Don't know how this happened

[bindian]

While changing transmission fluid today, for the first time. I notice a bolt missing on the right tractor subframe for my backhoe. I had the backhoe already off to mount the 3PH arms and the brushog. When I got a mirror to look up in the hole, I saw that the bolt was sheared. It looked like it had enough meat left to remove it with vise grips after getting the subframe loose and moved over. I loosened and removed all bolts, but the two forward bolts. I lowered the subframe (one inch thick and HEAVY) with a bottle jack in back while the two loose forward bolts kept it from falling off the jack. I had to heat the bolt (all threads were saturated in locktite paste on installation 2 & 1/2 years ago) to break the locktite bond. After a little heat, I tightened a pipe wrench on it and slowly removed it. This all after I had the tire off and the tractor blocked up in 3 places. I put it all back together while measuring the spacing for the left and right subframe halves to get them spaced right. Each time in the past, I had to pry one subframe half to get it to pop in the clevis when mounting the backhoe. Now it should drop right in place.
hugs, Brandi

 

[Owenslee]

What grade designation are on the heads of the attachment bolts?

Doesn't look like a fun job but you were fortunate a portion of the broken bolt was still accessible.

Kerry

 

[bindian]

What grade designation are on the heads of the attachment bolts?

Doesn't look like a fun job but you were fortunate a portion of the broken bolt was still accessible.

Kerry

Kerry,
I kept reading my parts manual and backhoe installation instructions, to see if they called out the bolt. It might be metric, as the front loader and brush guard bolts are, as I needed to buy a tap to clean them up, after modifying my brush guard. I finally found a statement in the instructions that the bolts were existing bolts. I didn't look at the head after that. I took one out after tightening all bolts and left it in the truck for my next trip to town. I will buy a case hardened bolt then. The bolt that sheared has to be started and tightened first as it goes beside the 65 or 70 degree mt. flange for the telescopic link. The left side's bolt is half way out and jammed into the mt. flange. I will have to buy a 15/16th crows foot to tighten it up as my crows feet at the hangar only go up to 7/8. The right one I reinstalled last night has enough room to get a 1/2 inch drive socket on it, but not a 3/4 drive, because of the side to side slot for adjustment. So I took a chance with my 1/2 inch breaker bar and the 4 foot cheater pipe on breaking it, but it only flexed real good. Yes, I was blessed in having meat to grip. Otherwise I would have had to drill and hope not to break an extractor in removing it.
hugs, Brandi

 

[bindian]

What grade designation are on the heads of the attachment bolts?

Doesn't look like a fun job but you were fortunate a portion of the broken bolt was still accessible.

Kerry

Kerry,
On the bolt head...........LPS. Also it says 10 9 with the numbers underlined and the 9 seems to be a little smaller. Sounds to me that it is metric. Won't know until tomorrow night when I get to the hangar, where all my taps and dies are.
hugs, Brandi

 

[Owenslee]

Yes the 10.9 is a medium carbon steel bolt that has been quenched and tempered and is approximately equal to a SAE grade 8 bolt.

It has minimum yield strength of 940 MPa ( mega pascals) or approximately 136,000 psi.

It also has a minimum tensile strength of 1040 MPa or about 150,000 PSI.

These specs are almost identical to a SAE grade 8.

A stronger alternative would be a 12.9 metric bolt with 160,000 psi min yield and 177,000 psi min tensile strength.

The problem is that you lose ductility as the strength and hardness increase. If heavily overloaded it is more likely to shear rather than stretch or bend. It also may also transfer more load to the threads increasing the chance of stripping the threads or cracking the casting.

The fact that the original 10.9 bolt sheared indicates a harder bolt may not be the solution.

Bolt strength selection is a balancing act... but I'm sure the Mahindra engineers made the selection based on good engineering practice and sound judgment.

I would stick to a 10.9 bolt from a known quality supplier.

Kerry

 

[tommu56]

Brandi
at work we get a lot of the odd metric stuff and bspt here
Metric Multistandard Components Corp.

and here is their chart on the thread types an d descriptions


http://www.metricmcc.com/catalog/Ch10/10-1005.pdf

tom

 

[Cacinok]

brandi, this is a good reminder why we should take the time to examine our heavy equipment looking for loose, missing, broken bolts and cracks. i try to do this when i wash my tractor, but still always manage to lose a bolt when i'm the farthest from the house i can get.

 

[bindian]

brandi, this is a good reminder why we should take the time to examine our heavy equipment looking for loose, missing, broken bolts and cracks. i try to do this when i wash my tractor, but still always manage to lose a bolt when i'm the farthest from the house i can get.

I do check the Big RED Beast over at each "bath" and greasing. Don't know if I just overlooked it or it happened since the last bath. I know anything is possilbe with max rpms for running the backhoe for best hydraulics.
hugs, Brandi

 

[Cacinok]

I do check the Big RED Beast over at each "bath" and greasing. Don't know if I just overlooked it or it happened since the last bath. I know anything is possilbe with max rpms for running the backhoe for best hydraulics.
hugs, Brandi

i didn't mean to imply that you didn't check/maintain things, i was making a general statement. same thing happens to me, i check things over, but still manage to lose or break a bolt out in the sticks. the loader is the worst offender.

 

[brin]

I had to stop bush hogging early today after only 5 hrs. because the bolt to the bracket from one of the lift arms to the bracket that attaches to the deck decided to fall out...fortunately I heard the noise and stopped before any damage was done..I will replace it first thing in the AM and get back to work..had I been wearing head phones and listening to the radio there would have been damage or worse the bush hog could have crawled up the back tire and joined me on the drivers seat...not good...I had just service the BH befoe going out..all bolts were checked so this must have snapped.?? It happens even when you check things out...that is machinery..