Snow Blower Drive - Roll Pin Question

[aczlan]

^^^correct...the OP should remove the shear pins and make sure the slip pieces are not rusted solid.

Excellent point, a roll pin is a whole lot cheaper than the gearbox.
Just to confirm, we are discussing part number 2 in the diagram below correct?


Aaron Z

 

[Citydude]

It's truly amazing the small tid bits of knowledge that TBN provides.

I would have never thought of using a drill bit to measure the size of a machined hole. So simple but sometimes evasive to a shade tree mechanic as myself.

Thanks Dale!

Roll Pins are by nature interference fit, they need to be drive in and should never "fall out' if it falls out it is wrong size (too small) .... As some famous carpenter says "measure twice cut once"...

IF I don't know size of hole, I use a drill bit as size gauge and go from there...

Dale

 

[LouNY]

Roll Pins are by nature interference fit, they need to be drive in and should never "fall out' if it falls out it is wrong size (too small) .... As some famous carpenter says "measure twice cut once"...

IF I don't know size of hole, I use a drill bit as size gauge and go from there...

Dale

They may not fall out, but under cyclic loads they will tend to fail and then start to move,
once part way out they will shear.

 

[WranglerX]

It's truly amazing the small tid bits of knowledge that TBN provides.

I would have never thought of using a drill bit to measure the size of a machined hole. So simple but sometimes evasive to a shade tree mechanic as myself.

Thanks Dale!

Ever thought of using open end wrench as a thickness (bolt shank) measuring tool?

Dale

 

[Citydude]

Never would have thought of that. Thanks!

Ever thought of using open end wrench as a thickness (bolt shank) measuring tool?

Dale

 

[SPYDERLK]

Hi,

experienced back yard mechanic but a novice when it comes to roll pins, so I could use some thought from someone who is.

I have a NH TZ25DA tractor with a NH 50CS front mount snow blower attachment. For the second time I have somehow damaged/lost a roll pin in the drive path. Starting from the auger back toward the mid PTO drive, here is what I have:

The two augers are on horizontal shafts that are driven my a gearbox. The augers are attached with shear bolts. From the gearbox, another shaft runs back toward the tractor, and the secondary thrower (fan) is attached to this shaft with a shear bolt. This shaft drives a gear on the back side of the blower, which is connected to another gear/driveshaft** with a chain. This driveshaft connects to the quickhitch to be driven by the mid pto driveshaft. So it goes driveshaft from blower->gear->chain->gear**->driveshaft**->quickhitch (to POT driveshaft)

The gear/driveshaft** is a part that is offered by NH as only an assembly (H40C12). However, the gear is/was connected to the shaft with a roll pin. The first time it broke it looks like the pin sheared. I found a roll pin that seemed to fit, but my dim memort tells me it might have fit looser than I wanted (SAE vs metric?). Since they are not separate parts there is no spec on the roll pin size. The second time (a couple years later and a couple days ago) when the snow stopped blowing, I took a look and the pin is gone.

I am almost 100% positive this pin was never meant to shear, as there are shear bolts on the augers and the fan. Right? I also am betting I put a pin in that eventually worked itself out. I imagine since these tractors were built overseas, the roll pin must be metric, right? Also, are their different hardness/ratings on these pins?

I spoke with one of the local NH dealers and they couldn't offer any help, they would only replace the assembly (must not be farmers). Not only do I not want to replace the assembly, the pin hole is accessible to repair without disassembly

Any thought?
Thank you, Jim

Once you are sure that all shear bolts are active replace that roll pin with a spiral pin.
McMaster-Carr

Also, regarding use of drill bit to gauge the hole size, note that close distinctions are needed to gauge between close and right . For this, a 2 flute spiral is not as good as a fully round section gauge pin. Use of a drill bit round shank can fool you too because it is actually very slightly smaller than the drill size, but if mechanically embossed with the bit size can act bigger as a hole gauge.​

 

[Dutch445]

it looks like that blower is made under a few different brands, kubota, or NH etc,
and it looks like part #2 as Aczlan asked about is available standalone, and the same
whether it's in NH or Kubota, i'm assuming the blower head is made by BerVac for
many
quick look and this pops up, a thread with part numbers and pictures right here on TBN
https://www.tractorbynet.com/forums/kubota-owning-operating/135281-b2789-snowblower-shear-bolts.html

 

[Redrum]

to all that contributed, thank you. Sorry for the late reply. I wasn't getting email notifications of new posts, but that was my fault. I really do appreciate the insight.

Anyhow, aczian, yes, #2. I ended up just taking the snowblower drive apart to get the part accessible on a bench, rather than try to fix in place. The roll pin indeed did shear. I took the assembly down to the local law mower shop and identified it was a 1/4" x 1 1/4" roll pin. I bought two. Total bill $2. It's funny because the tractor is made overseas so it's metric, but I keep forgetting that the attachments could come from a different place, and indeed are SAE.

The blower has 3 shear bolts, one on each auger, and one on the "fan" (secondary stage). I have sheared auger bolts before, so I am sure it's from the fan. Because of the gear ratio, I would think that the torque seen at the gear/pin would be much less than at the fan shear bolt. I think I'll replace that shear bolt "just because". It's alot easier fix if that shears.

Anyhow, cheers, and happy holidays!
Jim

 

[Redrum]

^^^correct...the OP should remove the shear pins and make sure the slip pieces are not rusted solid.

yes, I forgot to mention I will do that when I replace the shear bolt for the fan. Thank you.