Twice this past weekend I sheared the roll-pin that holds the u-joint yoke to the front differential drive shaft (the rear yoke - closest to the pillow-block bearing). I'm a little confused about the cause as there is some room for intended slippage on the shaft and nothing looks out of kilter. I was blading some extremely rugged terrain at the time. Any ideas?
Sheared Roll-Pin BX-22
- Thread starter Rocketman
- Start date
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GFB
Member
I recently sheared the pin on the front yoke. NO good reason why that I know of. Someone else indicated the same thing had happened to their BX. I had been using my BX in rough terrain too but don't understand the correlation there might be, if any.
Gerry
Gerry
Pks
Platinum Member
- Joined
- Apr 6, 2000
- Messages
- 773
- Location
- Saline, Michigan
- Tractor
- Kubota L3700SU, Cub Cadet 1430, Hustler Super-Z 66in, Vermeer 1250
It has been my experience, IMHO, from both usage and design: roll pins are not supposed to shear. Bolts are for shearing. Pins keep things pinned together.
Is the pin able to rattle in its hole? That would cause a sheared pin.
If the pin is shearing, I suspect it's the pin's fault (brittle from bad manufacture process) or its diameter is too small (incorrect design).
Can you view the break under a magnifying lens? If you see a flat break, then the pin was probably brittle.
However, it is possible your driveline is having problems. After the pin has broken, can you spin the front wheels by hand? If not, then friction somewhere in the axle assembly may be the cause.
If you can get a new pin from your dealer and perform the same loading without failure, then you'll have your answer.
To give you an idea as to how strong that pin should be; I have been able to stall my B2400 running at 2000 RPM while digging in sand in 4x4 mode with R1 tires. The tires kept digging into the sand until they were burried; that's when the motor ran out of juice.
Is the pin able to rattle in its hole? That would cause a sheared pin.
If the pin is shearing, I suspect it's the pin's fault (brittle from bad manufacture process) or its diameter is too small (incorrect design).
Can you view the break under a magnifying lens? If you see a flat break, then the pin was probably brittle.
However, it is possible your driveline is having problems. After the pin has broken, can you spin the front wheels by hand? If not, then friction somewhere in the axle assembly may be the cause.
If you can get a new pin from your dealer and perform the same loading without failure, then you'll have your answer.
To give you an idea as to how strong that pin should be; I have been able to stall my B2400 running at 2000 RPM while digging in sand in 4x4 mode with R1 tires. The tires kept digging into the sand until they were burried; that's when the motor ran out of juice.
jrlichina
Platinum Member
Roll pins are used all the time as "shear pins" not just to keep stuff together. It's actually doing what it's designed to do, shearing under too much load. If you think something is actually wrong you would have to look at your front axle drive components. It's possible that something in the differential or axle bevel gears are binding. You may also want to check to see how tight the splines fit into the yokes. If they are too loose that would cause excessive movement which could cause the pin to fail. Also check the opposite end of the propeller shaft it is a slip joint. If this is binding(not extending) it will pull on the shaft shearing the pin in the front yoke. This is the most likely cause of the pin shearing.
Pks
Platinum Member
- Joined
- Apr 6, 2000
- Messages
- 773
- Location
- Saline, Michigan
- Tractor
- Kubota L3700SU, Cub Cadet 1430, Hustler Super-Z 66in, Vermeer 1250
jrlichina
Really? You're sure? Hmmm...learn sumthin' new every day!
When I was part of the conveyor industry, the industry standards we followed didn't allow roll pins to have that function. We HAD to use bolts, of the proper grade, that were grooved to a specific depth (depending on the maximum load).
And the Big 3 car companies wouldn't let us design with roll pins, as shear pins, either.
I wonder if things have changed a bit, or if our standards were just industry specific?
Thanks for the update.
Really? You're sure? Hmmm...learn sumthin' new every day!
When I was part of the conveyor industry, the industry standards we followed didn't allow roll pins to have that function. We HAD to use bolts, of the proper grade, that were grooved to a specific depth (depending on the maximum load).
And the Big 3 car companies wouldn't let us design with roll pins, as shear pins, either.
I wonder if things have changed a bit, or if our standards were just industry specific?
Thanks for the update.
jrlichina
Platinum Member
Yes it most certainly industry specific just as you indicated. I spent many years in plant automation and roll pins would never fly because of working loads and safety factors. In lower power powertrain components the loads are significantly less and the strength of the components follow proportionaly. Using say a grade 2 shear bolt could strip the teeth clean off the gears in the transaxle or the front pinion gears, etc. Roll pins are used for smaller rototiller tine hubs to driveshaft and simular lighter duty equipment. Like I said I think it is most likely the slip joint not slipping. Which then yanks the shaft out of the yoke. He could have just gotten a bad batch of pins or mistakenly used aluminum pins instead of steel pins. Who knows until he checks out a few things.
After a little investigation, it seems the rollpins were backing out and allowing the slip joint to, well, slip. As the roll pin was left holding on by only an edge, it would break the pin and gave the appearance of shearing off.
Well, I picked up some "high-end" roll pins from the fabrication shop at work and installed them on the yoke. After about an hour of work, I checked them and observed both pins were starting to back out a little. I put the tractor on a lift and ran the drive train to check for unusual vibrations, etc, - I saw none. So, I got out the MIG and put a small tack at the junction of the yoke and roll pin. During 5 hours of very hard use, I noticed no additional problems.........The down side is that when I have to take it apart again, I'll need to get the angle grinder out.
I'm still unsure of what was causing the pins to back out /forums/images/graemlins/confused.gif. The replacements I used were the same diameter as the ones that came on the tractor originally and were good and snug during installation. I guess time will tell if there is a different problem lurking.
Well, I picked up some "high-end" roll pins from the fabrication shop at work and installed them on the yoke. After about an hour of work, I checked them and observed both pins were starting to back out a little. I put the tractor on a lift and ran the drive train to check for unusual vibrations, etc, - I saw none. So, I got out the MIG and put a small tack at the junction of the yoke and roll pin. During 5 hours of very hard use, I noticed no additional problems.........The down side is that when I have to take it apart again, I'll need to get the angle grinder out.
I'm still unsure of what was causing the pins to back out /forums/images/graemlins/confused.gif. The replacements I used were the same diameter as the ones that came on the tractor originally and were good and snug during installation. I guess time will tell if there is a different problem lurking.
art
Super Member
We have had some occurance of the problem you described with the pins backing out, tape, wire and prick punches have seemed to have cure the problem on the units that have been brought to our attention.
JerryG
Super Member
Is there enough room to safety wire the roll pin?
