Thread: "Dolly" for an Angle Grinder?...

If its for a DIY project and not 'commercial' use, surely that photo gives you enough information to weld up your own dolly? For my own preference I'd go for a 3 wheeler and a front end adjuster for grinder height - but I'm clumsy at times.

Dear Bsrlee,

Thanks for the reply. In actual fact, I was going to (try to...) make one until I came across the one in the photo, which got me to thinking that where there's one, there could be others (that are hopefully cheaper by enough to make me not bother about making one...) I was just going to put a single somehow-adjustable castor-wheel under the Grinder's back handle, and bolt a handle bar setup (a bit like a Lawnmower's) into the side-holes for the Grinder's handle. If time permitted, I was going to rig up some sort of switch at the top of the handle too...

Anyway, I've still got a little time up my sleeve, so I'm still looking and thinking...

Best Wishes,
Batpig.

http://www.situp.com.au/ The sit up n Grind product seems pretty good if you listen to them. Shroud costs $230 by itself

Cheers Pulse

Dear Pulse,

Thanks very much for the reply. The "Situp" unit was in the back of my mind, but I was kind-of hoping for something more "walk-behind" in its arrangement. Boy - those cotton-pickin' Dust Shrouds sure are dear, hey! Tyrolit do one as well, and it's over $200 too...

Got a little time up my sleeve, so still looking at the various options...

Best Wishes,
Batpig.

Hi, Michael, how are you?

by coincidence i recently bought an Ackermann + Schmitt diamond cup grinder through Ebay Germany. It's a Flex LD2806C, the seller wouldn't send it so i went to Germany and collected it. It was as good as new and went for 200 Euros. Its retail price was around 900, so it still paid to make the trip and wrap a nice weekend around it (Kassel region, lovely countryside, good food and beer).

The machine has 2800 Watts input and 2000 Watts output and is the sturdy 80's Flex design which still uses a metal motor housing. After half an hour of grinding your arms think it weighs twice as much and after one hour it must be close to ten times. So my limbs immediately agreed with your idea, i've been thinking of such a solution as well.
There are several more options like the one in your attachment to be found on the web, but they all have pushbars, depriving you of a subtle feel of what goes on between the disc and the treated surface.

With a right sort and good quality diamond disc, the abrasive effect is amazing on anything but the hardest concrete. Just like with a belt sander, without steady progress and a good plan-parallel position of the tool and the workpiece, uneven treatment like hollows or grooves can happen soon and unexpectedly.

I was thinking about a sort of low slung frame on 4 wheels or castors, not much larger and wider as the angle grinder itself. The grinder unit is to be suspended and adjusted inside this frame with a three point construction. The two (front) fixing points are the side handle threads on either side of the gear case. The third (hind) point is a rubber coated clamp in which the hind grip is clamped without damaging it. For adjusting you put the wheeled frame on a thick glass plate and make sure that the disc touches the glass plate in a perfectly circular way. With the grinder held in this position, you tightened the three suspension points, fixing the grinder perfectly plan-parallel with the wheels. Then you just lift the adjusted and wheeled grinder from the glass plate and put it on the floor. The disc will now work at a perfectly set height, just like the knives of an electric wood planer are set against the trailing part of the sole as reference. Makita uses this principle in its little PC1100 "concrete planer" . This machine slides along on a stainless steel plate, which is the reference for the working depth of the disc in front. Metabo later copied this idea for its LF724S rotary paint stripper. Only "sliding" on concrete is relative, the Makita's plate eventually gets scratchy and sooner or later rather scrapes instead of slides along. But our little grinding frame rolls on wheels, which is so much nicer.

Personally i wouldn't mind crawling next to it, like a child does with a toy, so i doubt that i would use a pushbar. Without that, your eyes are close to the process (granted; your ears are too) and just one of your hands needs to push the machine along. The frame takes the machine's weight, but you still keep optimal control over what's going on. If extra pressure is needed, your hand is much subtler in the dosage than both hands would be behind a pushbar. When there is a lump, the machine will not grind it away in one go but will rather hobble over it. Which is no problem, you just keep hobbling to and fro and keep gnawing at the lump. When all wheel touch the floor again, the lump is gone in a perfectly flat and smooth way. The four wheels are your guarantee for good results, just like a sanding frame is for a belt sander.

Most grinder dollies do not have a hinged bar, so forward pressure is partly vectored down as increased pressure on the disc, which to me seems to be no guarantee for all-over constant depth results. But i must admit i never used such an accessory, so my judgment is a guess and by no means an expertise.

I will make a drawing if this suggestion next week. By the way: still no German user's test reports on the Elektra Beckum table saws for me to translate and send to you. But i'll keep looking.

By the way, when comparing the LD2806C to its ordinary angle grinder sister L2806SC (which i also own and of which the diamond cup version was derived), i found little or no difference in its armature and field insulation grades. Neither has the LD-version a special flow pattern of the motor's cooling air flow or air intake filtering as compared to the standard L grinder model. So in essence both machines seemed to be very much the same, and the use of any ordinary grinder for this task would seem feasible. Until i saw the special dust seal unit underneath the arbour's bottom ball bearing collar! So with an ordinary grinder fitted with a diamond cup, you may be in for speedy bearing soiling and failure.


All the best and have a nice weekend!

gerhard

Mein leiber Kurator (aka Gerhard...)

Originally Posted by gerhard

...so it still paid to make the trip and wrap a nice weekend around it (Kassel region, lovely countryside, good food and beer).

Ahh - sounds just like what those Krafty Krauts had coming to them: another "Drive" through the Low Countries - except this time from West to East! I hope you caught them in a Pincer-movement... (Your description in brackets is even somewhat reminiscent of the way Guderian described a few of the localities back then in his memoirs...)

But a very nice "score" Gerhard - obviously German-made, and certainly better than my own efforts so far. Now here is a photo of my own humble 5" setup, which consists of a Bosch aftermarket-accessory Dust-Shroud that I have quite literally shoehorned (with the help of an Arc-Welder, some sheet-metal, and quite a bit of leverage...) onto the collar of a variable-speed 1200w 125mm GMC Angle Grinder. The GMC brand is (well, was - until it went broke...) sort-of like our equivalent of your "Einhell", but it has still managed to tackle everything in the way of concrete that I have thrown at it thus far. The modifications to the Shroud with the welder almost ended in disaster, because the Shroud itself is mainly made of plastic (which therefore started to melt...), but I managed to just "get over the line" in the end. The thing ended up as such a tight fit on to the Grinder, that I dare not take it back off now... (so I will have to buy another 125mm Grinder...)

Attachment 110375

For the sake of the unitiated readers, it is worth relating that the difference that a Dust-Shroud hooked up to a Dust-Extractor makes - when grinding concrete - must truly be experienced to be believed. Literally "Life and Death" in the long run, I should think. Anyway, as you can see from the photo above, the front of the Bosch Shroud is detachable, so that when it is removed you can grind very close along the side of walls. The next photo shows the Diamond-Cup wheel that I have fitted to this unit. I opted for a "Turbo" (sometimes called "Wave") style, due to its greater aggressiveness compared to the "Double Row" type:

Attachment 110376

This next photo shows where I presently am (so to speak) with regard to my large Concrete Grinding setup:

Attachment 110377

The parent Grinder is a 2200w 230mm Ozito (our new equivalent to "Einhell", since GMC is now "bust"...). Like most 9" Grinders, it is too powerful for anything much in the way of handheld work, so I hate it, and am desperately trying to kill it . So that's why the idea of grinding concrete with it makes so much sense. The blue-painted metal Dust Shroud that you can see on the beast is made by a New Zealand outfit called "Holer", which is marketed down here by Tyrolit. Their 7" Shroud with 73mm Collar was a perfect fit for the Ozito, but certainly not cheap at $195. The black strip on the floor next to the shroud is a velcroed-rubber "Skirt" that fits around the outside of the Shroud to form a seal with the floor to prevent dust escaping. As can be seen in the photo below, the Diamond Cup wheel that I have fitted to it is a 180mm "Wave". It is actually a "Husqvarna" product, but from their "Mizer" series. Nonetheless, the diamond-count looks pretty good compared to the generic-brand unit on my 5"er. As you may have also deduced, I haven't used the big Grinder in anger on concrete yet.

Attachment 110378

At this stage Gerhard, I was contemplating just doing something perhaps as simple as mounting a set of fabricated handlebars onto the sides of the unit, along with a height-adjustable castor-type wheel at the back, because the things really are quite stable on the concrete once they get going. With the metal Shroud and heavy Diamond Cup mounted, the big Grinder actually sits flat on the Diamond Cup wheel on the floor. But I certainly know what you mean when you talk about digging in like a Sander - the 5" did that to me a couple of times when I wasn't concentrating, so you might well be on to something when you talk about using a multiple-wheel "sanding-frame"-type concept.

Originally Posted by gerhard

So in essence both machines seemed to be very much the same, and the use of any ordinary grinder for this task would seem feasible. Until i saw the special dust seal unit underneath the arbour's bottom ball bearing collar! So with an ordinary grinder fitted with a diamond cup, you may be in for speedy bearing soiling and failure.

Oi oi oi.. (Fingers crossed!...)

I will post a photo if I manage to fabricate anything useful in the next few days.
Best Wishes Gerhard,
Batpig.

Hi Michael (and other members!)

Jeez, what a story, you've undertaken quite some experiments! Indeed the shrouds are quite expensive as loose accessories. Nothing compared with original brand quality diamond discs, though! The Original Flex brand version of the turbo disc (which they call "Thermojet") sets you back 500 Euros for the 180 mm version. The same amount buys you the entire 2800 Watt machine (including shroud) without such a disc!

I promised to make some sketches of the low-slung dolly idea with castors, which i had in mind. The frame contains an adjustable height clamp at the back, which fixes the hind handle of the grinder unit. As said in my earlier post, you place the frame with its wheels on a thick glass plate or some other smooth level surface (as an ideal adjustment reference) and just lay the grinder in it, resting on its disc and the frame's back handle clamp. Then you adjust the machine's tilt by rotating the knurled nuts, with which you can lift of lower the handle clamp through the piece of threaded rod, which is welded underneath the clamp. You adjust it in such a way that the grinding disc touches the surface full circle. Then you secure the clamp in its set position with the two knurled nuts, and fix the grinder's back handle with the top clamp part and two bolts with winged nuts. The grinder now already has the proper position and depth, only the two knobs that are screwed into the inside threaded side handle holes neeed to be tightened. When's that's done, there is your three point machine suspension, which is both sturdy and easy to set.

The second pic shows the contraption with the grinder unit fitted. When the grinder is adjusted and set, the complete unit is lifted from the glass plate and put on the concrete floor and is ready for action. To operate it, i would prefer to crawl beside it with earmuffs and knee cushoins, to be close to the grinding process. Using the motor housing as a grip to roll the thing around is already a satisfactory solution, since there is no weight to carry, just some guidance is necessary. This setup could be upgraded with a safety cut-out switch, a top handle grip and other handy details. A hinged push bar of a lawnmower type could also be added. A shockproof spotlight pointing at the area to be treated, could be another idea. I saw some electric wood planers once, with their own little retractable stand incorporated in their soles. After the stroke and having switched the thing off, you could make the stand stick out with a lever and immediately put the planer down on a surface, even with the blade drum still running. The stand partly lifted the sole from the ground and prevented the blades from touching it. I seem to recall that Bosch had some planer models with this feature. This idea could also be added to this contraption. E.g. two little spring loaded legs could lift the front castors from the ground while the machine is switched on. When the machine has reached full rpm and when the user has its hands in the right places to safely start work, a flick of a lever may pull in the legs and make the front castors and the disc touch the surface again.

Phantasy is limitless!

The LD2806C which i got through Ebay and which i used as an example here, is indeed a German product. The "Original Flex" firm from Stuttgart (formerly Ackermann + Schmitt) was the one that invented the angle grinder. A bit of history is to be found in this link:

http://www.flex-tools.com/gb/Unterne...n.php?navid=18

Greetings!

gerhard

Dear Gerhard,

Those sketches are excellent!... They're actually somewhat - dare I say... artistic...

Your choice of using Tubing for the frame instead of an open section (such as Angle) is quite interesting. I say this because with the type of frame you propose - where there is no cross-member joining the arms at the front - torsional twisting forces (imposed by the weight of the Grinder) present at least a theoretical load that should be considered. Some different detailing that allowed you to bolt the two arms tightly to the side of the Grinder (and therefore convert the Grinder into a stressed-cross-member) would most likely eliminate these torsional forces as being a design consideration, but all the same, it just so happens that gram-for-gram, Tubing (either square or circular) offers greater torsional-rigidity than any shape of open section, and is therefore the ideal choice of section for your frame in its current form. Coincidental? Or perhaps you have been technically trained?...

For my part, I was actually planning a two-castored Trolley, where both of the castors were at the back of the machine, so as to:
1) Allow the Diamond-Cup to always contact the floor
and,
2) Allow me to "slew" the whole contraption sideways somewhat, rather than just back and forth (as would be the limitation if the Trolley used wheels...)

But now, seeing your 4-castor design has got me thinking again. Are you in a rush? If not, perhaps you could wait a few days to see what I end up coming up with, which will hopefully be along the following lines:

In certain cases I think 4 castors would definitely be the best way to go, but I think the front two castors need to be mounted forward of the Diamond Cup, rather than behind it. This will allow the resulting setup to passively sniff out and grind any "High Spots" for you automatically - so to speak. I currently locate high spots with my collection of aluminium Plasterer's Straight-Edges that I use for cement-rendering, and I can assure you that it is a time-consuming pain in the posterior . But with the Diamond Cup hanging down midway between two sets of castors, the contraption would "bottom out" over any high spots, and hence grind them (and only them...) in the process - instead of possibly the whole floor. Then, when you have eliminated the High Spots and want to give the rest of the floor a perfunctory grind for the sake of completeness (and you therefore need to get down into the Low Spots as well), a 2-castor setup becomes preferable, in which case you could either:
1) Somehow detach the front two castors (The overhanging weight of the front half of the frame would probably enhance the grinding performance of the Cup)
or,
2) Possibly detach the whole front half of the frame, if your design enabled this... (this would allow you to get closer to walls in the fore-aft direction...)

If I am able to, I will try to go down to the local industrial area tomorrow and pick up some steel and castors, with the aim of butchering metal over the weekend...

And now a couple of photos that might come in handy for you if the time ever comes where you need to replace that unbelievably expensive Flex Thermojet disk. The first is of my 180mm Husqvarna "Mizer"-series disk, after we "broke it in" on Monday with about a solid half-hours worth of grinding:

Attachment 110938

This second photo is a close-up shot that gives you a better idea of the diamond-count of the disk, as well as an idea of the hardness of the metal medium in which the diamonds are embedded. The diamonds seem quite well exposed, meaning that the metal is not too hard. I hope on the other hand that it is not actually too soft. Excessively-hard metal medium can apparently lead to glazing and burnishing of the diamonds, by which they can lose their abrasiveness through not being exposed enough to wear away. Excessively soft metal can simply lead to premature depletion of the disk without full exploitation of each diamond's hardness. Anyhow, only time will tell the true story with the disk in the photo I guess...

Attachment 110939

Best Wishes Gerhard,
Batpig.

Originally Posted by Batpig

My Dear Fellows,

I wonder if any of you have ever come across a walk-behind "Dolly" (sort of like a Trolley...) which was designed to carry a large Angle Grinder with a Diamond-Cup Disk down at floor-level, for the purpose of grinding lumps out of concrete floors?...

If you're struggling to visualise the concept, this photo will doubtless explain it better:

Attachment 109441

Trouble is, the one in the photo costs over $600 - before you even add the Angle Grinder, Dust Shroud, and Diamond-Cup...

So, has anyone seen something similar, and hopefully cheaper?

Many Thanks,
Batpig

Hi Batpig,

I have seen many hits on my website regarding the Situp N Grind so although this subject is very old it still generates interest.

The Situp N Grind is my development after working on my knees with a grinder for a few years, it works really well and hundreds of contractors use it because nothing else works as good for anywhere near the price.

Obviously you guys would like a cheaper device, but the trolley idea will not work. I am temporarily stumped by this problem now as you can see by the announcement on my website Edge Grinder. After many trials with frames (dollys) and wheels I found that the grinder will only work if floated on the disc and the only way to do that is to sit above it and control it with handles at 90 degrees to each other or use it kneeling down.

I am currently trying to produce the Situp N Grind for much lower cost without sacrificing the performance, but as I said, dollys do not work very well.

The problem with frames and wheels is that if you suspend the grinder it will not cut into the floor, if you suspend it at one end only it will not cut flat and with both of those methods the setup is ruined every time the floor dips or raises. As you grind into a raised area the wheel bites in strongly which causes a very strong lateral force that can only be controlled if you are above it with one hand on a handle to the left side of the head which is how you grind by hand on your knees or sitting on a stool using Situp N Grind.

So to conclude I suggest that a dust shroud worked on your knees is the cheapest solution for grinding concrete floors. I estimate that about 27,000 of these shrouds are sold worldwide every year and I know that professional floor preparation guys buy most of these.

Peter.