PDA

View Full Version : Mower hub made of sintered steel?



MotorradMike
10-01-2014, 09:57 AM
Sears Craftsman mower needed a new blade and I found the "Star" mangled on the hub so had to buy a new one.
I believe the "Star" is meant as a shear feature.

http://i820.photobucket.com/albums/zz123/madmikemarr/Machining%20Mill/Mowerhub_zpsb00a62d1.jpg (http://s820.photobucket.com/user/madmikemarr/media/Machining%20Mill/Mowerhub_zpsb00a62d1.jpg.html)

I'm thinking of turning the remaining bits of the "Star" off the old hub and re-doing the hub arrangement so I don't have to pay $40 next time and wait 3 weeks.
I can file the steel OK, are there any tricks required to machine it?

TGTool
10-01-2014, 11:20 AM
I wouldn't expect any problems machining. You know it's soft enough to do its torque overload job. The only other factor might be abrasiveness and I wouldn't expect that either. There's no functional reason to have it for what the hub does and it would only add cost to the material.

CarlByrns
10-01-2014, 12:12 PM
Sears Craftsman mower needed a new blade and I found the "Star" mangled on the hub so had to buy a new one.
I believe the "Star" is meant as a shear feature.

http://i820.photobucket.com/albums/zz123/madmikemarr/Machining%20Mill/Mowerhub_zpsb00a62d1.jpg (http://s820.photobucket.com/user/madmikemarr/media/Machining%20Mill/Mowerhub_zpsb00a62d1.jpg.html)

I'm thinking of turning the remaining bits of the "Star" off the old hub and re-doing the hub arrangement so I don't have to pay $40 next time and wait 3 weeks.
I can file the steel OK, are there any tricks required to machine it?

Just buy a new hub- it's meant to shear. The OPEI standard is the blade is stopped by a 1" steel pin while at full speed. The blade, spindle, or crankshaft is not allowed to break or be damaged.

An new hub is way less expensive than a new engine (no one straightens cranks anymore) or the hospital bill when the blade snaps and chops a chunk of your foot off.

From the looks of the hub, there have been multiple blade strikes.

ahidley
10-01-2014, 01:29 PM
One fastener in the center with big washers on both sides is all ya need. When you hit something it will slip. It should rotate in the direction to tighten the fastener so it won't fall off.

I have seen some with fiber washes on both sides of the blade for the clutch/breakaway action.

38_Cal
10-01-2014, 02:35 PM
Or you can drill into the remains of the hub at each lobe of the drive "star", and press in five pieces of round brass to match the dia. of the blade star lobes. They should shear if you hit something nasty.

Highpower
10-01-2014, 02:44 PM
Never buy from Sears Parts Direct! Get the part number from their schematics and then buy elsewhere online.

http://www.ebay.ca/sch/i.html?_trksid=p2050601.m570.l1313.TR0.TRC0.H0.X58 1473301&_nkw=581473301&_sacat=0&_from=R40

MotorradMike
10-01-2014, 04:59 PM
Just buy a new hub- it's meant to shear.
From the looks of the hub, there have been multiple blade strikes.

I DID buy a new hub, as shown in the picture.
I'm a fan of shear protection but $40 and 3 weeks is over the top IMHO.
The mower gets beaten, as is the custom. It hits lots of rocks out here in the country.


One fastener in the center with big washers on both sides is all ya need. When you hit something it will slip. It should rotate in the direction to tighten the fastener so it won't fall off.

I have seen some with fiber washes on both sides of the blade for the clutch/breakaway action.

I like this, I've never had a blade break or a shaft bend in many years of cutting sketchy "lawns".


Or you can drill into the remains of the hub at each lobe of the drive "star", and press in five pieces of round brass to match the dia. of the blade star lobes. They should shear if you hit something nasty.

Thanks, I did not think of that - but too complicated.


Never buy from Sears Parts Direct! Get the part number from their schematics and then buy elsewhere online.

http://www.ebay.ca/sch/i.html?_trksid=p2050601.m570.l1313.TR0.TRC0.H0.X58 1473301&_nkw=581473301&_sacat=0&_from=R40

Yes, I searched on-line and found many attractive prices but they were all in the States, which is a problem.
Same part fits a Husqvarna, but we only have their chainsaws and dirt bikes here.

Thanks to you all!

MrSleepy
10-01-2014, 05:18 PM
I have an ally bodied 30yr old Hayter (golf course) rotary.

Underneath..it has a 20ins circular disc that has 4 bolt on.. freely rotating blades

http://s897.photobucket.com/user/MrSleepy123/media/hayterblades_zps24d82c37.jpg.html


If you hit anything...stumps ,pavement etc the blades spin out of the way,and the disc stops it going any further...very rugged.

Rob

Thomas Staubo
10-01-2014, 05:28 PM
I DID buy a new hub, as shown in the picture.
I'm a fan of shear protection but $40 and 3 weeks is over the top IMHO.
The mower gets beaten, as is the custom. It hits lots of rocks out here in the country.



I like this, I've never had a blade break or a shaft bend in many years of cutting sketchy "lawns".



Thanks, I did not think of that - but too complicated.



Yes, I searched on-line and found many attractive prices but they were all in the States, which is a problem.
Same part fits a Husqvarna, but we only have their chainsaws and dirt bikes here.

Thanks to you all!

Here you are Mike:
http://smallengines.ca/ecom.asp?pg=products&specific=jprrmocnrse&gotogrp=1874&gotopgnum=1

BTW, funny that you mention the OPEI standard, Carl.
But they can't possibly have heard about that standard at Electrolux (which makes Partner, McCulloch and Flymo mowers, among others).

Normally the blade hub should have a weak point, so it can shear before anything expensive or dangerous things happen.
I repair mowers for a living, and have never seen a blade hub break or shear, on one of those 53, 55 or 56cm mowers I mentioned above.
They are made of two steel parts welded together, and is so strong that it almost can't be broken.

If you hit a rock or a root with these, you severely bend the blade if you're lucky. But very often the crank shaft gets bent and/or the flywheel key shears.
When a customer delivers one of those mowers to us, we always check for bent crank shaft first.

MotorradMike
10-01-2014, 06:06 PM
Here you are Mike:
http://smallengines.ca/ecom.asp?pg=products&specific=jprrmocnrse&gotogrp=1874&gotopgnum=1


Son uva b****!!!!!!!!!!

I coulda got 2 fer 1 fairly quickly!

THAT is a fair price for a part they sell zillions of.

Website recorded.
Sadly, it took a guy from Norway to find it for me. I tried, really I did.

Thomas Staubo
10-01-2014, 06:09 PM
Son uva b****!!!!!!!!!!

I coulda got 2 fer 1 fairly quickly!

THAT is a fair price for a part they sell zillions of.

Website recorded.
Sadly, it took a guy from Norway to find it for me. I tried, really I did.

;)



.

Doozer
10-01-2014, 10:45 PM
One fastener in the center with big washers on both sides is all ya need. When you hit something it will slip. It should rotate in the direction to tighten the fastener so it won't fall off.

I have seen some with fiber washes on both sides of the blade for the clutch/breakaway action.

This is by far the best idea. You just need a big, think washer and a bolt to secure the blade.
Put your broken hub with the stripped nubs in the lathe, face it flat, and turn a pilot (step)
for the blade to center on. Never mind the nubbies. Just make a pilot that is a little thinner
than the blade. Then use a big washer and proper bolt. Thousands of lawn mowers are
made this way with no issue. The part with the nibbies shown is some engineer trying to
invent a solution to a non-existent problem. Above all else, keep it simple.
The best lawnmower (and `I still use it) is a Toro push mow from the late 60's.
It is 19" and super light weight. A nice feature is that the crankshaft only sticks out
of the bottom of the engine about 1-1/4". This means that crank will not bend when
you hit something. (Most cranks are 3-1/2" long or so). I have hit roots with it, and
I actually split the flywheel because of it. Crank and blade were fine though.
Tecumseh is kinda weird thou in their engineering plan. The engine uses a steel
flywheel key, not an aluminum key like the Briggs. So hitting something is most
likely to split the flywheel. Old flywheels were all aluminum. Newer design has a
steel hub cast into the center where the taper and keyway are. This saves the
flywheel from cracking, but I still use my own aluminum key.
Another nice feature is the muffler exits under the deck. It makes it a bit quieter,
but slight downside is the muffler rots out faster. I am on my 3rd of 4 new old
stock Toro mufflers that I happen to have for it. Also odd is that it has an S-shape
blade on it. I can't see why it is any better. I have not run across a spare one yet
in my travels. I guess if it gets worn to a nub, I will replace it and the hub with a
19" straight blade.
All quirks aside, I like the mower because it is so light compared to newer ones.
I even like the smaller diameter push handle, it is 5/8" instead of the usual 7/8"
ones. One day I will TIG up the many holes in the deck and give her some
proper love. Now it gets by with sheet metal patches screwed over the holes.
Good luck with your mower.

-Doozer

bruto
10-02-2014, 12:51 AM
I have an ally bodied 30yr old Hayter (golf course) rotary.

Underneath..it has a 20ins circular disc that has 4 bolt on.. freely rotating blades

[url]http://s897.photobucket.com/user/MrSleepy123/media/hayterblades_zps24d82c37.jpg.html[/url


If you hit anything...stumps ,pavement etc the blades spin out of the way,and the disc stops it going any further...very rugged.

Rob]Long ago I had a 2-stroke Jacobsen that had a similar blade. Very effective, and it also served as a big flywheel. The Jacobsen motor eventually died, as I recall - it had come from the dump to start with anyway. But I was always surprised that this system was not more widely used. The little knives were easy to sharpen and replace, and as I recall they were reversible too.

Prokop
10-02-2014, 07:29 AM
I don't buy the sheering of the star, it is driven by belt after all and the belt would slip before anything worse could happen.

I farked myself weekly with a mower that had stars tomount blades on too - it was no match for the farm land we live on.

Anyway, the spindle is easy to turn, I done it just for fun and lathe practice on spent spindles.

MotorradMike
10-02-2014, 08:50 AM
Doozer, that's exactly what I am going to do for the next time.(spacer that centers the blade on the hub adapter.
I agree that the star shear is over Engineering.


I don't buy the sheering of the star, it is driven by belt after all and the belt would slip before anything worse could happen.


The hub is keyed to the motor shaft, the pulley on the hub drives the mower front wheels.