Siromer/Jinma 254 - Improving the lift bar stabilisers

[aesmith]

The welded repair held up for the January snow, but broke on my first session in March. It actually wasn't the welded repair itself that broke, the pin broke the other side of the bar. I guess a weakness in the reduction from 19 to 16mm.

I decided to go with a 16mm bolt and sleeve rather than drilling out the arm, I don't have a 19mm drill bit to hand for a start. We'll see how this holds up although hopefully I won't need the snowblower until next Winter. Once it's had some use I'll whip it off and look for any signs of the bolt bending, if so then plan B will be a 19mm rig like you show.

 

[piper184]

That bolt and spacer will probably be stronger than the original pin. Those pins are not made from the best steel, and I am betting that when they turned down the shank for the threads they did not properly radius the inside shoulder. This would leave a stress riser right at the point of most stress.

In any case, the bottom of the threads make the working diameter even smaller which is why I think the threaded portion should be larger than the pin portion.

The CAT 1 pins I have seen as standard off the shelf items never have the threaded shank be a smaller diameter than the pin. I don't remember for sure, but I think these link pins are not standard CAT1 size and that is why I went with the bolt instead of ordering more inferior OEM pins.

Your solution should work fine especially if you can get some grade 5 or 8 bolts so they are a little harder. Oops, I guess that would be something like a 10.8 or 12.8 in metric as opposed to the hardware store grade of 8.8.

The real key to getting good strength is to make sure you can apply full clamping force (torque) at the nut. As long as the sleeve can take "the squeeze" it will be just fine.

 

[aesmith]

I don't remember for sure, but I think these link pins are not standard CAT1 size.

That's correct, Cat 1 lower pins are bigger at 22mm (or maybe strictly 7/8").

I think my bolts will be strong enough, but it's only the snowblower that will really test it. The advantage is they're off the shelf parts so can be replaced quickly and easily. Make them stronger and maybe something else will break.
My bolts are 8.8 which I thought equivalent to Grade 5 rather than 2, I guess I could look that up. It would be easy enough to find 10.9.

 

[Bob Rooks]

This casual observer thinks the pin was not threaded up tight, which led to it's failure. It appears the the threaded portion next to the shoulder looks "stretched" and hammered. The threads look like the rolled type, which are actually stronger than the cut type, and are not used on poor quality material due to expense. All that leads me to believe the pin was loose, putting the load fulcrum on the threaded portion of the pin next to the shoulder instead of being distributed around the shoulder.
Just my 2¢.
PS: I couldn't detect a radius in a close up, but that's not saying there wasn't one.

 

[piper184]

In the case of my tractor, the thread on the pin to the thread in the nut fit was so poor that it was impossible to hold them tight. I tried extra washers to get the nut out to fresh threads and even thread locker but nothing could keep them tight. Once they loosened up, it was short order for them to fail. Mine didn't break, but I got tired of the slopping around and replaced them with the bolts drilling the holes to a larger diameter meant greater torque could be applied. Never came loose since.

I'll have to look and see if I saved the old pin in the scrap bin. If so I can check it for a radius. I see a lot of low quality import stuff that does not have "proper" machining techniques applied.

I didn't pay for a high end product and have no problem making improvements when needed. Who knows, in another 15 years it may not even say Jinma on the side anymore! It gets the jobs done and for the $ invested, I am still ahead of the game. Besides, I like fixing things, so it is cheap entertainment.

 

[aesmith]

Cheers. I suspect you're correct either loose at the time, or weakened from being loose in the past.

 

[Tinhack]

I put the chains and turnbuckles back on my Ford. I got a pair of the sliding tube design, but they were either loose or too tight. The tube holes were never in the right place. The turnbuckles allow for precise adjustments. One thing, for sure, is that the forward mounts MUST be on the same plain as the lower lift bars.

Ford had a better idea. The forward chain mounts are part of the ROPS mounting brackets. There're dropdowns on the lower ROPS brackets that put the pivot point in alignment with the lift bar pivot. The picture below shows the chain on the right side, but the dropdown bracket can be seen on the left side.