PowerPro Thermal Performance

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DLB
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PowerPro Thermal Performance

Post by DLB »

In a recent Woodshop Nerdery Video, Tom mentions receiving an Inverter Heat warning on his new Mark 7. https://www.youtube.com/watch?v=raIN89AvJvs starting around the 6:00 mark. He reports that he was planing using a Mark-mounted Planer for about an hour when this occurred. I was/am surprised at his report. While I knew that PowerPros would heat up quickly at high RPM, I would not have expected this at Planer speeds. I recalled some details of a planing test that SS had done and I found this reference to it:

"...The most notable of these tests involved a punishing trial of the machine's ability to keep performing during a grueling thickness planing study. We started with a sizable stack of 8-foot long by 2" thick by 6" to 8" wide white oak boards.

We set our Mark V-powered Shopsmith Thickness planer for the fastest feed rate and a 3/64" depth-of-cut... then started feeding our boards through the planer. We continued this process over several weeks in one-hour increments without stopping until we had fed a mile of white oak through our planer... with no bogging, no complaining and no overheating !...
" (https://www.shopsmith.com/shopsmithpowe ... nology.htm)

I have to say, I am seeing that report in a different light after watching Tom's video! I'm kind curious to know what the phrase 'without stopping' means in this context... While a 'mile of white oak' sounds like a lot (especially at today's prices) at 'fastest feed rate' of 12 fpm it comes to 440 minutes of actual planing. That's a lot of planing, but it is not a lot of 'one-hour increments' 'over several weeks.'

- David
RFGuy
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Re: PowerPro Thermal Performance

Post by RFGuy »

DLB wrote: Mon Sep 05, 2022 10:03 am In a recent Woodshop Nerdery Video, Tom mentions receiving an Inverter Heat warning on his new Mark 7. He reports that he was planing using a Mark-mounted Planer for about an hour when this occurred.
:eek:
In fairness what hobbyist ever planes for an hour straight? The Mark V is NOT a production machine even though they charge production machine prices for it now. Also, given the very well documented history of PowerPro heat issues (at high speed) since its inception, I can't understand why anyone would leave a PowerPro running for an hour straight with no breaks. JMO. Continually seeing these kinds of issues come up for the PowerPro AND the fact that Shopsmith never seems to address them to the Shopsmith community at large is why I will never own a PowerPro.
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bainin
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Re: PowerPro Thermal Performance

Post by bainin »

I dont have the planar- have a separate box planer...but I have run in overhead routing mode (9500 rpm) for couple hours at a time without running into the thermal error above. My PP is the DIY version.

Definitely the case gets quite hot to the touch.

My general assumption is that most of this heat is generated by the V-belts and their tensioning.

b
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BuckeyeDennis
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Re: PowerPro Thermal Performance

Post by BuckeyeDennis »

I'd be curious to know if Shopsmith did those planing tests while plugged into 240V. This is a use case where that could make a difference.
RFGuy
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Re: PowerPro Thermal Performance

Post by RFGuy »

There is also no mention of shop environment used for either testing. Shopsmith could have performed their test in winter with no heat on....and Tom could have done his tests in his garage in the summer with no AC. Shop ambient temps could be a factor as well.
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RFGuy
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Re: PowerPro Thermal Performance

Post by RFGuy »

Ok...after noodling on this some more and searching the forum, I came across a post that confirms what bainin suggested. The same "inverter overheat" message on the PowerPro was reported by a forum user four years ago and the link is below (also re-posted inline for anyone too lazy to click the link). I initially thought this was just an electronics self heating issue when I first read this thread because it mentioned the inverter, but in actuality, I think, the ambient air inside the headstock (for Tom) is getting too high leading to the power FET's and related electronics getting too high in temp so the temp sensor is catching this and reporting it on the LCD. Also matches my limited overheat experience on a non-PowerPro headstock. I don't do extended planing sessions but the longer sessions for me on my Mark V are woodturning. Once or twice I have overtightened my belts and observed the outside of the headstock getting too hot for my tastes so I backed the belt tension back down. I suspect Tom has belts that are too tight on his PowerPro leading to this issue and/or he did it in a hot garage.

viewtopic.php?p=251427#p251427
rat1932 wrote: Sat Aug 25, 2018 4:27 pm I had bearing knock and heating.

The heating was measured with an IR thermometer at various places around the headstock with the cover removed so as to get access to the belts and bearings on the left side. The upper belt was running above 180 degrees and the motor belt was runnig about 140 degrees after about 30 minutes of running. This is without even a saw blade attached. The tension on the belts were equalized as specified in the instructions.

I had bearing knock even when I turned the quil by hand in the direction the blade would turn. Turning the quill in the reverse direction produced no bearing knock.

The high heat from the belts and the knock sound made me suspect the belt tension was too high. I adjusted the idler shaft so the short belt had less tension (a very slight give when pressed) and adjusted the motor so it's belt had a slight give when pressed. Then I equilized the tension on both belts as described.

The bearing knock when turning the quill by hand was gone. After running for 30 minutes produced a belt temperature of less than 140 degrees.

I have not done any sawing yet, don't know if I will get belt slippage but when the belt equilizing was done, the machine was as quiet as it has
ever been and the headstock temp was good. I won't know how good until I run an afternoon session with the plainer, which produced the "inverter overheat" message that started this quest origionly.

Bob
rat1932 wrote: Tue Aug 28, 2018 5:25 pm After thinking about what I had done in adjusting the belts, I wondered if I had considered or even knew everything that was necessary to set up the belt tension to reduce internal heat.

In the 'Checking Belt Tension' section of the Mark V Manual it instructs: 'To check the belt tension of the poly V-belt that connects the idler and the drive shafts , remove the belt cover from the headstock. With your fingers, lightly push in on the poly V-belt. If you can push the belt in more more than ¼ inch when applying light pressure, it may need to be retensioned.' I know that SS has changed the part number on the upper belt for the PP but I can't tell if it is the same belt.

The upper belt on my PP headstock was so tight that no deflection took place when I pushed on it. It smelled hot, in fact, the belt temperature was above 180 degrees after 30 minutes of run time without even a saw blade connected (belt cover removed).

I decided to ease the tension on the upper belt. I adjusted the belt tension by adjusting the eccentric on the idler shaft to provide 1/8 inch deflection when pushing on the belt, then clamped the eccentric bushing so that adjusting the motor belt would not change the upper belt tension.

I adjusted the motor belt for approximately the same deflection as the upper belt and adjusted the angle of the motor pulley to align it's plane of rotation with the top of the motor belt as it goes around the idler shaft. I also checked that there was no offset in the grooves of the belts as they ran around their pulleys (in other words, the belts would not approach or leave their shaft pulleys at any change in angle). I then adjusted the eccentric to equalize the tension on both belts.

As a result, the temperature of the upper belt after 30 minutes of runtime has gone from above 180 to 122 degrees. The motor belt has gone from 140 degrees to 119 degrees, the upper bearing was 145 degrees to 99 degrees, and the electronics box was 96 degrees. The ambient temperature in the shop was approximately 72 degrees.

I will monitor the temperature with the headstock buttoned up, but then I will not be able to measure the belt temperatures directly. The only significant point will be the top left corner of the headstock.

The next problem will be solving added cooling for those times when it is needed. My current thoughts are: use a filter canister from a shop vacuum to filter the air, a 12 volt fan, size to be determined, as a standalone assembly and tubing from this assembly to the inspection port on the back of the headstock. Fan power will come from a 12v AC to DC converter rated at 0.5a or better or if you have a small AC motor driven fan you don't need a converter. I have given up installing this assembly on the back of the headstock because of interference that it presents with operations unimageable at this time. This is still a design in progress.

Bob
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edma194
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Re: PowerPro Thermal Performance

Post by edma194 »

I'm not surprised to find out the PowerPro needs to adhere to a duty cycle, but their marketing and technical literature gives no indication of this. External cooling as suggested above should help. Small 12V boxer fans don't move a lot of air although wouldn't take up much space. AC versions are larger but move 10X the amount of air. The fans come in various sizes and would need filters that would reduce amount of air flow.

There aren't many places to locate a fan on the headstock. The inspection port is a good location, not a very large opening though, and if it sticks out the back it could interfere with using a quill handle on the back side. The left side nameplate is already a vent location, but a fan there might interfere with left side SPTs. My choice would be in the motor pan, it's an empty shell for the PowerPro and anything that will fit between the way tubes should work. A right angle connection pipe or hose may be needed to clear items stored below the bench tubes. It would have been nice to have an auxiliary AC outlet on the PowerPro so the fan would be on whenever the motor is running. Maybe there's some kind of device that would detect the heavier current used by the PowerPro in operation to activate a fan. Wherever it's located the large vent opening on the bottom of the motor pan may need to be closed up to keep the positive air plow through other openings.

Inexpensive 4" fan

More expensive 4" version

3" fan

I need a vent fan for another reason so I'm inclined to get one of those cheap ones and play around with with one installed in the bottom of a motor pan.
Ed from Rhode Island

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DLB
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Re: PowerPro Thermal Performance

Post by DLB »

edma194 wrote: Wed Sep 07, 2022 10:02 am I'm not surprised to find out the PowerPro needs to adhere to a duty cycle, but their marketing and technical literature gives no indication of this. External cooling as suggested above should help. Small 12V boxer fans don't move a lot of air although wouldn't take up much space. AC versions are larger but move 10X the amount of air. The fans come in various sizes and would need filters that would reduce amount of air flow...
Much good work has been done by other owners. My preference is a system with filtration and of sufficient air volume to slightly pressurize the headstock, thus also helping with problems reported to be caused by sawdust in the headstock.

I've also noted that the 'old motor' (probably the new one as well) has an effective fan. It is a fairly typical TEFC setup. What it lacks, IMO, is an effective design for the airflow. In operation, it seems to just recirculate air around inside the headstock. In operation, that air is getting hotter anytime the machine is running. There is no cold air inlet for the low pressure area at the center of the centrifugal fan, and no hot air exhaust. It is a leaky headstock, so of course it is not exactly an oven, but in contrast with the conventional headstock there is no defined inlet and no defined exhaust. It is my opinion that a filtered air inlet in the right location would be a vast improvement, no additional fan necessary. I completely agree that the motor pan is the place for it.

- David
RFGuy
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Re: PowerPro Thermal Performance

Post by RFGuy »

I still believe that the inverter overheat issue that Tom reported is likely an overly tight belt that is exacerbating the already overheated cavity of the PowerPro headstock. Bainin suggested this and I have observed the same problem myself with the standard headstock...also believe this has been mentioned before in other threads in the past about belt tension. When it comes to the solution that is really the key question I think. Active ventilation is definitely a solution but there are challenges as pointed out above. There are alternatives as well, e.g. given the compactness inside the PowerPro headstock it could lend itself to replacing the power supply module heatsink with a liquid cooled setup (like a gaming PC uses). Probably an external radiator makes the most sense and it could be mounted perhaps below the motor pan or on the back of the headstock. This would have the benefit of keeping the PowerPro headstock mostly sealed to keep out dust and avoid the sensor errors the PowerPro is prone to with dust infiltration. Of course, this is an overly complicated system to solve what inherently was a design problem to begin with. Also, if the coolant ever leaks and/or gets too low then the power supply will fry quickly so you always have to monitor the status of liquid cooled systems, i.e. they aren't idiot proof. The power supply module located above the motor was a bad design decision but of course was necessitated by the choice to make a PowerPro headstock that was a drop in replacement rather than building a brand new headstock entirely. Putting a switched power supply like this, which already has thermal challenges on its own, over top of the motor means all of that motor heat just rises right into the power supply module pushing it over its thermal limit under certain conditions. Another oddity with the PowerPro is the mostly sealed headstock with no internal fan to ventilate as David alludes to. Those heatsinks on the PowerPro motor and power supply module aren't very effective at cooling inside a closed cavity like that...nowhere for the heat to go and not enough air transfer across the radiator. Yes, some heat will exit through conduction in the motor mounts, etc. and some will radiate out from the headstock housing, but A LOT of it will be trapped unfortunately. Time for a redesign. I would be interested in PowerPro 2.0.
Last edited by RFGuy on Wed Sep 07, 2022 11:12 am, edited 2 times in total.
📶RF Guy

Mark V 520 (Bought New '98) | 4" jointer | 6" beltsander | 12" planer | bandsaw | router table | speed reducer | univ. tool rest
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edma194
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Re: PowerPro Thermal Performance

Post by edma194 »

DLB wrote: Wed Sep 07, 2022 10:29 am [Much good work has been done by other owners. My preference is a system with filtration and of sufficient air volume to slightly pressurize the headstock, thus also helping with problems reported to be caused by sawdust in the headstock.0
Keeping sawdust out of the headstock is worth having a filtered air supply by itself.
It is my opinion that a filtered air inlet in the right location would be a vast improvement, no additional fan necessary.
The right location might be different for conventional headstocks and the PowerPro. Without an additional fan besides the motor's a filter might block sufficient airflow for an inlet. I've dealt with cooling issues in electronic equipment over the years and getting passive airflow to hit the hot components can be quite difficult.

Another approach, simple but imperfect, would be fan blades that mounted on the auxiliary spindle. Remove the nameplate and provide a simple shroud and filter over the fan. A conventional motor would drive those fan blades at 3450RPM all the time. In a PowerPro the fan would run at motor speed, not all that effective at the lowest speeds, but maybe unnecessary at low speeds. Reverse might actually reverse airflow though. The shroud and filter should be easily removable to to take the fan blades off in that case.
Ed from Rhode Island

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