Revolution Gear Supply Chain Update
- Thread starter sab
- Start date
I have revolution front axles on order since early January, I spoke with them last week. They assured me they will receive parts on the 15th of this month and ship them out. I hope so don’t know if they are stringing me along to avoid canceled orders and issuing refunds.
OP
Nothing new, I will be contacting them soon for an update and will post here when I do that.
OP
Jerry - I'm curious, and I'm not familiar with the Super 35 stuff (mine is a Rubicon, so I've never look into that), but why do you recommend 1541H over chromoly? I assume it's due to lower cost because 1541H is a plain-carbon steel and inferior to chromoly in terms of tensile strength and, I assume, toughness.
OP
I hope that's true! I was going to call them next week, so I'll wait until Wednesday, the 16th, to call, and see what they say.
1541H is not a plain carbon-steel, it has special heat treating to harden its surface so the Dana 35's outer bearings won't wear through its surface. Standard Dana 35 axle shafts have this same surface hardening treatment, though the 1541H version is stronger.
The problem requiring the surface treating of the shafts is the Dana 35's outer bearings don't have an inner race so the roller bearings ride directly on the shaft, not a race.
The below photo shows what happens to a 4340 chromoly shaft, which doesn't have this surface hardening, when run in a Dana 35 axle.
Incidentally the Rubicon's Dana 44 axle shafts are plain carbon steel.
OP
Thanks, Jerry! That's very helpful, and what I love about this site - the knowledge base is impressive! I didn't realize that the Dana 35 bearings use the shaft as an inner race. That's definitely a cost-compromise design. Bearing materials trade hardness/strength for ductility. Axle shafts need strength, but also need ductility. There is a combination of these in steel properties call toughness, and axles need toughness over all (strong, but ductile.) I wasn't aware of 1541H steel until today (I've never been involved in a design where the shaft is the inner race), but it makes sense to me now. I just pulled out my steel book, and 1541H is very close in composition to 1040, with a bit more manganese and some silicon added, which makes sense because both of those address hardenability, especially surface hardness (important for bearing surfaces). The designation breaks down like this: 1541H The first digit (1) means it's plain carbon steel (yes, it really is a plain carbon steel) The second digit (5) means added manganese The third and fourth digits (41) mean 0.41% carbon (a "medium" plain carbon steel) The last digit (H) means it's hardenable to a certain depth (again, a key requirement for a bearing surface) |
The basic difference is one is a through hardening alloy and the other is more suited to case or surface hardening. You can get the 4xxx series alloys up to a hard enough surface for the bearing but then you lose a lot of ductility which takes a good heat treater to get some of that back and maintain the surface hardness needed for a bearing to ride on it. Most won't do that so the 1541 makes a better choice since it is easier to case harden.
OP
Agreed, the chromoly steels can be made very, very hard, but then the ductility tanks, and in one worst-case scenario, you could end up with a shaft that will shatter under dynamic impulse loads. Not a good trait (shattering in use) for a driveshaft. Again, using the shaft as the inner race is a huge compromise.
Thanks for the lesson (again), Jerry and Mr. Blaine!
Thanks for the lesson (again), Jerry and Mr. Blaine!
The ductility doesn't have to tank. I built the Superior high strength u-joint out of 4340 blanks. Then I worked with the treater to retain a high level of ductility to stop the pins from breaking off under high impact loads and still be hard enough to run needle bearing caps. It can be done.
Another of those blanket statements "using it as a race is a compromise" which isn't fully accurate since we are all familiar with needle bearings in u-joints.
OP
Suffering from insomnia again this evening (morning?)...The ductility doesn't have to tank. I built the Superior high strength u-joint out of 4340 blanks. Then I worked with the treater to retain a high level of ductility to stop the pins from breaking off under high impact loads and still be hard enough to run needle bearing caps. It can be done.
Another of those blanket statements "using it as a race is a compromise" which isn't fully accurate since we are all familiar with needle bearings in u-joints.
What I meant by it being a compromise to use the shaft as a bearing race is that it trades something (cost, packaging, assembly weight, all of the above?) for part complication (adding another mechanical property - surface hardness - into the equation).
And with u-joints, a similar compromise is made, but it's a different part, with different design parameters, so there may be a different solution that works better for that different part. We engineers make design decisions for many reasons, and we don't all think alike, so our design solutions, even for the exact same part, may be different, but if they work, they work, right?
Many years ago, when working for a US-based powersports company, we had a similar design situation for a much smaller axle (about 8" long and 0,750" in diameter) with much smaller torques in a new design under development. Under one particular real-world load case (think prolonged, high-speeds over a wash-boarded surface), which resulted in a very high frequency dynamically-varying load, a similar failure occurred - the rollers destroyed the surface of the shaft, and the shaft would then break at that point due to the induced stress concentration.
If my memory is accurate, at this point in the development process, we were using a 1040 or 1045 plain carbon steel due to cost (it was a production vehicle). I don't recall the heat treatment used to get the surface hardness needed, but it obviously wasn't exotic. When we ran into this problem, cost was the major design constraint, so going to an alloy steel with an exotic heat treat spec wasn't really an option. We tried many solutions, most of which solved the problem but were too costly. In the end, we simply added salt-bath nitriding to the part, and that gave us the bump in surface hardness to prevent this failure. Was it the best solution to this problem? Hell if I know - once we solved the problem within our design window, we stopped finding solutions because this was just one of many problems to solve and had to move on. If someone were to come to me with a better solution and berate me for not finding it, I'd probably have pointed out that there's more than one way to skin a rabbit, but all result in a skinned rabbit.
That’s like saying you can’t have a nice crispy burger on the outside without it being too dry on the inside (when the cooking process is the actual problem).
There can be a great balance between hardness and toughness of chromoly if you properly dial in your heat treat recipe.
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It’s not hard to figure out the recipe…and doing so can provide superior through hardness (for applications when it matters).Suffering from insomnia again this evening (morning?)...
What I meant by it being a compromise to use the shaft as a bearing race is that it trades something (cost, packaging, assembly weight, all of the above?) for part complication (adding another mechanical property - surface hardness - into the equation).
And with u-joints, a similar compromise is made, but it's a different part, with different design parameters, so there may be a different solution that works better for that different part. We engineers make design decisions for many reasons, and we don't all think alike, so our design solutions, even for the exact same part, may be different, but if they work, they work, right?
Many years ago, when working for a US-based powersports company, we had a similar design situation for a much smaller axle (about 8" long and 0,750" in diameter) with much smaller torques in a new design under development. Under one particular real-world load case (think prolonged, high-speeds over a wash-boarded surface), which resulted in a very high frequency dynamically-varying load, a similar failure occurred - the rollers destroyed the surface of the shaft, and the shaft would then break at that point due to the induced stress concentration.
If my memory is accurate, at this point in the development process, we were using a 1040 or 1045 plain carbon steel due to cost (it was a production vehicle). I don't recall the heat treatment used to get the surface hardness needed, but it obviously wasn't exotic. When we ran into this problem, cost was the major design constraint, so going to an alloy steel with an exotic heat treat spec wasn't really an option. We tried many solutions, most of which solved the problem but were too costly. In the end, we simply added salt-bath nitriding to the part, and that gave us the bump in surface hardness to prevent this failure. Was it the best solution to this problem? Hell if I know - once we solved the problem within our design window, we stopped finding solutions because this was just one of many problems to solve and had to move on. If someone were to come to me with a better solution and berate me for not finding it, I'd probably have pointed out that there's more than one way to skin a rabbit, but all result in a skinned rabbit.
OP
You are correct. I have engineering textbooks on steel selection, including sections on heat treatment, for that very reason. But that recipe could push the part out of the design envelope (too expensive, for example). Heat treatment undoubtedly adds an element of cost and manufacturing complexity. The simpler heat treatment recipe that works is generally the one that's selected.
But we've once again veered from the intent of my comment about a compromise. My argument is not that it's impossible to use a chromoly series steel for the Dana 35 axles. It's just not easy, and that's why it's not the prevalent steel used.
OP
There are two reasons to kill and skin a rabbit. One is to eat it, and the other is to put up the fur. In either case, expedience of method trumps elegance of method. Sometimes elegance and expedience meet, but if they don't, elegance will more often then not fall out. Same with manufacturing methods.
That may have changed in recent years, but that was the problem since forever. Axle companies fell victim to their perceptions that customers recognized 4340 and similar 4xxx alloys as be super strength and the superior answer because it was used in press on bearing applications with very high success. The vast majority of them copied that without doing any research into why it was not a good choice. The tail was wagging the dog on that one. We as customers also suck due to our ignorance about stuff like that. If you throw down two axles made by someone who knows what they are doing one being 4340 and the other 4140, the average customer will buy the 4340 first. I'll take the 4140 because it makes a better semi-float axle.
Customer ignorance is great for some companies though. They use the gotcha buzz words like chromoly to suck folks in while fully understanding that all it does is add unnecessary expense if you aren't going to heat treat it to bring about some of its desirable properties.