Reversing the direction of my Belt Sander?...

[Batpig]

My Dear Friends-in-Disaster,

I am attempting to modify my 900w Ozito Belt Sander so that it can be thrown into "reverse" by way of a secondary Switch (that would have to be DPDT), but all of my experiments thus far in the endeavour have met with less-than-satisfactory results.

As you can see from the first photo below, the motor is a simple, series-wound "Universal" device. One of the blue wires runs from the Power Trigger into one end of one of the Stator-half Coils, and then emerges at the other end of the same Stator-half as a grey wire, which feeds one of the Brushes. After travelling around the Armature coils, the current then finds its way down into the other Brush, and hence down along the other grey wire into the other Stator-half's coils, before emerging in the other blue wire which runs back to the Power Trigger. Finally, a capacitor lies in parallel across the circuit at the Power Switch...

110508

Now, the thing is - I have tried everything that I can think of, including every combination of the following items in their normal and reversed positions:
a) Brush feeds from the Stator
b) Stator feeds from the Power Trigger
c) The Capacitor across the Power Switch (just in case it had some unmarked Polarity about it...)

The results so far are that the motor does actually run in reverse only when the Brush-feeds are switched, but only very, very roughly, and to the accompaniment of glorious sheets of flame billowing out of the side vents under the air-pressure of the cooling fan (I will actually try to take a photo if I go to the trouble of wiring everything back up again...:D).

So - am I missing something fundamentally simple?...:?

I pulled my A/C Drill apart to have a look at its setup for Reverse, and the reversing is enabled by an altogether separate Lever-Switch to the Power Trigger. There are four wires hooked up to this Lever-Switch - yes, you guessed it; the two wires from the Stator-halves, and the two wires from the Brushes. The Lever-Switch obviously just swaps over the combination of connections between the Stator-halves and the Brushes...

One small thing I have noticed that might possibly hold the key to the whole puzzle is the fact that the wires running up to the Armature coils from the Commutator are spiralled in one direction. You can see what I mean from the photo below:

110509

Perhaps this spiralling creates a rotational torque-offset in one direction only that biases the Armature upon energisation to start spinning in one particular direction. I took my reversible Drill apart to have a look at the corresponding wires running up from its Commutator, and whilst they do spiral up, they don't seem to be quite as all one-way in the direction of their spiralling as they are in the Belt Sander. Perhaps this is the cause of the whole problem?...

Anyhow, I know there's some very clever Cookies out there! Might one of you have some ideas that might prevent the seemingly imminent and fiery demise of the otherwise innocent Ozito? :-

Many Thanks,
Batpig.

[Jim Carroll]

Most single direction armatures are wound in such a way that if you did reverse the stator you would get very little tourque.

Machines like sanders are single direction and the lead in the windings gives more torque in one direction.

I would say it would not be satisfactory and in such a cheap machine a waste of time.

[malb]

There are a couple of things involved here.
To reverse the motor rotation, you need to reverse the mag fields greated by the armature windings relative to those produced by the stator windings. As you surmised this is done by reversing the wires at the brush holders. So why does it run rough and arc a lot when you do this?
The armature is 'timed' i.e. the armature windings are advanced part of a segment relative to the comutator segments to maximise torque and minimise arcing. When you reverse the direction of rotation, this timing is effectively retarded instead of advanced reducing torque and increasing arcing.
To reverse the motor efficiently, a different armature with the timing reversed would be required. To make it switchable F/R, then a neutral timed armature can be used, but at the expense of an increase in arcing and a reduction in torque in both directions.

Incidently, why do you want a F/R switch on belt sander?

[Skew ChiDAMN!!]

So he can back it over the line at the Belt Sander Drag Races?

(Surprisingly, the Ozito's do quite well at them. DAMHIKT. :-)

[Master Splinter]

Actually, with the flames shooting out as it is backed up, that could look quite impressive at the belt sander races. Add a rubber belt instead of a sanding belt, put some oil down, and you could smoke the tyres, too....????

[Batpig]

Dear Chaps,

Machines like sanders are single direction and the lead in the windings gives more torque in one direction.

So why does it run rough and arc a lot when you do this?
The armature is 'timed' i.e. the armature windings are advanced part of a segment relative to the comutator segments to maximise torque and minimise arcing.

To make it switchable F/R, then a neutral timed armature can be used, but at the expense of an increase in arcing and a reduction in torque in both directions.

That's it guys! It's that spiral "wind-up" of the wiring from the Commutator that you can see in the second photo of my original post...

Makes sense, too. Well, that's that then, as they say. C'est La'Vie...:-


Incidently, why do you want a F/R switch on belt sander?
Malb, I've got quite a few external mitred corners in some Skirting that I want to sand back with varying degrees of "bias" to one or the other of the two intersecting pieces in order to get them to apex at their absolute join-lines. Because I need to sand away from the corner in both directions (in order to not splinter the end of the other intersecting piece), and because I can only get the sanding belt to run out to the edge of the Sander on the non-belt-drive side (which must be pointing down to get to the bottom of the Skirting), I'd therefore like to be able to reverse the direction of the sanding belt because the belt-drive-cover must obviously always point upwards (Hope that makes sense...:cool:)


So he can back it over the line at the Belt Sander Drag Races? (Surprisingly, the Ozito's do quite well at them. DAMHIKT. :-)
That is ultra,ultra-sharp Skew - especially as there was only three or four minutes between Malb and you!:2tsup:


Actually, with the flames shooting out as it is backed up, that could look quite impressive at the belt sander races. Add a rubber belt instead of a sanding belt, put some oil down, and you could smoke the tyres, too....????
That's pretty sharp too Splinter! You guys are Men On Fire tonight!..:wink:

Many Thanks,
Batpig.

[ian]

Malb, I've got quite a few external mitred corners in some Skirting that I want to sand back with varying degrees of "bias" to one or the other of the two intersecting pieces in order to get them to apex at their absolute join-lines. Because I need to sand away from the corner in both directions (in order to not splinter the end of the other intersecting piece), and because I can only get the sanding belt to run out to the edge of the Sander on the non-belt-drive side (which must be pointing down to get to the bottom of the Skirting), I'd therefore like to be able to reverse the direction of the sanding belt because the belt-drive-cover must obviously always point upwards (Hope that makes sense...and if you do succeed in reversing the motor, you will also have to reverse the belt.
Sanding belts are designed to run only one way — it's on account of how the join is made
reversing the motor direction will likely result in a standard belt breaking within a few seconds

[BobL]

and if you do succeed in reversing the motor, you will also have to reverse the belt.
Sanding belts are designed to run only one way — it's on account of how the join is made
reversing the motor direction will likely result in a standard belt breaking within a few seconds

I also used to believe that belts will break if used in reverse. I have been reversing my belts for years to clean them with that rubberised stick stuff. Now and again I'd leave them on reversed and noticed they never broke when used in this was and so I have been using them in either direction and cannot ever recall breaking one.

[Claw Hama]

Batpig, can you just get away using an orbital or random orbital in those tight spots?

[elkangorito]

The direction of Universal "series" motors can be reversed.

You can do this by swapping the leads to the armature or the magnetic fields but not both.

The reason why you are seeing lots of sparks when the motor is reversed is because the brushes are "going against their grain". If you run the motor in reverse for a long period of time & preferably with a load, the sparks will soon disappear. After you've done this, it would be advisable to "clean" the commutator with a piece of fine grade emery cloth, until the commutator is shiny. When you've done this, give it a wipe over with a clean rag soaked in alcohol (to remove the filings).

[Lignum]

I also used to believe that belts will break if used in reverse. I have been reversing my belts for years to clean them with that rubberised stick stuff. Now and again I'd leave them on reversed and noticed they never broke when used in this was and so I have been using them in either direction and cannot ever recall breaking one.

:2tsup: Same here. Reversing the belt gives you more "sharp" grit, so you get an extra 15-20% life out of it. And they have never broken on me either. Its the way to go. And when sanding tops etc, I hold my sander back to front and sand into the belts direction, much like a drum sander. I get better results that way.

[Batpig]

Dear Guys,

and if you do succeed in reversing the motor, you will also have to reverse the belt. As you would well know, that is definitely doable within a few seconds Ian.


Batpig, can you just get away using an orbital or random orbital in those tight spots? Maybe Claw, maybe... But the "action" is not uniquely in the preferred direction away from the external corners. But Beggars can't be Choosers, as they say. A straight Orbital would be the better of the two you suggest, because the edge of the backing-plates are straight and usually made of metal, compared to the more vulnerable round rubber that is on the bottom of my Mak ROS.


The reason why you are seeing lots of sparks when the motor is reversed is because the brushes are "going against their grain". If you run the motor in reverse for a long period of time & preferably with a load, the sparks will soon disappear. I know what you're saying El', and I have persevered a bit to see whether the spark situation in reverse has been abating, but I do think that the pronounced spiral wind-up of the Armature leads mentioned previously is a dominant and limiting factor. I have noticed that my Drill is both a little slower, as well as a little "sparkier", in reverse, and it doesn't even have as much "wind-up" in the leads to the coils that are running from its Commutator as the Sander has. I'm playing it by ear, though. I have to be careful that I don't melt the Sander's housing before I "bed" its brushes into reverse-direction use...

Many Thanks everyone,
Batpig.

[malb]

I had a fair bit of time as a metal polisher working with belts up to150mm wide x 3.6m long in a wide variety of grits and abrasive. Most of these belts are marked with an arrow to indicate run direction, but this optional rather than essential.

In metal polishing, the belt is swapped frequently as you work through the belt grades, and the arrow helps to ensure that you mount the belt in the same direction as it previously was, or conversely in the opposite direction. Why? To get max life from a belt you run it through a fair portion of it usefull life in one direction, then once it starts to 'go off'' , reversing the rotation gives access to the back edges of the abrasive grains, and extends belt life by about 35 to 40% over single direction only use.

Probably saw an average of one belt actually break out of maybe 150 worked to death in a week, but these were normally due to to the belt snagging or being cut by the workpiece, rather than the joint failing. Quite interesting to see a 3.6m belt thrash itself to death driven by a 5HP motor with people trying to dodge the flying strands and stop the machine.

[eddie the eagle]

...asks...am I missing something fundamentally simple?...:?


Hi Batpig,

COming from a former industrial engineer, while it's possible to reverse direction of the motor, the threads on all the shafts, etc... are designed to tighten under load.

It's probable that if you reverse the direction of the motor, you'll start undoing things unintentionally.

That is, unless every connection is splined/keyed into place.

Cheers,

eddie

[gerhard]

Hi Michael,

you'll wreck the sander for sure, so don't attempt this. The optimisation of the armature coils and the resulting magnetic field, which is rendered into a time-lag when used in reverse, is mentioned as an argument against doing this several times in the other posts, and rightly so. But all other things go in reverse too, like the drive train, the belt system, the cooling air flow and the dust suction fan.

For instance, when you look at the cooling fan mounted on the armature, you see the blades curved in a certain way. That means they are optimised for scooping the air from the direction of the commutator and the rotor coils towards the fan itself. Run in reverse, curved blades only produce a fraction of the designed and calculated airflow. Forthermore, the air is supposed to first cool the commutator and then the coils. If the air is heated up after passing the coils, the commutator will run too hot and there is already much more sparking then this system was designed for in the first place.

As for the sanding belt run in reverse, think of a chain saw run in reverse. Normally the chain is drawn through the wood by the motor driven sprocket. Only the blade's bottom part and the sprocket take the strain. The blade's top part and the star wheel in front are meant to guide the chain round and back to the sawing process again. Experienced users are seen to use the blade's top part as well, to saw little branches from felled trees in very quick expert movements. But they know that the machine can not take too much strain this way, because the pulling force is transfered from the sprocket to the star wheel, which has a very flimsy to an almost non-existing bearing system.
On a belt sander run in reverse, the pulling takes place at the upper belt part and the pulling strain on the sanding bottom part of the belt sander is transfered from the hind rubber coated drive roller to the front guide roller. This roller has a decent bearing system and it can take this strain, and traction from the hind roller will take place just as good whith this roller as an inbetween. But the guide roller has a steering function, taking care of the proper belt track. With pulling force on this steering roller, the belt tracking will probably go wrong very quickly and adjusting will be very finnicky.

In reverse the dust will not be drawn away at the back by the suction fan, but spewed out from underneath the belt at the front. The fan itself will not work properly, either. Centrifugal fans do not blow instead of suck when rotated in reverse, but the shape of their enclosure determines that their designed efficiency works in one direction only. Run the other way, the displaced amount of air may be 30% or less of nominal output.

The drive train is probably a toothed belt as a primary step, and a set of gears as a secondary step to drive the hind roller. The toothed belt will run fine in both directions, in worst case a pulley may loosen itself when there is a thread involved for fixing or securing. The gears, however, may be ground helical. There is always a slight axial thrust component generated by helical systemes, which is absorbed by some of the bearings. This axial thrust will point in opposite direction when such gears run in reverse, which may be harmful -or not. I don't know your type and make of machine, so i can't determine if it is or if it ain't..

Sanding belts are cut from large rolls of fortified linen strips, carrying sprinkled and glued abrasive grains. At both ready cut glue joints of a length of strip, the grains are rubbed off, in order to have a dependable adhesive contact between fabric and fabric. The fabric overlaps on this joint and the inside overlap must point in the rotating direction of the belt. When the rubber coated drive roller pulls at the joint, the overlap will take the strain without fraying, when pointing in the right direction. With the belt mounted the wrong way, the pulling rubber of the drive roller may peel off the glued overlap bit by bit at every loop pass, which may eventually make the sanding belt snap or tear. So there's more involved than just a reversing switch, running in reverse also means having to mount the belt in reverse.

And than there's the base plate, which is often a heat treated steel plate or some sort of graphite coated fabric. It is fixed at the leading edge only, to allow heat expansion and shrinkage at the trailing edge. With the sanding belt running in reverse, a graphite coated piece of fabric would just crumple and tear loose. But with a steel plate, the belt could snag behind its loose trailing edge, with sure damage to the belt and plate and possible damage to your health. Since the inside joint overlap of the sanding belt must point in the running direction and will collide head on with the loose trailing edge of the plate when run in reverse, chances on snagging are big.

So, all in all, as said in the other contributions above, the disadvantages vastly outnumber the advantage, so do not invest in the effort.

greetings!

gerhard

[ian]

Malb, I've got quite a few external mitred corners in some Skirting that I want to sand back with varying degrees of "bias" to one or the other of the two intersecting pieces in order to get them to apex at their absolute join-lines. Because I need to sand away from the corner in both directions (in order to not splinter the end of the other intersecting piece), and because I can only get the sanding belt to run out to the edge of the Sander on the non-belt-drive side (which must be pointing down to get to the bottom of the Skirting), I'd therefore like to be able to reverse the direction of the sanding belt because the belt-drive-cover must obviously always point upwards (Hope that makes sense...:cool:)Batpig

I'm having trouble getting my head around this...

I can't see how you can sand both sides of a mitred corner without removing at least one piece (or both pieces) of skirting from the wall.

Can you post a sketch?

[Skew ChiDAMN!!]

I can't see how you can sand both sides of a mitred corner without removing at least one piece (or both pieces) of skirting from the wall.

Perhaps he doesn't mean sanding the mitred edge, but the outside faces? :?

[Batpig]

Dear Gentlemen,

It's probable that if you reverse the direction of the motor, you'll start undoing things unintentionally.
I did have that in mind early in the piece Eddie, but bear in mind that I was only ever in the experimental stage. Given the thing's asking-price (which was all of $59 a couple of years ago :wink:), it was well worth taking the punt...


So, all in all, as said in the other contributions above, the disadvantages vastly outnumber the advantage, so do not invest in the effort.
Ahhh... The Supreme Court of Power-Toolery has spoken! I hear and obey...


I can't see how you can sand both sides of a mitred corner without removing at least one piece (or both pieces) of skirting from the wall.

Perhaps he doesn't mean sanding the mitred edge, but the outside faces?
"Yes! Yes! Yes!" (in Meg Ryan's voice...) Sorry I wasn't clearer Ian :-. Thanks Skew! So few words, yet so much sketching-time saved...:2tsup:

My Best Wishes to you all,
Batpig.

[ian]

<TABLE border=0 cellSpacing=0 cellPadding=6 width="100%"><TBODY><TR><TD style="BORDER-BOTTOM: 1px inset; BORDER- 1px inset; BORDER- 1px inset; BORDER-RIGHT: 1px inset" class=alt2>Originally Posted by ian http://woodworkforums.cyanide-static.com.au/images/button2/viewpost.gif (http://www.woodworkforums.com/showthread.php?p=995983#post995983)
I can't see how you can sand both sides of a mitred corner without removing at least one piece (or both pieces) of skirting from the wall.



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Originally Posted by Skew ChiDAMN!!
Perhaps he doesn't mean sanding the mitred edge, but the outside faces?

"Yes! Yes! Yes!" (in Meg Ryan's voice...) Sorry I wasn't clearer Ian :-. Thanks Skew! So few words, yet so much sketching-time saved...:2tsup:Your skirtings must be a whole different profile to mine.
If I were to sand the outside faces of my skirtings the difference in thickness and profile would be so so obvious

[Batpig]

Dear Gents,

Skew & Splinter - this one's for you! Enjoy...

110774

Gerhard - I've gotten so used to your typically superb posts that I forgot to commend you for your last effort, which was as thoroughly thorough as ever...:2tsup:

Best Wishes,
Batpig.

P.S. Did I mention the smell of the thing in reverse? No?... Then picture Robert Duvall in a Cavalry Hat, and substitute the word "napalm" with "carbon brushes"...

[Skew ChiDAMN!!]

Skew & Splinter - this one's for you! Enjoy...

110774

:lolabove: Now that's an Ozito I'd keep! :U

[Weekend hack]

Hi Batpig.

That pic shows how all my ozitos have worked straight out of the box.

The reason everyone is saying not to do this is because you will tear a gapping big hole in the fabric of time.
Just from the pic it is obvious you are close to the point of achieving real time travel. :D

If you do manage to synchronize the fields we could all be in strife.

However, a drill is reversed from the switch not the brushes. The whole magnetic circuit is reversed.
I would assume the magnetic field / flux created in the series design of the motors outer fields and armature / rotor are corresponding to one another.
If you reverse the brush connection you are effectively only reversing half of the circuit.
This may be the cause of the arc welder effect.

Brushes are usually beded in in motors with a talc or chalk type substance.
While running, the chalk is placed against the commutator. the fine powder abrasively beds the carbon brushes in and reduces the arc.

Your gonna need a lime pit to get enough chalk to bed that thing in.:D

Best of luck.

[rrobor]

It wont work. In the old days you could reverse wires and all was well, now to be more efficiet the windings of commutator and field are such you get maximum output for minimum intput. If you reverse that, what you get is poor output for maximum input hense the flames. My advice is instead of going left to right all the time, try pointing the thing in the other direction.

[gerhard]

Good Lord, what sparks! I've never seen such a violent display in a power tool! When the motor does that, its armature is definitely not wound "symmetrically" but rather offset for optimal efficiency in one direction. For a motor to run equally well in both directions, the position of each armature coil has to match the position of its two opposed commutator strips in a symmetrical way, so there is no bias in either running direction. In this motor, this is obviously not the case and it is therefore specifically designed to run in one direction only.

This phenomenon is totally different from normal brush sparking in a motor suited for both directions, when it is reversed after having run in one direction for some time. Since the brushes must have some play in their holders in order to react quickly to trapped dirt between brush surface and commutators (making the brushes lift a bit and pushed back again by their springs, after the dirt particle is gone), they do not have a perfectly snug fit but rather a tiny bit of sideplay within the holders. The friction between brush surface and commutator strips cause the brushes to lean in their holders a fraction of a degree, since the friction pulls them to one side. The brushes wear in this oneside leaning position, which is not perfectly symmetrical. When the motor is reversed, the drag of the friction is pointed in opposite direction and makes the brushes lean against the other side of the holder. For a short while, this sharp brush edge is the only electrical contact with the commutator copper, which is too small for the designed current flow. Hence the sparking, which lasts until the sharp edge is worn down and the brush again makes full contact with the copper in its other leaning position.

This is not only true in power tools, it even happens in very large brush type motors. The pic below shows a French built locomotive as used by the Moroccan Railway. We also have these locomotives in Holland, that uses a DC catenary grid (1500 Volts). Holland has many trajects with train stock travelling back and forth between terminals some hundred miles apart, all day. Many of our trains have a steering cab at one and a locomotive at the other end. At a terminal the driver just switches the cab for the train to make a return journey, so the locomotive alternately pushes and pulls when it travels back and forth. I chose this pic because the locomotive is shown with its upper bodywork pulled up, offering a rare view of the bogies with their large single traction motors. Each motor is rated at nearly 3000 HP and is 1.30 metres in diameter. It has 8 poles, so the field has 8 stator coil groups and the armature is fed by 8 sets of carbon brushes. In each set there are two brushes of 7 cms width side by side, to provide a contact track wide enough to manage the 3500 plus Amps flowing through them. When these motors have run for some time, they produce little sound, only the fans and gears are discernable. But when the train leaves for its return journey, you can clearly hear the commutator strips running beneath the sharp brush edges, when the armature runs in reverse and the brushes are pushed against the other side of the holders. This goes on for some minutes, after that the motors are nearly silent again. I've seen such a motor on a test bench in Alsthom (manufacturer) video footage, there is some sparking involved, most of which is gone again after a few minutes.

The sparking in your picture will not go away however, this motor can only run one way!

greetings

gerhard

[mikm]

My thanks to all (especially gerhard for your insightful comments) for an interesting thread. Nice work.

[GraemeCook]

Hey Batpig

Gerhard's quite correct. Put a locomotive motor in your sander and it will reverse very well.

Cheers Graeme

[Knurl]

Thanks Bob. I must try that too. I'll bet I can clean the belt better if it's reversed.

BTW all my belts have a diagonal join so reversing them can't possible make any difference.

[Fossil]

So he can back it over the line at the Belt Sander Drag Races? When I was working in a large joinery shop in the seventies, I got my first promotion and significant pay rise due to belt sander racing. Long story. :)

[gerhard]

I never used sanding belts mounted against arrow direction myself, but i think there is little harm or risk involved when doing so. There is also some sense in the claim that the "shadow sides" of the abrasive particles that have not yet be blunted down, offer some additional belt life when the belt is used in reverse after it has been worn down in normal running direction.

Like a drive belt, a sanding belt is subjected to a large amount of pull and friction and its material changes thousands of times between a bent shape (when it is guided around the rollers) and a flat stretched shape (when it runs the distance between the rollers). The glued joint is the most vulnerable for these continuous shape changes and will "fatigue" earlier than the plain single layered linen in the rest of the belt. I've never experienced torn or ripped belts but i've experienced several used belts of which the glued joint snapped loose all of a sudden. A snapped belt is not much of a risk, suddenly you're stuck with loose ends and the machine just sits there running idle, that's about all.

The risk of glue joint failure in a reverse mounted belt is more on the outside than the inside. At nominal load and with regular cleaning, there will be more than enough grip for the rubber coated drive roller on the inside of the belt linen. Only during very heavy load or with soiled surfaces (dust between belt and roller), slippage can occur. In that case the rubber has a peeling effect on the joint, which slowly starts to fray at its edge. But since the rubber roll is smooth without any profile, it will take a long time for the entire glued joint to be peeled off and fail for only this reason.
The risk is higher on the outside, since the materials that are sanded down, are on average rougher or coarser than the rubber drive roll. With a belt running in reverse, the formerly trailing outside joint edge now becomes a leading edge in running direction. With a properly mounted belt and the outside joint edge in trailing direction, nail heads and such stand a good chance to be (inadvertantly) sanded down together with their surroundings without any problems; there is more risk of the dust bag catching fire because of sparks then of the belt being torn. But with a leading joint edge colliding with protruding bits, there is a chance of snagging, which may peel or tear the glue joint. The belt material itself is tough and it takes a lot to tear it, it's most often the glued part that gives.

The joint is cut and glued in a diagonal instead of straight fashion, to better spread the load of pull and shock forces over the entire joint width. When the joint reaches the point in which it is pulled between the machine's sole plate and the sanded material, it would experience a very sudden increase of friction and pull load on it, when it was cut in a straight fashion. The same effect goes for electric planer blades, that collide "head-on" full width with the material at every revolution. The Festo HL850E planer has one single diagonally mounted blade in its drum and is as such fairly unique. This machine is renowned for operating more silently and having less blade wear and smoother cutting efffect, proving that spreading the load through diagonal design indeed makes sense.

greetings

gerhard

[gerhard]

Haha, Fossil, i can picture it, many years ago together with some mates i also tried out how fast these things would go on a hall floor. Secure the switch in on-position, fit an extension cord, plug it in and watch it run. Most belt sanders manage about 350 metres per second no-load, that's about 14 miles per hour. The fastest was a Mafell model that managed 450 m/sec, that's approx. 18 mph. That's not much compared to radio controlled model cars, but the sanders beat the socks of those when climbing ramps! They're very good at that, since they have plenty of caterpillar-like traction. The Metabo 4350 has a sliding strip on which part of its weight rests. As expected, it kept spinning in circles and was useless in a contest.

[Batpig]

Dear Lads,


That pic shows how all my ozitos have worked straight out of the box.
That is so funny! :U You're one unlucky Ozitoer...:; I've actually had pretty good luck with them so far - especially the little Rotary Tool and the legendary Rotary Hammer. You know, yesterday afternoon I nearly bought their top-of-the-range Orbital Sander (as in the good-old rectangular sort) to solve the little Skirting problem in question, but I ended up going for that $99 1/3rd sheet Makita BO3700SP that's currently doing the rounds instead, because it fitted onto my Dust Extractor straight out of the box (It had absolutely nothing to do with how good it might look sitting in my "sanding" box next to my BO5021 Random Orbital, I swear...:no:). Anyhow - made in China, but a very nice little machine nonetheless. And a better "fit" when sanding the 65mm high Skirting than the bigger 1/2 sheet Ozito...)

The reason everyone is saying not to do this is because you will tear a gapping big hole in the fabric of time.
Hang on! I'll see if it's got a "Made in Hadron, Switzerland" sticker on the side...:wink:


My advice is instead of going left to right all the time, try pointing the thing in the other direction.
Aahhh.... Altogether too simple, my Good Man :doh: (and anyway, in the other direction, the cotton-pickin' Drive-Belt Cover stops you from getting the Sanding-Belt all the way down to the bottom of the Skirting Board - which is only 5mm or so above the floor...)


Gerhard's quite correct. Put a locomotive motor in your sander and it will reverse very well.
You know, the one out of my Hornby might actually fit, too! :p


When I was working in a large joinery shop in the seventies, I got my first promotion and significant pay rise due to belt sander racing. Long story. :)
Fancy that - they've been racing the darn things since way back then :? (and I'm assuming that it was here in Australia, too...) What brand used to win back then - Sher or Elu?...:q

Gerhard - you are the "Bradman" of PowerTool Posts. Thanks for the great replies...

Best Wishes,
Batpig.

[gerhard]

The current hi-potential in a belt sander contest could be the Makita 9403 : 500 metres per minute!

[rrobor]

I dont believe that, even if your extention lead was that long, you couldnt run fast enough to to feed it out :doh:

[gerhard]

Indeed you can't keep up with the things and with a 30 metre lawn mower extension cord the fun only lasts seconds, because- apart from the cord- few wide halls with smooth floors are longer than that. Wide halls because a collision equals an expensive repair.

But it is true nonetheless, we tried it and raced them! Don't imagine something on a grand scale though, it was just a bit of pranking around in the timber storage hall of a furniture factory. Far from a happening on a real circuit with a trophy and champagne at the finish, just a few mates at the start and some more at the end of the hall to watch which machine arrived first. Seeing is believing, it was fun! Modern radio controlled model cars (even the electric ones with NiMH batteries) are known to reach speeds beyond 30 mph, so they outclass the belt sanders.

[gerhard]

To give you an impression: this is how we did it. There is no need to feed the cord by hand, it is unrolled neatly by the sander itself when it is first coiled with care on a broomstick, with non-overlapping loops. You can see how well this unwinding can work in the James Bond movie "For Your Eyes Only", where James Bond and Melina Havelock are bound together to be pulled underwater on a rope tugged by the boat of bad guy Kristatos.

As neatly as the rope unwinds in the movie, so does the extension cord. At the end of its tether, the sander automatically unplugs itself and comes to a standstill. No harm done.