I have a snowblower with the typical shear pins on each side of the front
augers. I usually use mild steel capscrews, but I've been having them
shear more often lately, in what seem to be only moderate loads. I need
to modify the size or material to make this more reliable. It's not fun
when one side shears 500 feet up my hill in Vermont at -15. Like
Yesterday. Grrr. And also Brrrr...

The unit has a .75 inch shaft running in a 1.0 inch OD tube with little
clearance. The shear pin holes are/were .25 inch, but they're a little
worn now.

I would like to find information on shear torque for this kind of
configuration: double contact shear at a certain radius, for different
materials. I want more torque than I have now, but not TOO much where I
may damage the drive worm-gearbox. I wish I knew:

- The present shear torque with mild steel 1/4"
- The shear torque with a grade 5 or grade 9 or other 1/4" bolt
- The shear torque with a 5/16" mild steel bolt etc.

I bet this is all in a table somewhere but the search I did didn't find
it...

Any suggestions or information would be appreciated!


--
Regards, Terry King ...In The Woods In Vermont

The one who Dies With The Most Parts LOSES!! What do you need?

I buy my pins at the true value hardware store. I have only once sheared a
pin, that I can thank my newspaper person for. It has been cold this week I
think 20% of my snow blowing today was spent warming my gloves 2" from the
muffler.

The unit has a .75 inch shaft running in a 1.0 inch OD tube with little
clearance. The shear pin holes are/were .25 inch, but they're a little
worn now.
I got a suggestion that this may be part of the problem.. the worn holes.
I'd drill them out to the next US size: 5/16" if I had SOME idea what the
resulting torque at shear might be..

Any ideas???

--
Regards, Terry King ...In The Woods In Vermont

The one who Dies With The Most Parts LOSES!! What do you need?

In article , Terry King says...

I have a snowblower with the typical shear pins on each side of the front
augers. I usually use mild steel capscrews, but I've been having them
shear more often lately, in what seem to be only moderate loads.

Have you actually *found* the sheared bolts? I thought I was
shearing them on my snowblower too, until I found one that
was intact on the ground - sans nut.

They were vibrating loose. The last ones I put in with locktite,
and they're still in place.

Jim

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==================================================

There is an assumption here, that just a little more torque allowed will
make a difference. If you're really picking up rocks and that is causing
the pins to go, I doubt a little more torque will make a difference.

Are you using locknuts or nylock nuts? I think Jim has a very good point
if not.

Terry King wrote:

- The shear torque with a grade 5 or grade 9


I *really* don't think you should do that!

Steve Smith

Buy snowblower shear bolts appropriate for your make/model machine. Any goot
H/W store or small engine service place should have them, or try:
http://www.jackssmallengines.com/snow_index.html

"Terry King" wrote in message
.. .
I have a snowblower with the typical shear pins on each side of the front
augers. I usually use mild steel capscrews, but I've been having them
shear more often lately, in what seem to be only moderate loads. I need
to modify the size or material to make this more reliable. It's not fun
when one side shears 500 feet up my hill in Vermont at -15. Like
Yesterday. Grrr. And also Brrrr...

The unit has a .75 inch shaft running in a 1.0 inch OD tube with little
clearance. The shear pin holes are/were .25 inch, but they're a little
worn now.

I would like to find information on shear torque for this kind of
configuration: double contact shear at a certain radius, for different
materials. I want more torque than I have now, but not TOO much where I
may damage the drive worm-gearbox. I wish I knew:

- The present shear torque with mild steel 1/4"
- The shear torque with a grade 5 or grade 9 or other 1/4" bolt
- The shear torque with a 5/16" mild steel bolt etc.

I bet this is all in a table somewhere but the search I did didn't find
it...

Any suggestions or information would be appreciated!


--
Regards, Terry King ...In The Woods In Vermont

The one who Dies With The Most Parts LOSES!! What do you need?

Buy snowblower shear bolts appropriate for your make/model machine. Any good
H/W store or small engine service place should have them,

I've used the hardware-store shear bolts; they actually shear a little
easier; they have small grooves in them.

They have definitely sheared; usually a central part is in the center
shaft and must be pushed out.

I HAVE jammed a couple of rocks; I WANT the pin to shear then! But I've
had the regular 1/4" bolts shear biting into a semi-frozen drift or
embankment.

Anyone have an idea what the ratio of shear torque would be for a 5/16"
mild steel bolt VS the 1/4" ones?? Is it proportional to area? Or some
other factor??

I'm realizing that the 'worn hole' thing may be significant; I think I
only sheared one the first season.. 5 years ago. I've moved a lot of
snow since then!!

--
Regards, Terry King ...In The Woods In Vermont

The one who Dies With The Most Parts LOSES!! What do you need?

Shear is directly proportional to the area. a 5/16" bolt would be
1.55 times more shear strength. Drilling it out to a clean hole
would also eliminate some unknown amount of bending that is going
on.

The grade 5 and grade 8 bolts would have more shear strength than
the usual soft steel but they would be much harder than the shaft
and tube so you would mangle them before the bolt sheared, NOT
what you want.

Terry King wrote:

Buy snowblower shear bolts appropriate for your make/model machine. Any good
H/W store or small engine service place should have them,


I've used the hardware-store shear bolts; they actually shear a little
easier; they have small grooves in them.

They have definitely sheared; usually a central part is in the center
shaft and must be pushed out.

I HAVE jammed a couple of rocks; I WANT the pin to shear then! But I've
had the regular 1/4" bolts shear biting into a semi-frozen drift or
embankment.

Anyone have an idea what the ratio of shear torque would be for a 5/16"
mild steel bolt VS the 1/4" ones?? Is it proportional to area? Or some
other factor??

I'm realizing that the 'worn hole' thing may be significant; I think I
only sheared one the first season.. 5 years ago. I've moved a lot of
snow since then!!

If the shear holes are getting battered, then perhaps it is the movement that
is contributing to the shear. Maybe new holes drilled ninety degrees out of
line of the old holes and some distance away?

I blow snow from 3 drives and the the ritual walk to remove the papers has
saved much aggravation.

John H.

Thanks for this:
Shear is directly proportional to the area. a 5/16" bolt would be
1.55 times more shear strength. Drilling it out to a clean hole
would also eliminate some unknown amount of bending that is going
on.

The grade 5 and grade 8 bolts would have more shear strength than
the usual soft steel but they would be much harder than the shaft
and tube so you would mangle them before the bolt sheared, NOT
what you want.
OK, Won't do that!

And, this comment:
If the shear holes are getting battered, then perhaps it is the
movement that is contributing to the shear. Maybe new holes drilled
ninety degrees out of line of the old holes and some distance away?

OK, here's what I think I'll do (Comments and GotYas appreciated):

1. Drill existing holes out to 5/16". Temporarily install 5/16 Capscews
(smooth shank). This should stabilize the current rotational 'slop'.

2. Drill new 1/4" holes in the stabilized tube and bar, an inch or so
away and 90 degrees to the original holes. Install 1/4" mild steel
capscrews.

3. Remove 5/16 capscrews, run for a while.

4. If problem continues a lot, use the 5/16" (1.5 times the shear torque)
mild steel capscrews.

I have 800 feet of dirt road to blow, and although I walk the path in the
Fall and throw a lot of stuff off, I always seem to miss the odd piece of
fallen branch, rock etc. So I understand that I'm in a difficult
environment.

Meanwhile, my Grandkids are coming this weekend, and we've got a dynamite
sliding hill with no traffic except the occasional snowmobile...

Thanks for the help in understanding this!

--
Regards, Terry King ...In The Woods In Vermont

The one who Dies With The Most Parts LOSES!! What do you need?

On Fri, 16 Jan 2004 09:11:16 -0500, Terry King
wrote:

Thanks for this:
Shear is directly proportional to the area. a 5/16" bolt would be
1.55 times more shear strength. Drilling it out to a clean hole
would also eliminate some unknown amount of bending that is going
on.

The grade 5 and grade 8 bolts would have more shear strength than
the usual soft steel but they would be much harder than the shaft
and tube so you would mangle them before the bolt sheared, NOT
what you want.
OK, Won't do that!


Generally a Grade 2 bolt is what you want for a shear pin, with a snug
fit. Which reminds me, I better pick up a couple sets for the old Noma
as I used the last set when I serviced it this fall.
And, this comment:
If the shear holes are getting battered, then perhaps it is the
movement that is contributing to the shear. Maybe new holes drilled
ninety degrees out of line of the old holes and some distance away?

OK, here's what I think I'll do (Comments and GotYas appreciated):

1. Drill existing holes out to 5/16". Temporarily install 5/16 Capscews
(smooth shank). This should stabilize the current rotational 'slop'.

2. Drill new 1/4" holes in the stabilized tube and bar, an inch or so
away and 90 degrees to the original holes. Install 1/4" mild steel
capscrews.

3. Remove 5/16 capscrews, run for a while.

4. If problem continues a lot, use the 5/16" (1.5 times the shear torque)
mild steel capscrews.

I have 800 feet of dirt road to blow, and although I walk the path in the
Fall and throw a lot of stuff off, I always seem to miss the odd piece of
fallen branch, rock etc. So I understand that I'm in a difficult
environment.

Meanwhile, my Grandkids are coming this weekend, and we've got a dynamite
sliding hill with no traffic except the occasional snowmobile...

Thanks for the help in understanding this!

If the pins are not fitting properly in the holes it won't take long for the
constant jerking of the auger to snap them. Is everything else on the
blower running nice and smooth? If not that could be part of your problem.

Years ago I had a 10HP Sears blower that ran good for a few years then it
started breaking the 3/4 inch hex drive shaft right where the chain
sprocket was welded on. After replacing 2 shaft and sprocket assemblies I
finally sold it and purchased a better quality Ariens snowblower.

Gravel driveways are much harder on blowers than paved driveways so I keep
mine set very high.

Jimbo

clare @ snyder.on .ca wrote in message
...
On Fri, 16 Jan 2004 09:11:16 -0500, Terry King
wrote:

Thanks for this:
Shear is directly proportional to the area. a 5/16" bolt would be
1.55 times more shear strength. Drilling it out to a clean hole
would also eliminate some unknown amount of bending that is going
on.

The grade 5 and grade 8 bolts would have more shear strength than
the usual soft steel but they would be much harder than the shaft
and tube so you would mangle them before the bolt sheared, NOT
what you want.
OK, Won't do that!


Generally a Grade 2 bolt is what you want for a shear pin, with a snug
fit. Which reminds me, I better pick up a couple sets for the old Noma
as I used the last set when I serviced it this fall.
And, this comment:
If the shear holes are getting battered, then perhaps it is the
movement that is contributing to the shear. Maybe new holes drilled
ninety degrees out of line of the old holes and some distance away?

OK, here's what I think I'll do (Comments and GotYas appreciated):

1. Drill existing holes out to 5/16". Temporarily install 5/16 Capscews
(smooth shank). This should stabilize the current rotational 'slop'.

2. Drill new 1/4" holes in the stabilized tube and bar, an inch or so
away and 90 degrees to the original holes. Install 1/4" mild steel
capscrews.

3. Remove 5/16 capscrews, run for a while.

4. If problem continues a lot, use the 5/16" (1.5 times the shear torque)
mild steel capscrews.

I have 800 feet of dirt road to blow, and although I walk the path in the
Fall and throw a lot of stuff off, I always seem to miss the odd piece of
fallen branch, rock etc. So I understand that I'm in a difficult
environment.

Meanwhile, my Grandkids are coming this weekend, and we've got a dynamite
sliding hill with no traffic except the occasional snowmobile...

Thanks for the help in understanding this!

The dirt driveway is not helping. At my last house the guy next door had a
gravel driveway, he had it plowed out of his driveway. When the town came to
plow I was "down wind" of him and the plow truck dumped his stones in my
nice driveway. I have since moved that was in a small way one of my reasons.
Now I have 350 feet on my own driveway with no stones donated from next door
much better.

On Fri, 16 Jan 2004 09:11:16 -0500, Terry King
wrote:

OK, here's what I think I'll do (Comments and GotYas appreciated):

snip

You seem to be studiously avoiding simply using the shear bolts
intended for the machine. They have two things going for them:

1 - They are heat treated to shear at a strength that is probably
going to prevent damage to the axle and tube. The heat treatment
leaves them on the brittle side because they shear cleanly on both
sides leaving a fairly flat, clean, break with a frosted appearance on
the ends of the at the breaks (a classic brittle shear). When mine
shear I push or tap out the remnant with a small punch, drop the new
bolt in, and tighten it just enough to lock the nylock nut on. The
bolt is slightly loose.

2 - Proper shear bolts will not "smear" on the broken ends as
ungrooved, smooth or threaded shank, common bolts will. The smeared
ends can inflict some damage on the holes and tube and could be a real
bitch to get out.

I have a unpaved driveway and the frost heave in Maine will generate
"new" rocks in places you thought they weren't. I don't mind the cost
of shear bolts (for my Home Depot MTD 8HP/24") at all when I look at
the big picture.

I have the skids on each side of my blower set as high as they will
go, that leaves about 1 or 1-1/2" of snow on perfectly flat level
ground. I can't get a completely clean area with a snow thrower and
really doubt that they were intended to be capable of doing that.



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In article , Jack Erbes says...

I have a unpaved driveway and the frost heave in Maine will generate
"new" rocks in places you thought they weren't. I don't mind the cost
of shear bolts (for my Home Depot MTD 8HP/24") at all when I look at
the big picture.

Main, heck. It don't look to good in NY either, Jack. I
am going to be studying the wheel configuration on the
Mars Rover because that is what's going to be required
pretty soon.

I have the skids on each side of my blower set as high as they will
go, that leaves about 1 or 1-1/2" of snow on perfectly flat level
ground. I can't get a completely clean area with a snow thrower and
really doubt that they were intended to be capable of doing that.

I actually had to purchase replacement skids for my Honda,
the originals were a bit on the weenie side but they were
getting the snot beat out of them. I now have the auger
well off the ground again.

Jim

==================================================
please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================

On 18 Jan 2004 08:48:26 -0800, jim rozen
wrote:

Main, heck. It don't look to good in NY either, Jack. I
am going to be studying the wheel configuration on the
Mars Rover because that is what's going to be required
pretty soon.

I'm glad to hear that because your storm is headed out way and we need
the snow. It is warming things up and we also need the moisture.
Take what you need and pass the rest North please.



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