hey can either of you guys shoot me a private measage - trying to see how things are going with the d-44 joints ? anyone heard?

[ 09-23-2001: Message edited by: onetoncv ]

Originally posted by onetoncv:
<STRONG>hey can either of you guys shoot me a private measage - trying to see how things are going with the d-44 joints ? anyone heard?

[ 09-23-2001: Message edited by: onetoncv ]

</STRONG>

well i think it may need some more development. <IMG SRC="smilies/biggrin.gif" border="0"> kelly broke it on stage 7. she was "getting it" on a very hard section and broke the cross.

did she break anything else or just the joint - are you shure it was the joint we were tring out camo? he only had one - go any pics? thanks for the news- Jess

[ 09-23-2001: Message edited by: onetoncv ]

was it in johns rig? i thought we were going to try our new joint in lances cruzer? did you have time to change an axle and install it on johns toy? thanks for the info- Jess

Originally posted by onetoncv:
<STRONG>are you shure it was the joint we were tring out camo? </STRONG>

<IMG width=640 height=480 SRC="http://www.pirate4x4.com/ubb/uploads/pretty_sure.jpg">

Pretty sure. <IMG SRC="smilies/thefinger.gif" border="0">

Well, it was a nice clean break ... <IMG SRC="smilies/rolleyes.gif" border="0">

there's it is- broke as hell- thanks camo for the pic's - those joints suck- time for round 2 -Jess

Originally posted by onetoncv:
<STRONG>was it in johns rig? i thought we were going to try our new joint in lances cruzer? did you have time to change an axle and install it on johns toy? thanks for the info- Jess</STRONG>

yes it was in kellys rig. the all-pro truck has a hybred 60 in it.

what material was that made out of?

Originally posted by onetoncv:
<STRONG>there's it is- broke as hell- thanks camo for the pic's - those joints suck- time for round 2 -Jess</STRONG>

LOL indeed. <IMG SRC="smilies/biggrin.gif" border="0">

4340 moly- not the (shit) as far as i can see- did anything else break camo? back to the drawing board- glad i did not sink 1,000s of dollars until i knew for sure-

ripped the ears off the inner axle because they had to drive the rest of stage 7 to get off the course.

maybe try 300m on your next one.

Sorry to see the break but from a guy just out to build a trail rig it sure is nice to see a developer checking on his/her own product!!!!
<IMG SRC="smilies/usa.gif" border="0"> <IMG SRC="smilies/beer.gif" border="0"> <IMG SRC="smilies/usa.gif" border="0">

That sucks they was such a pretty u-joint. Well back to the drawing board. Will try to think of something else to use in there. After you take a look at it Jesse would you please send it to me so I can look at it. How much abuse did it take before it broke? Was it better than the Spicer Joint?

my exact sediments donovan - hope to get it back to see and maybe metal test it- hope lance does not throw it at me- Jess

Yes that could really hurt. <IMG SRC="smilies/biggrin.gif" border="0">

Hmmm... possibly a victim of stress concentration? Looks like there was a sharp transition between the bearing surface and the cross. The affect of that transition radius on the local stress is called the "Stress Concentration Factor" and it can be dramatic. Just thinkin' the material selection might be fine and it's the design that's gettin' ya.

I was thinking the same thing loooking at it. Maybe you want to try something with a little less of a stress riser there. Can one be made that necks down to the bearing surface? or maybe round the interface a little bit. Might end up being quite a bit stronger.

Haven't looked at my enginerding books in a while, but seems to me that the sharp corners should be avoided in something like that.

=John

Originally posted by RoverOver:
<STRONG>enginerding</STRONG>

LOL <IMG SRC="smilies/thefinger.gif" border="0">

A brittle material is especially susceptible to stress concentration. Check out MP35N, that stuff kicks ass (still gotta reduce the stress concentration though).

BTW, here's a great place to get material properties: http://www.matweb.com

Offer a free d-shaft to one of the enginerds on here in exchange for some FEA analysis. If I wasn't so rusty at it I'd help ya <IMG SRC="smilies/frown.gif" border="0">

[ 09-23-2001: Message edited by: Eric Ruhl ]

MP is great except for machining and galling. Since he got rid of the needle bearings galling would be a problem. If it was a fatigue failure MP or another cobalt-chrome alloy would be the way to go, but from the picture it looks like it was not or at least the fast fracture region was very large. I think he mentioned it was heat treated to 280 KSI. In that case 4340 would be kinda brittle and the stress concentration factors others mentioned would be significant.

Well I will tell you guys the joints was heat treated to 50 Rc and I had .060 raduis in the corner of them. They was built just like a stock Neapco U-joint. I think that maybe we should put in a larger raduis in the corner like .120" or change material and put the larger raduis in there. We had to start somewhere.

Well that was a good place to start a bigger radius seems like a good place to go next. any of those alloys with a better fracture toughness are expensive and much more difficult to machine, so the cost of the new joint would price it out of the market. Donovan get that joint back and look at the fractue surface. I would be currious to see if there was a small quench crack at the initiation site. Do you know the material and hardness on the Neapco joint.

I know that a Spicer Joint is made out of 5120 material and they are around 60 Rc same with the Neapco.

http://www.pirate4x4.com/scrap/ujoint/joint1.jpg

http://www.pirate4x4.com/scrap/ujoint/joint2.jpg

Here are some more up close pics to analyze. Im no engineer, but it appears the failure had something to do with the part on the top of the upper picture.

[ 09-24-2001: Message edited by: Lance ]

might have been the grain in the material also- might think about forging them and breaking up or making the grain smaller and more compact- ? jess

arent spicer/nepco joints forged? I would think that would put them ahead in the strength issue. I am no engineer (actually working on that now <IMG SRC="smilies/biggrin.gif" border="0"> ) but I would think forged would be the only way to go on this

I think forging may be your solution, Jess.
It looks to me the the stress concentration got you. The radius was just to small. In the very last pic posted notice the uniform breakage at the top of the radius then the large chunk out of the back side. I think this may be the sign of the quench crack someone referred to earlier.

I totally argee that its great to see a company take such great pride in its products and such R&D to produce better products for us the consumers. Thanks Jess.

Yeah, forged would be the way to go, but you are looking at $5-10K for tooling, Any one want to put up some money? you would have to sell alot of joints to make get your investment back.
Does anyone know for a fact what material and the hardness of the one that broke? onetoncv? It's not like it's a trade secret or anything because it didn't work.

http://www.monsterslayer.com/jeep/Pics/joint2.jpg

rockwell 50 -

It appears that a larger radius could be used to decrease the stress riser at the break point. <IMG SRC="smilies/usa.gif" border="0">

http://www.pirate4x4.com/scrap/ujoint/joint2.jpg

Rockwell 50 for 4340 is about 230 KSI yield 250 ksi UTS and 10% elongation. Probably tempered at 600F exactly the heat treat I would recomend for this application if you were going to through harden it. Going forward to keep things reasonable cost wise you aren't going to want to change alloys, MP35N, Aermet 100, and 300M would be the next alloy choices, unfortunately with MP the material cost goes up by a factor of 10 and the machining time by a factor of 3. with the other choices only the material cost goes up significantly, and the strength doesn't go up a whole lot either these alloys just have better fracture toughness.

Really seems like you should stick with 4340 and look for a geometry that works, Like Donovan said get that radius up to .120 or even .250. And make sure there wasn't a quench crack in that part.

As far as grain size goes I bet that was an ASTM 7 or finer, assuming you started with hot rolled 4340. In that case going finer isn't really going to gain much. Same deal with the forging, with that high an alloy it isn't going to help a whole lot, maybe 10% stronger max.

Like everyone else said thats a good vendor.

Originally posted by Gordon:
<STRONG>Rockwell 50 for 4340 is about 230 KSI yield 250 ksi UTS and 10% elongation. Probably tempered at 600F exactly the heat treat I would recomend for this application if you were going to through harden it. Going forward to keep things reasonable cost wise you aren't going to want to change alloys, MP35N, Aermet 100, and 300M would be the next alloy choices, unfortunately with MP the material cost goes up by a factor of 10 and the machining time by a factor of 3. with the other choices only the material cost goes up significantly, and the strength doesn't go up a whole lot either these alloys just have better fracture toughness.

Really seems like you should stick with 4340 and look for a geometry that works, Like Donovan said get that radius up to .120 or even .250. And make sure there wasn't a quench crack in that part.

As far as grain size goes I bet that was an ASTM 7 or finer, assuming you started with hot rolled 4340. In that case going finer isn't really going to gain much. Same deal with the forging, with that high an alloy it isn't going to help a whole lot, maybe 10% stronger max.

Like everyone else said thats a good vendor.</STRONG>


Yeah what he said! <IMG SRC="smilies/eek.gif" border="0"> <IMG SRC="smilies/blush2.gif" border="0">

Jesse is a great vendor too! <IMG SRC="smilies/biggrin.gif" border="0">

Waspalloy, hastalloy, inconel series nickle alloys? I know that they are incredibly tough to machine, so your time goes up... <IMG SRC="smilies/question.gif" border="0">

I may be missing something, but why is only one nub breaking? Shouldn't both break at the same time (or would that be only if the wheel is straight), could it be that the ear are a bit loose? If it is the joint that is failing on its own would it help to have the body the same thickness as the maximum diameter of the nubs so there would be no stress concentration at the nub base, or have you already tried that? Whatever the solution, good luck.

milan

Originally posted by Gozuki:
<STRONG>Waspalloy, hastalloy, inconel series nickle alloys? I know that they are incredibly tough to machine, so your time goes up... <IMG SRC="smilies/question.gif" border="0"></STRONG>

Lot's O' luck Jeff on developing a better D44 U-joint.
I've finally going to get delivery (it is said) on the alloy front drive shafts that I put on order three months ago (every since I broke hard at "Dump & Hump" in Moab this spring ... witnessed by H8...
I'd really like to see a joint to acompany that investment in dependability.
Please do not construe any of my earlier posts to mean I am not behind you and your R & D efforts to develope a better mouse trap!
I am, and many more as you know are, eagerly awaiting a solution to the fraility of the standardly available U joints.
The best thing you can do (and have done) is to put your stuff to the test for public evaluation.
Cheers to you ... and keep it up ...


<IMG SRC="smilies/smile.gif" border="0">