hi everyone ,

I am searching that picture of the crawler tractor that moved uphill when suddenly the complete chassis overturned backward . This was a terrible accident .
Normaly this can only happen when someone has "forgotten" to mount the so called shackles that hold together the main frame and the equaliser bar .
I know there is a picture of this accident . If someone could show it , that would be great . I only use it for educational purposes .
Thanks in advance . The Netherlands , Johan 7

This one 

Yikes! D4C? That's a new one for me, I will look up others that did not have the "Pony" springs attached, that flopped over. Hopefully the operator may have only suffered a bad headache on this one? A farmer from across the river here had the same on their D4C, but no cab to catch their operator; unfortunately, that poor fellow passed. Tractor is still parked inside as a bad reminder. JM

I remember a D4 and lite disc on the bank of a canal or irrigation revisor with a orchard in the picture too. All on this forum sometime since 09 when I started watching here. I believe the operator survived, which looked a miracle. It was an eye-opening monument for me.

I think this was the classic one....
 

I will be looking under 4 Cats tomorrow. I had never considered that as a hazard. Grant.

Hi, GrantJ.
Cat hasn't made much ovva habit of putting things on their products that don't serve some useful purpose.

Just my 0.02.

operating without the pony spring fitted , not only flip but can rise up and slam back down if you drop the clutch at high revs damaging the sump

Dumb question but what do these pony springs look like? Makes me want to check out my D2 to see how it is set up.

Hi, rhartwick.
The pony spring or retainer spring is located under the equaliser spring but not attached to it. Instead, it is attached to the underside of the engine by pairs of hangers to stop the tractor rearing up off the equaliser spring and flipping over backwards as shown on the images above.

Without this restraint, the tractor can wind itself over its final drive gears very quickly with the results that you can see in those images. Tractors with dozer blades hung off the nose are less likely to do it but could still exhibit that tendency up to a point where the geometry of the dozer in relation to the track frames and the tractor might stop it.

Just my 0.02.