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New Shopsmith DC-6000 Dust Collector

DLB

I believe the reason that the new motor housing reflects so much post-fab machining and the reason that mine and ssuel's have a different shape occurred to me this morning. It is clear to me, a near-certainty, that the new motor housing is hand made from a DC-3300 motor housing:

Motor Housings 1 2.JPG

Motor Housings 2 2.JPG

Essentially the DC-3300 fan housing and motor mating surfaces are cut away. The strange dip I noted at the top of both mine and ssuel's is where part of the air duct is cut away. And in my case these changes were poorly executed. The mating surface on mine came into contact with the cutting tool during this operation and was seriously damaged.

Problem, IMO: I don't see how this can really seal on a "good" one either. There is differential air pressure between the large volume of the housing / hood / collection bag and the motor housing. It might be a fair seal, but I use a 1 micron hood for a reason. Once the stuff has been collected, I want it to stay collected.

David

RFGuy

Wow....I had assumed, erroneously I guess, that these were all new P/N's. I am really surprised if they are re-working existing housings and/or manufacturing new ones that they are then cutting down like this. Glad I didn't purchase one of these "upgrades".

DLB

In the spirit of Tool Review, I have two more comments (or observations or nitpicking) about the DC-6000:

1) We've discussed the foam rubber 'seal' at the top of the motor housing. There is also a thick foam rubber donut seal at the air inlet. It is thick because the air inlet is something near 1/2" smaller in OD than the DC-3300 was, and it sits in the same semi-circle support with a semi-circle clamp over the top. I don't like the thick foam rubber here for the same reasons as elsewhere plus it is load bearing. The weight of the motor and fan assemblies is fully supported by the "U" at the motor end and the lower semi-circle at the inlet end. So the foam is going to start more compressed underneath that weight and over time this will compress more. The foam at the top will be more expanded. If the material degrades over time this will create a significant leak between the high and low pressure volumes. I don't think the foam donut is a good choice over the long haul.

2) The exhaust port of the fan/impeller is much lower compared to DC-3300, I'd estimate around one foot lower. The DC-3300 exhaust port was higher than the top of the motor housing and on the DC-6000 it is lower than the bottom. IIUC the DC-3300 exhaust duct is also designed to slow the airflow down some while still in the duct but moving downward. Combined with the increased air flow, there is quite a bit of turbulence in there on the DC-6000 keeping more collected stuff in motion. This is more of an observation than an issue, unless your DC leaks like mine does. In which case it is this dust that is suspended in the internal turbulent airflow that is leaking out.

Neither of these, nor the reworked DC-3300 motor housing (done correctly) worry me too much. My two concerns are the leak exhibited by mine and what I consider an open question about cooling the motor.

- David

dusty

I don't understand all that you are saying so I guess I am going to have to disassemble mine so that I can see for myself.

As for the motor housing - I took pictures of mine and while they appear to be similar I believe mine are not the same as yours. It will be necessary to dismantle for a closer examination. I won't be able to do that before next week but I will soon.

If In recall all past conversations about the DC-3300 conversion, I believe we were led to believe that the motor housing AND the impeller housing were new design and that they were metal rather than a composite material.

DLB

dusty wrote I don't understand all that you are saying so I guess I am going to have to disassemble mine so that I can for myself.

If yours is leaking similar to mine you'll probably see a bit of sawdust buildup on the grate on the main housing that covers the motor (where the wires come out of the main housing) and on the ground below it. The amount of sawdust leaking increases when more ports are open. It is not necessary to be making/collecting sawdust for this to occur, it is distributing already collected sawdust. So it is only necessary to have some sawdust in the bag.

- David

dusty

I dismantled my DC-3300 when I ordered the DC-6000. I have not used it since. Next week I will be able to get out to the shop to make some saw dust and I'll test it then.

When I dismantled, I did have a small amount of saw dust in the exhaust port but it was very little. What I am unable to envision is how saw dust from the bag gets up to the exhaust port. Is the back side of the motor housing (where the motor mounts) not a closed chamber?

DLB

dusty wrote ...What I am unable to envision is how saw dust from the bag gets up to the exhaust port. Is the back side of the motor housing (where the motor mounts) not a closed chamber?

Unlike the DC-3300, on the DC-6000 the motor mounts to the fan housing not the motor housing. The DC-6000 motor housing has both ends open. One end then becomes closed (-ish, IMO) when it mates to the fan housing. (See pics above, the DC-6000 motor housing is the darker gray.) That is where I think mine leaks, the 'flat' mating surface between it and the fan housing. I don't think it leaks around the motor mount because it has a rubber gasket/seal there, and the pressure differential is the other direction. I think the foam rubber "short seal" just above that grate on the inside is also possible. If/when I put it back together I'll seal one of these to isolate.

Note - when I removed the motor housing there was quite a bit of sawdust trapped between it and the fan housing in that flat mating surface. I did not remove the motor, just slid the motor housing off. I think this tends to support my theory that there was airflow between the surfaces.

- David

dusty

That just may explain it all. I was unaware that in the DC-6000 the motor mounts to the Fan Housing. This being the case, I might not tear into mine again. I will have to look through the pictures that I do have to learn why I did not notice something so significant. I did not totally dismantle the DC-6000 before installing it.

RFGuy

Dusty,

Did you take any airflow measurements yet?

DLB

Trimming the protruding screw flush reduced the gap between the top of the motor housing and the main housing from a ridiculous ₅/16" to a disappointing ₇/32". Looking down through the top gap I can see that the gap at the bottom is now closed. This was not a surprise, I knew the screw did not protrude far enough to be solely responsible.

Top Motor Seal.JPG

David

dusty

RFGuy wrote Dusty,

Did you take any airflow measurements yet?

No, I have not. For reasons I cannot control, I have spent very little time in the shop since I bought the conversion kit.

Furthermore, I am seriously considering a dismantle. I want to look closely at all of the mating surfaces that could become air leaks.

DLB

I ran a thermal monitoring evaluation on the DC-6000 yesterday. I didn't take pics of how I placed two uncalibrated thermocouples, I'll try to remember to get those as I remove them. Both are near top of the motor, attached with plumbing insulating tape (low R value), one nearer the impeller and one nearer the cooling fan. I reached a level of discomfort and stopped the test when one of the temperatures reached 235F at 70 minutes. The data shows the temperature was leveling off, but that is pretty darn hot. I don't know if the motor is thermally protected or what its max case temp is, I posted a pic of the data label earlier in this thread.

I did find data to support the following: Most motors are rated for a 40C ambient and Class B insulation (which was on the data label) is good for a 80C increase. This means a max temp of 120C (248F) at the windings. I'm not measuring at the windings, nor with only two data points, am I likely measuring the highest case temp. IMO this confirms my opinion that 235F was very hot.

Note: during my eval from about the 15 minute point the temp nearer to the cooling fan and nearer to the main housing grate was the higher of the two. The difference between them increased with time/temp, ending with a +10F difference.

Before removing the thermocouples I'm planning to run the motor/impeller in free air with no motor housing. My thinking is this will help to validate the above observations and any conclusions drawn from them.

- David

DLB

After three (might have been four) install/remove cycles trying to isolate the air leak my seals are shot so I've stopped working on this. These are items 19A Motor Seal (three sides) and 19B Short Seal (the thick one for the fourth side) that seal the open end of the motor housing to the main housing. My last evaluation was to tape up the perimeter of the motor housing to fan housing interface with duct tape and this significantly reduced the magnitude of the leak, I estimate 95%. Since both seals were probably damaged on the last installation I think that is acceptable. Whenever I do a final installation I plan to provide more robust sealing for the motor housing at both the main housing and fan housing interfaces.

So far I don't seem to have successfully communicated the problem to Shopsmith. I did get a response yesterday but they seem to feel that the primary problem is the large gap where the Short Seal goes and suggested that I could double up that seal. I think that is a problem but not the primary problem in my case. I still have a bad motor housing.

- David

dusty

DLB wrote After three (might have been four) install/remove cycles trying to isolate the air leak my seals are shot so I've stopped working on this. These are items 19A Motor Seal (three sides) and 19B Short Seal (the thick one for the fourth side) that seal the open end of the motor housing to the main housing. My last evaluation was to tape up the perimeter of the motor housing to fan housing interface with duct tape and this significantly reduced the magnitude of the leak, I estimate 95%. Since both seals were probably damaged on the last installation I think that is acceptable. Whenever I do a final installation I plan to provide more robust sealing for the motor housing at both the main housing and fan housing interfaces.

So far I don't seem to have successfully communicated the problem to Shopsmith. I did get a response yesterday but they seem to feel that the primary problem is the large gap where the Short Seal goes and suggested that I could double up that seal. I think that is a problem but not the primary problem in my case. I still have a bad motor housing.

- David

Seals are inadequate here too. I've been debating what to seal with. I'm thinking about packing cotton

rope in the gaps.

DLB

dusty wrote Seals are inadequate here too. I've been debating what to seal with. I'm thinking about packing cotton

rope in the gaps.

I suggest checking for that protruding screw first thing. Trimming it won't close that top gap, but might shrink it down to a more manageable size. I included a pic a couple of posts back.

- David

JPG

Poke a clearance hole for the screw?

dusty

DLB wrote
dusty wrote
Seals are inadequate here too. I've been debating what to seal with. I'm thinking about packing cotton

rope in the gaps.

I suggest checking for that protruding screw first thing. Trimming it won't close that top gap, but might shrink it down to a more manageable size. I included a pic a couple of posts back.

David

Do you know what the screw is for. I suspect it might be the spring steel clip that holds the dust collection bag. I have the clips but no screws that protrude into the inside.

I opened mine back up this morning and I now seriously suspect that I have air leaks as bad as yours.

I am unable to close a gap between the Motor Housing and the inside will the the dust collector. I am thinking that this gap is the result of improper assembly as much as inadequate sealing.

I also wonder if it would not be better if the 4" union was installed after the DC is set in place. Doing this would allow the union to be installed into and remain in the opening.

DLB

dusty wrote Do you know what the screw is for. I suspect it might be the spring steel clip that holds the dust collection bag. I have the clips but no screws that protrude into the inside.

Yes, for the clips on mine.

I opened mine back up this morning and I now seriously suspect that I have air leaks as bad as yours.

I am unable to close a gap between the Motor Housing and the inside will the the dust collector. I am thinking that this gap is the result of improper assembly as much as inadequate sealing.

There ought to be a "Short Seal" in that gap. Foam rubber with an adhesive surface.(?) It's not present in your pic. Do you have that?

I also wonder if it would not be better if the 4" union was installed after the DC is set in place. Doing this would allow the union to be installed into and remain in the opening.

Yeah, it's not a great fit. I'm kind of ignoring this part for now, plan to seal it up when I believe I'm putting the thing together for the last time. I think this is leaking back into the input, maybe losing some CFM but not losing dust back into the shop on mine.

- David

dusty

I have the "short seal" if it will reattach. If not that stuff is available in many different forms.

For the leak (gaping hole" across the top of the motor box, I going to trim some flashing to fit the contour and attach it with double sided rubber window/door tape. It works wonders around window casings - why not here. I am contemplating how I might use the same stuff all the way around the motor housing.

Notice the rope I wrapped around the fan housing. Makes a great handle for pulling this out and putting it back.

I have put it all back together twice and had to pull it out because the power cord was being struck by the motor fan. I had pulled too hard on the two cables when I put it together. That won't be a problem any more. I scrapped the plastic wire clip and put in one that grip the cable so that I can not pull it too far. Whyp pull it at all - because it is barely long enough to reach the power receptacle. Instructions warn about pulling too hard but if the power cord was three inches longer there would be no need to pull.

I do have the interfering screw that you mentioned (I denied having). I just backed it out some and will screw it back in when done with the assembly.

I'm also pondering a slightly longer 4" union so that I can install it from the outside after the DC is dropped into place. The controlling factor will be if that is standard size (4"ID). The piece that came with the kit will slide through the hole in the main housing.

I wonder if these get any sort of production test???

RFGuy

IF you guys ever turn these dust generators into dust collectors, it would be nice if maybe you created a new thread with all of the details, including pics, of how you were able to seal up your DC-3300/DC-4650*. I am sure many owners would like to know best practices for how to seal their leaking DC-3300's so a tutorial thread would be helpful (IMHO). I did some work on my DC-3300 in the past, but I don't how well I sealed it up before banishing it to the attic. I am sure it still needed more work to seal it fully. However, my ShopVac™ dust collection system needed some additional seal work using the air-sealing tape like I mentioned here (https://forum.shopsmith.com/viewtopic.php?p=287099#p287099). After switching to HEPA bags and HEPA cartridges this wasn't enough so I had to seal the canister to keep the dust inside. Fortunately I have meters for measuring dust particle counts in my shop and I used them to fine tune my ShopVac™ system. Unfortunately I didn't have them when I was trying to seal my DC-3300.

P.S. I coined the DC-4650 name to apply to these upgraded DC-3300's since they are halfway between a DC-3300 and a DC-6000. ;)

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