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Author Topic: Got snow? And what's wrong with this picture?  (Read 16321 times)

Offline Geezer

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Got snow? And what's wrong with this picture?
« Reply #25 on: 02/01/2011 23:37:14 »
It is hard to tell...  and your description is a bit sparse...  to say the least. 

I've always found a good shovel was quite effective, and then one could neatly pile the snow next to the road or driveway, rather than blowing it onto the neighbor's property.

A couple of things I might question.

You've apparently done maintenance on the bearings.  I would consider if it was better to put the grease fittings on the outside of the snow blower rather than the inside...  except perhaps there would be a risk of smashing them into something, or dragging on the side.  But at least one could protect them from the snow.  IS THE GREASE FITTING ON THE LEFT SIDE MISSING?

The two spirals would tend to separate in the middle, so they couldn't be "floating" on the drive shaft without some kind of washers or spacers.  The attachment is unclear.

I can't tell if the single vertical support in the middle would be adequate.

The fan on back appears to turn counterclockwise.  I'm trying to figure out the benefit of having an angled blade vs a flat blade.  In fact it almost appears as if that has been modified.  I think I would have added a support to the blade on the "back" side rather than the "front" side as the angle in the photo looks like it would tend to blow the snow backwards rather than upwards (oh, I see someone else made that comment, anyway, it is probably ok).

Good catch on the grease fitting. Yes, it is missing. But that's not the problem I'm referring to.

The scrolls are attached to the shaft by a bolt that also acts as a shear pin to prevent damage if something wedges the mechanism. The "upchucker" actually rotates clockwise. The blades are flat, with a flange on both sides, although it's a bit hard to see that in the photo. So, no particular problem there either.

It's not a trick question btw, it's simply a question of kinematic geometry.

 

Offline Geezer

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Got snow? And what's wrong with this picture?
« Reply #26 on: 04/01/2011 22:48:05 »
I'm surprised I have not been able to Hooke a mechanically minded person in this joint that is able to answer my question.
 

Offline peppercorn

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Got snow? And what's wrong with this picture?
« Reply #27 on: 04/01/2011 23:11:54 »
I'm surprised I have not been able to Hooke a mechanically minded person in this joint that is able to answer my question.
The UJ on the left end of the shaft is clearly folded far too tight (at right ankle) to turn, but as I;m not totally sure where the prop-shaft bit actually locates on the machine I can;t tell if this would be an actual problem in use.

I would guess it couples to the left end of the screw - and the UJs might be on too tight a turn operate.
« Last Edit: 04/01/2011 23:14:22 by peppercorn »
 

Offline Geezer

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Got snow? And what's wrong with this picture?
« Reply #28 on: 04/01/2011 23:24:42 »
The drive shaft connects the PTO (power take off) shaft at the back of the tractor to the shaft that supports the impeller (upchucker) thingy. That shaft sticks out the back of the blower, so you can't see it in the piccy.

In operation, the joints would not be folded back the way they are in the piccy. They would have a relatively small angle of articulation. There is nothing wrong with the joints though.
« Last Edit: 04/01/2011 23:26:51 by Geezer »
 

Offline SeanB

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Got snow? And what's wrong with this picture?
« Reply #29 on: 06/01/2011 19:14:08 »
I would guess that it is possible to bring in too much snow or slush for the ejector to remove without becoming jammed, That would also require the frangible connection on the auger as otherwise it will be possible to sieze the gearbox with the load imposed on it, and a drive shaft that is free at the non driven end is not a safe thing to be near, or within range of the debris that it causes.
 

Offline Geezer

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Got snow? And what's wrong with this picture?
« Reply #30 on: 06/01/2011 19:33:31 »
Ah, right! Yes, there is a safety tube that fits over the driveshaft to prevent bad things from happening in the event of a joint failure.


However, that's not the problem I'm referring to either  :D
 

Offline CliffordK

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Got snow? And what's wrong with this picture?
« Reply #31 on: 07/01/2011 04:11:55 »
Your photo isn't very clear of the "pickup" area.

Thanks for clarifying the direction of the blower, clockwise. 

There is a shield in the upper left of the pickup area (I can't see how far it extends downward), which protects the snow as it enters the auger and is flung upwards. 

There is also a vertical bar holding the differential in the middle from the top.

Any snow that gets shoved into into the upper left of the pickup area then gets stuck between the shield over the pickup, and the post, with no place to go.

Depending on how far down that shield extends, the snow from the right will get picked up better than snow from the left.

Were you the one that asked about wet snow vs dry snow?  If that is your problem...  you need to get your hair dryer out and dry your snow   ;D
 

Offline Geezer

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Got snow? And what's wrong with this picture?
« Reply #32 on: 07/01/2011 05:11:40 »
Your photo isn't very clear of the "pickup" area.

Thanks for clarifying the direction of the blower, clockwise. 

There is a shield in the upper left of the pickup area (I can't see how far it extends downward), which protects the snow as it enters the auger and is flung upwards. 

There is also a vertical bar holding the differential in the middle from the top.

Any snow that gets shoved into into the upper left of the pickup area then gets stuck between the shield over the pickup, and the post, with no place to go.

Depending on how far down that shield extends, the snow from the right will get picked up better than snow from the left.

Were you the one that asked about wet snow vs dry snow?  If that is your problem...  you need to get your hair dryer out and dry your snow   ;D

Good shot! But that's not it either  :D

BTW, the "differential" is just a simple gearbox. The auger shaft runs straight through it. The blower actually operates reasonably well, as long as the obvious mistake is addressed. You might want to go back and take a look at some of the clues I left.

Happy hunting!
 

Offline CliffordK

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Got snow? And what's wrong with this picture?
« Reply #33 on: 07/01/2011 08:34:18 »
It looks like it has a minimum cut of a couple of inches which is probably appropriate for working on gravel.  I might consider adding a floating scraper for working on pavement, although snow does give better traction than ice.  I don't like the bolt heads sticking out the bottom of the blade, but they probably don't hurt anything as they should be more or less kept off of the ground by the feet on either side. 

I can't tell the width.  In the video you linked, it appears as if the blower is narrower than the tractor, causing the rear tires of the tractor to be hitting the snow bank, although it appears to be offset a little which makes up for it.

My tractor has 9 forward and 3 reverse gears, so I can set the speed pretty well.

You seem to hilight:
Quote
mechanical bent
You've also said
Quote
I'm surprised I have not been able to Hooke a mechanically minded person in this Joint that is able to answer my question.

Your PTO linkage looks a little dry.  Don't they have any grease where you're at?  It should be designed to give you adequate slippage and forward/backward adjustment.  I'm assuming the length is matched to the device.

Your tractor 3 pt hitch is designed for dragging forward, so reversing may be problematic.  But, I would think the tractor part would be sturdy enough.  You don't show any photos of the blower hitch, but I'm guessing that it can deal with the stresses that it creates,although the one in the video hangs back a lot. 

The snow auger screws look surprisingly flimsy. 
 

Offline Geezer

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Got snow? And what's wrong with this picture?
« Reply #34 on: 07/01/2011 15:18:07 »
Nope. You are still missing it  :D

Try again.
 

Offline imatfaal

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Got snow? And what's wrong with this picture?
« Reply #35 on: 07/01/2011 16:52:24 »
Is there an extraneous lump (looks like a bolthead) coming out of the LH universal joint on the brown/grey connecting rod - it doesn't look as if the left hand side of that rod could straighten up.
 

Offline Geezer

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Got snow? And what's wrong with this picture?
« Reply #36 on: 07/01/2011 17:33:47 »
Is there an extraneous lump (looks like a bolthead) coming out of the LH universal joint on the brown/grey connecting rod - it doesn't look as if the left hand side of that rod could straighten up.

If you mean the light coloured thingy that's on the cross piece of the LH U-joint, that's a Zerk fitting for injecting grease.

It's about acceleration.
 

Offline CliffordK

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Got snow? And what's wrong with this picture?
« Reply #37 on: 08/01/2011 03:51:03 »
Quote
I'm surprised I have not been able to Hooke a mechanically minded person in this Joint that is able to answer my question.

Never heard of Robert Hooke before...  But according to Wikipedia.

http://en.wikipedia.org/wiki/Universal_joint#History

Quote
between 1667 and 1675, Robert Hooke analysed the joint and found that its speed of rotation was nonuniform
[...]
Hooke proposed a solution to the nonuniform rotary speed of the universal joint: a pair of Hooke's joints 90° out of phase at either end of an intermediate shaft.

So, one has to determine what that means. 

And one finds that the two yokes on the shaft should be lined up the same, so the joints as you progress down the shaft should be out of phase.

http://www.custompistols.com/cars/articles/ts_ujoints.htm


So, the U-joints in your photo are "in phase", instead of "out of phase".  This would tend to amplify the non-uniformity of the joint, and would tend to cause some pounding or surging.

Thank You.

One learns something new every day!!!!!!!!!!!!

That must be why you use the name "Geezer"...  Hooke was before my time!!!!   And, now is virtually obsolete!!!
« Last Edit: 08/01/2011 04:01:53 by CliffordK »
 

Offline Geezer

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Got snow? And what's wrong with this picture?
« Reply #38 on: 08/01/2011 04:15:41 »
Yeah!!!

U joints (or Hooke's joints) are not "constant velocity" joints (like the ones used in most front wheel drive cars).

However, if there are two of them at opposite ends of a shaft and the phase is correct, as long as the "bend angles" of each U joint are the same, the input and output velocities will be the same. Another interesting aspect of this is that the axes of the input and output do not need to be parallel. It's only the magnitude of the bend angles that need to be equal.

Of course, the bit of the shaft between the U joints still accelerates and decelerates twice during every revolution, but the shaft has a lot less inertia than the mechanism it's driven by, or trying to drive.

BTW, Hooke's joints are anything but obsolete. Although they are not used so much on private automobiles, they are still used extensively in commercial and industrial applications. The reason for this it that they have much greater torque capacity per volume and cost compared to CV joints.

Come to think of it, I think they are still used on F1 racing cars.
« Last Edit: 08/01/2011 04:28:19 by Geezer »
 

Offline Airthumbs

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Got snow? And what's wrong with this picture?
« Reply #39 on: 08/01/2011 09:33:29 »
I know, I know, I know, there isn't any snow  ;D
 

Offline SeanB

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Got snow? And what's wrong with this picture?
« Reply #40 on: 08/01/2011 16:16:52 »
Almost every car has at least one, in the steering column, to change the drive angle to match whatever steering mechanism they use, and to enable you to adjust the steering wheel height.
 

Offline graham.d

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Got snow? And what's wrong with this picture?
« Reply #41 on: 08/01/2011 16:29:57 »
I know that large angle (and angle movement) CV joints on front wheel drive cars are different from these (I think they have a some sort of sliding spline arrangement - I had one fail on an Audi 100 many years ago) but this sort of "U joint" used to be common on either end of the prop shaft for rear wheel drive cars. As its been many years since I've had to lie underneath cars to do my own maintenance, this may have changed, but BMW and Mercedes persist with RWD so it may still be the same. Damn, its too dark to check now :-). I used to call these CV joints too but I appreciate they are not, strictly, except when the angle is neglibly small.
 

Offline Geezer

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Got snow? And what's wrong with this picture?
« Reply #42 on: 08/01/2011 18:23:17 »
Yes, CV joints use something that looks like Salvador Dali's idea of a ball bearing where the balls are prevented from rotating. I don't like them much because the force is transmitted by line contacts on the surface of the balls. I managed to compression weld one on my VW while driving, slightly aggressively, up Oak Creek Canyon in Arizona.

U-joints (usually) spread the load over needle bearings and seem to be much more satisfactory, except that they create velocity fluctuations, which is a real problem at large angles.

To complicate matters even more, there are constant velocity joints that consist of an assembly containing two U-joints and a mechanism to ensure that the bend angles of the two joints are equal. I know this because I had to repair one on a Ford Bronco. I'd never seen anything like it before then.

U-joints are still common on the prop shaft of rear wheel drive vehicles. Unless the shaft is short, or the rear suspension has a lot of travel (like the Bronco), U-joints work very well.

For those unfamiliar with the road in Oak Creek Canyon, this is the bit where I banjaxed my CV joint.

« Last Edit: 09/01/2011 01:06:01 by Geezer »
 

Offline SeanB

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Got snow? And what's wrong with this picture?
« Reply #43 on: 09/01/2011 10:18:49 »
Rear wheel drive vehicles nowadays tend to use CV joints at the rear half shafts to allow the rear suspension to be independent, only tied by a anti roll bar. This gives a smoother ride, and often the drive is supplied via CV joints as well.

I have met 2 style of joints, one uses a large ball that slides in a slot in the inner and outer races that is normal to the direction of rotation, while the other uses a 3 spoked shaft with a bearing on each spoke, that runs in a slot in the outer member.
 

Offline CliffordK

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Got snow? And what's wrong with this picture?
« Reply #44 on: 26/08/2011 08:19:30 »
I was looking at my Ford Pickup today.

It has three Universal joints, instead of two.

The first one is pretty closely aligned with the transmission.  But, it would seem that it is not a good idea to have an odd number of joints.
 

Offline peppercorn

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Got snow? And what's wrong with this picture?
« Reply #45 on: 26/08/2011 13:02:12 »
I was looking at my Ford Pickup today.

It has three Universal joints, instead of two.

The first one is pretty closely aligned with the transmission.  But, it would seem that it is not a good idea to have an odd number of joints.

Perhaps the two nearest the tranny aren't completely free UJs and are designed to allow for lateral movement in the drive.

My car is rear engined and has 'rubber-doughnuts' connecting the half-shafts to the transaxle.  These allow for the changing geometry of the rear suspension which requires the driveshafts to elongate and compress whilst rotating.

(Anyone hazard a guess what this car is?)
 

Offline graham.d

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Got snow? And what's wrong with this picture?
« Reply #46 on: 26/08/2011 13:42:03 »
VW beetle??
 

Offline imatfaal

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Got snow? And what's wrong with this picture?
« Reply #47 on: 26/08/2011 14:14:23 »
I reckon Pepper is a secret 911 driver
 

Offline peppercorn

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Got snow? And what's wrong with this picture?
« Reply #48 on: 26/08/2011 14:35:32 »
No. Neither.

I did test-drive a 944 once that a work colleague was selling, but being from 1980ish it was too new to get free UK road-tax and too old to be reliable/inexpensive-to-maintain. ...  It was like driving a go-cart though!!
 

Offline imatfaal

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Got snow? And what's wrong with this picture?
« Reply #49 on: 26/08/2011 16:05:43 »
Ok - so it could be a smartcar (great city car), or a skoda (and not one of the uber-reliable new ones - the dodgy 80s ones, what do you call a skoda with a sunroof), a hillman imp (huge reverse chic) or what I really hope is that it is a renault-engined alpine. 

If it is an alpine I will wave at all I see (cos there probably are only one or two in London) in the hope of saying hello!
 

The Naked Scientists Forum

Got snow? And what's wrong with this picture?
« Reply #49 on: 26/08/2011 16:05:43 »

 

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