexural stress was relieved by structural failure. The rigidity of the rotor iron resisted "dishing". I would love to see the soft iron caps replicated with a full radius bottomed o-ring groove to see if they would still fail at roughly the same pressure, higher pressure, or survive to the pump limit like the square grooved rotor iron caps
Sharp corners are great stress risers in iron castings but what puzzles me is both castings had those square grooves and yet only one failed. I was surprised on how high the pressure the soft casting went to.
From what I see with the pressure you put into the cylinder, and as thin as those castings were at the machining groove for the o-ring, there is nothing wrong with them. They are cast perfectly and if they were a little heavier/thicker at that point there would be no issue with them. Looks like a job well done.
One failed and one did not. This just might be an example of the fact that normal gravity casting methods can lead to a wide spread in casting properties. Anyone who has worked in the industry can attest to it being perhaps one of the more frustrating parts of foundry work that even with the same techniques and same materials results can vary widely batch to batch and indeed even within the one batch with no obvious reason why. I can all too personally attest to this sort of thing being the bane of a foundry metallurgists life 😥. The use of sawdust is interesting - how do you feel it compares to coal dust, and how fine was the sawdust. Also have you tried something like corn or wheat flour? Luddite's suggestion about a more rounded bottom to the o ring grove bears thinking about, but it may only amount to "tinkering at the edges".. Martin
Both those covers were poured from the same crucible and yet only one failed. Sawdust seems to work really well with iron. I have tried wheat flour by dusting it on the mold but not mixing flour with the sand. The result was a discolored surface on the iron so I never bothered to use it again. Before I retired I used to replace O rings all the time and the grooves were always square and some O rings were square in cross section.
I found that that last batch of rotors that I tried melting, I went to cut up the stuff that was stuck in the crucible and it sparked out like steel, nowhere near like cast iron, so I would be careful of the type of rotors you use. The ones I used were very large, and I have no idea what they were off of, but they froze the melt and I ended up with some sort of crucible steel stuck in the crucible. Smaller ones off of cars have seemed to be ok tho.
All the 12 threads for the covers were so easy to tap the threads ( 5 mm taps) The covers had some slight chill on the edges so the speed was slowed down and was no problem machining them.
I am amazed that you can get those kind of pressures out of that pump and have the hose survive as well. My question, however goes to something else. Based on your videos I am now wanting to move on from casting aluminum and bronze to trying my hand at casting cast iron. I am running into an issue with finding coal dust. I've spent hours on google trying to find a US supplier of coal dust so I was wondering about using the sawdust flour or perhaps finely ground charcoal briquettes. Do you have any thoughts on what would work best if coal dust is not an option? Thank you, Jim
I was amazed as well but this time around the grease pump was struggling to get past 550 bar (8000psi). If you watched my last video on pressure testing the hose burst but this time I had two leaks on the threaded fittings. As the gauge maximum pressure is 600 bar (8500psi) I decided not not go to a higher pressure. You do not need to use coal dust for iron castings, If you don't use coal dust it just takes a little bit longer time with a wire brush to clean the sand of the casting. Charcoal dust does not work but if you use sawdust it will burn and lift up the iron and prevent it from sticking to the surface.
My waterjet operates at 50,000 psi. Keeping the system sealed is an ongoing battle. I find it remarkable that you got your parts to seal up to 8000 psi. Well done.
As I said in the video high pressures can be very difficult to keep leak free and that is why I did not go any further in pressure. Also my gauge was near it's upper limit. Wow 50,000 psi I would bet there would be no flexible hoses to hold that pressure.
My thought on the failure: your o-ring groove appears to be square in cross section. That will form a stress riser. At the break, the iron appears rather coarse grained. You mention the iron is rather soft (ductile). Under load, the cap flexed (dished outward). The combination of coarse grain and the stress riser under the influence of that load flex gave rise to a point failure, which cascaded through the lattice until the flexural stress was relieved by structural failure. The rigidity of the rotor iron resisted "dishing". I would love to see the soft iron caps replicated with a full radius bottomed o-ring groove to see if they would still fail at roughly the same pressure, higher pressure, or survive to the pump limit like the square grooved rotor iron caps
Sharp corners are great stress risers in iron castings but what puzzles me is both castings had those square grooves and yet only one failed. I was surprised on how high the pressure the soft casting went to.
Great to see a new video about casting from the Master
Wow cool video 👍🏻
From what I see with the pressure you put into the cylinder, and as thin as those castings were at the machining groove for the o-ring, there is nothing wrong with them. They are cast perfectly and if they were a little heavier/thicker at that point there would be no issue with them. Looks like a job well done.
Yes you are so right, a little thicker it would have survived the high pressure.
One failed and one did not. This just might be an example of the fact that normal gravity casting methods can lead to a wide spread in casting properties. Anyone who has worked in the industry can attest to it being perhaps one of the more frustrating parts of foundry work that even with the same techniques and same materials results can vary widely batch to batch and indeed even within the one batch with no obvious reason why. I can all too personally attest to this sort of thing being the bane of a foundry metallurgists life 😥.
The use of sawdust is interesting - how do you feel it compares to coal dust, and how fine was the sawdust. Also have you tried something like corn or wheat flour?
Luddite's suggestion about a more rounded bottom to the o ring grove bears thinking about, but it may only amount to "tinkering at the edges".. Martin
Both those covers were poured from the same crucible and yet only one failed. Sawdust seems to work really well with iron. I have tried wheat flour by dusting it on the mold but not mixing flour with the sand. The result was a discolored surface on the iron so I never bothered to use it again. Before I retired I used to replace O rings all the time and the grooves were always square and some O rings were square in cross section.
Thanks for sharing!
Your videos and their informative content are the best.
All the best from Inverness Scotland.
Thank you.
I found that that last batch of rotors that I tried melting, I went to cut up the stuff that was stuck in the crucible and it sparked out like steel, nowhere near like cast iron, so I would be careful of the type of rotors you use. The ones I used were very large, and I have no idea what they were off of, but they froze the melt and I ended up with some sort of crucible steel stuck in the crucible. Smaller ones off of cars have seemed to be ok tho.
All the 12 threads for the covers were so easy to tap the threads ( 5 mm taps) The covers had some slight chill on the edges so the speed was slowed down and was no problem machining them.
Duh!!! Oops. Not only did I ask the same question about 6 months ago, but you also answered it. Thanks
What pressure will your cylinder be operating at when complete?
Safety margin question.
Less than 10 Bar, so plenty of safety margin !
@@chrisarmstrong8198 You read my mind!
It is only a test piece to see how strong my castings are.
The one that broke must of had a flaw, great experiment tho.
I am thinking the same thing but not having Xray equipment I cannot be sure.
@@luckygen1001 Could you slice the failed casting into strips and use dye to see if anything shows up?
I am amazed that you can get those kind of pressures out of that pump and have the hose survive as well. My question, however goes to something else. Based on your videos I am now wanting to move on from casting aluminum and bronze to trying my hand at casting cast iron. I am running into an issue with finding coal dust. I've spent hours on google trying to find a US supplier of coal dust so I was wondering about using the sawdust flour or perhaps finely ground charcoal briquettes. Do you have any thoughts on what would work best if coal dust is not an option? Thank you, Jim
I was amazed as well but this time around the grease pump was struggling to get past 550 bar (8000psi). If you watched my last video on pressure testing the hose burst but this time I had two leaks on the threaded fittings. As the gauge maximum pressure is 600 bar (8500psi) I decided not not go to a higher pressure. You do not need to use coal dust for iron castings, If you don't use coal dust it just takes a little bit longer time with a wire brush to clean the sand of the casting. Charcoal dust does not work but if you use sawdust it will burn and lift up the iron and prevent it from sticking to the surface.
did you do a normalizing heat treatment?
No I do not, all castings I pour are used as they come from the sand mold.
Is it possible that micro fractures appeared when shrinking as it cooled?
That is possible.
Reminds me of a war movie watching the meter"Tiefenmesser"...
Yes it does look like a depth gauge.
Put some grease into the chamber first next time, that way you won't run out in the grease gun.
I filled up the cylinder with oil before the grease nipple was screwed in. I should have checked the grease gun before I did the test.
@@luckygen1001 ok, I must have missed that when my kids where talking to me.
Thanks!