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Snapped drawbar - anyone ever seen this before?

Posted: Sun Nov 25, 2018 7:18 pm
by bedwards1966
Has anyone ever seen this happen before? Clean break, the drawbar was on its shortest setting. Nobody was hurt, and nothing else suffered serious damage.
I'm curious as to what grade/type the metal is, if anyone knows this?
DB drawbar 1 small.jpg
DB drawbar 1 small.jpg (247.35 KiB) Viewed 1957 times
DB drawbar 2 small.jpg
DB drawbar 2 small.jpg (240.8 KiB) Viewed 1957 times
DB drawbar 3 small.jpg
DB drawbar 3 small.jpg (230.65 KiB) Viewed 1957 times
DB drawbar 4 small.jpg
DB drawbar 4 small.jpg (219.64 KiB) Viewed 1957 times

Re: Snapped drawbar - anyone ever seen this before?

Posted: Sun Nov 25, 2018 7:44 pm
by db2d
The answer is obvious. - it has been welded.

Re: Snapped drawbar - anyone ever seen this before?

Posted: Sun Nov 25, 2018 8:00 pm
by GeoffDEAL
The position of the welding has caused a stress point causing the break the top piece has no reason to be welded to the lower, the steel would be a high tensile almost spring steel and should not be welded on. The early 30 and 25 tractors had welded drawbars but construction was different and probably the steel and not subject to the loads on later drawbars.

Re: Snapped drawbar - anyone ever seen this before?

Posted: Sun Nov 25, 2018 9:04 pm
by bedwards1966
Indeed it has been welded, and the weld has gone to the corner of the metal which is a bad thing. However, the weld doesn't go across the piece which certainly does cause cracks, I'm surprised to see such a sudden failure from this.
Given how many drawbars are out there welded together (usually done far worse than this) which don't seem to break I'm surprised to see this has happened, first time I've ever seen it happen.

Re: Snapped drawbar - anyone ever seen this before?

Posted: Mon Nov 26, 2018 1:42 am
by Gard
It looks to me like a classic fatigue failure of steel to me. Typically a crack starts at a small defect at the surface, with each loading and unloading cycle the crack grows a small amount until it goes almost all the way thru the part. A machine shop can determine the hardness or strength of steel with a hardness test. This is the same look of broken springs or crankshafts. Welding of high strength steel without using the correct rods and heat treatment can cause cracks to start, they can also start at sharp corners or corrosion pits. Very cool pictures, thanks for sharing. There looks to be some corrosion near the edge so the crack may of been growing unnoticed for some time.

Re: Snapped drawbar - anyone ever seen this before?

Posted: Mon Nov 26, 2018 3:21 am
by cobbadog
Sorry you had this fail but I also feel it was due to the welding. If it was meant to be welded I'm sure D.B. would have done it for us. there is a lot to be said about running welds in certain places and people with the correct skills and training can do it when it is required but that was not required. The other side of it all is what kind of life has it had over time?

Re: Snapped drawbar - anyone ever seen this before?

Posted: Mon Nov 26, 2018 10:18 am
by SteveCollett
Classic stress failure started at the welding but mainly through overloading the drawbar.
The strange thing is it did not go through the bolt holes

Re: Snapped drawbar - anyone ever seen this before?

Posted: Mon Nov 26, 2018 10:53 am
by skyrydr2
For sure failed due to weld. Looks to me like the hitch point could not flex enough due to a heavy load and the tractor started up a steep incline? Those draw bars are not made of some fancy exotic steel, they can be drilled and welded and threaded.
You want a good steel though, T1 or X1050 or maybe even D2 but they all need to be sure the grain structure is going the correct way or it will fail again.
Never weld the top tang on ! Its bolted on for just this reason.
If you had bent or partially sheared the pin you would have a doosy of a time getting it out with the tang welded on..

Re: Snapped drawbar - anyone ever seen this before?

Posted: Mon Nov 26, 2018 8:03 pm
by Ian
Yes I have seen a few snaped in the past but many years ago on a 770 and 780

Re: Snapped drawbar - anyone ever seen this before?

Posted: Fri Nov 30, 2018 9:22 am
by SteveCollett
I would guess it had been attached to something with a double clevis, this can impose huge loads on the drawbar

Re: Snapped drawbar - anyone ever seen this before?

Posted: Fri Nov 30, 2018 12:23 pm
by Scooby
And maybe usd in it's fully extended position and then instead of using it like a clevis drawbar used it like a pickup hook and picked up something too heavy ?

Re: Snapped drawbar - anyone ever seen this before?

Posted: Sat Dec 01, 2018 9:48 am
by SteveCollett
you say that Scooby, but I think we used the clevis to pick up far more than the proper hook because the risk of losing trailers . I have never snapped a DB drawbar but have JD and Ford.
We certtainly gave these poor tractors some stick, why I have so much admiration for them

Re: Snapped drawbar - anyone ever seen this before?

Posted: Sat Dec 01, 2018 10:34 am
by Scooby
I just wondered if it might have been the cause Steve. But I do agree with you that they would stand a lot of abuse. I was once asked to go and load a BTD6 Drott used for muck loading onto it's usual two wheeled trailer where most of the weight was on the drawbar and take it back to a contractor friend's yard. I was using his DB 1200 to do it and I just backed up to the drawbar of the trailer and picked it up, not even considering that the tractor drawbar was extended right out which it had been because it had been on a Kidd muckspreader. Then I drove up a very steep hill !! :oops: I reckon the Drott would have been about 7 tons and I would certainly have had 5 tns on the drawbar of the tractor.

That would have been 40+ years ago and I still worry about what would have happened if the pin or the drawbar had snapped. I was on a busy road all the way back. :oops: :oops: Something was looking after me that day.

Re: Snapped drawbar - anyone ever seen this before?

Posted: Sat Dec 01, 2018 12:22 pm
by bedwards1966
More information...

The drawbar was on its shortest setting.

It was being used with a normal, single eye on the trailer (not a double clevis or anything daft like that).

The trailer was nose heavy but the tractor did lift and latch it and tow it about 30 miles before this happened.
It was driving on a flat road at the time this happened.

The photo does make it appear that a crack may have started but it's actually dirt, it took a couple of days to get time to take a photo. I looked at it closely when it was fresh and it did all appear to have happened in one go.

Had it been an excessive amount of nose weight I would expect a tyre to give out long before a drawbar.

Re: Snapped drawbar - anyone ever seen this before?

Posted: Sat Dec 01, 2018 9:09 pm
by joeproctor
the fact that you run on the short setting would mean less springy and more ridgid plus the fact it had been welded!

i have just purchased a 1690t and the draw bar was snapped off, not been welded but i would guess it may have been abused!