RAS115 excessive heat

[BJM9818]

This past week we had to sand down a 10'x280' wood wall made most likely from Garapa or a ipe cousin.

What worked best was hitting it with 40 grit with the RAS then going back over with the 150 Rotex using 60 grit. 2 RAS and two Rotex 150's were used hooked up to vac's.

The RAS after a few minutes was almost to hot to hold. Even with gloves on my fingers were very uncomfortable with a few heat blisters. This was three consecutive  8-9 hour days.  I have used my Rotex's in abusive conditions most likely frowned on by Festool and it never  got anywhere near that hot.  I know hovering in the low 90's all week  didn't help. Anybody have this problem?  I also had an issue with the electronically controlled motor would disengage often requiring the tool to be turned off then restarted.

 

[AlexThePalex]

I know hovering in the low 90's all week  didn't help.

There's your problem. The RAS runs at 3800 RPM, unlike the Rotex which runs around 650 RPM.

A tool with a high RPM will produce more heat with its motor than a tool with a lower RPM and it needs to get rid of that heat to keep on functioning. But if the ambient temperature is in the 90's then you can forget about dissipating a sufficient amount of heat, and the tool will overheat untill the onboard electronics shut it off.

 

[peter halle]

A few years ago I was sanding a deck with my RAS and the temperature here (Richmond, VA) was similar to yours and with perhaps a little higher humidity and I was sweating so much that I was worrying about the damp sawdust extraction.  Yes my RAS got hotter than - but it rocked then and has continued.  Me,  I suffer more in this recent weather.

I usually gauge the heat effect by the number of shirts changed.  Many 5 shirt days in the past two weeks.

Peter

 

[BJM9818]

I understand a tool getting hot but it kept "disengaging the drive mechanism" after 20-45 seconds. It would spin but if I put it to the surface it would essentially stop.  I have used one of them to grind a ton of fiberglass and never had any issues but it definitely was cooler.

I can take the heat I just can't believe this sander is pretty much no good when used in temperatures exceeding 85 degrees.

Peter

Do yourself a favor and ditch the cotton shirts. You need to pick up some UA threadborne shirts. I was out there three of the four days with my guys and my shirt was dry and comfortable  as can be.

 

[peter halle]

I understand a tool getting hot but it kept "disengaging the drive mechanism" after 20-45 seconds. It would spin but if I put it to the surface it would essentially stop.  I have used one of them to grind a ton of fiberglass and never had any issues but it definitely was cooler.

I can take the heat I just can't believe this sander is pretty much no good when used in temperatures exceeding 85 degrees.

Peter

Do yourself a favor and ditch the cotton shirts. You need to pick up some UA threadborne shirts. I was out there three of the four days with my guys and my shirt was dry and comfortable  as can be.

Mine never disengaged.  Honestly I don't ever remembering reading about that.  Might want to try and call FESTOOL and ask about that.

Thanks for the advice on shirts!  [thumbs up] [thumbs up]

Peter

 

[BJM9818]

Both of them were doing it one is a year old the other 6+.

Shirts run $30 but worth not having something stuck to you all day long.

 

[nickao]

I understand a tool getting hot but it kept "disengaging the drive mechanism" after 20-45 seconds. It would spin but if I put it to the surface it would essentially stop.  I have used one of them to grind a ton of fiberglass and never had any issues but it definitely was cooler.

I can take the heat I just can't believe this sander is pretty much no good when used in temperatures exceeding 85 degrees.

I dont believe this is a heat issue, at least an issue where the ambient air temp is the cause.

My shop is far hotter, more like 103 and both Rotex and RAS are so hot gloves are needed to hold them. I used them for over 4 hours last night non stop with 24 to 80 grit grit hitting super hard exotics and neither acted weird other than being really hot. IMHO, 85 degrees is NOT hot enough as an ambient temp to effect these sanders. If 85 was the cut off temp we would have threads all over the place complaining of shut downs.

Even when it's 40 degrees I get these sanders so hot they are difficult to hold, from my perspective the ambient heat in the air has little effect on them. I never notice any difference in use whether it's 10 below or 103. Using them for hours on end with low grits has far more effect then the ambient air temp. The sanders get super hot no matter what my working conditions are, at least after the first 15 minutes of hard sanding or so.

This disengagement thing is weird to me, I dont think I ever read about it and after this many years  I would think there would be a thread somewhere on it(there may be).

Is it possible it's super humid and there is actually moisture in the units effecting the electronics? This could explain why two separate units were doing it for you, but they don't do it over in my shop. If heat was the sole cause of this I would think it would happen in my shop and fairly often. I don't sand super heavy like this once in awhile, my work entails using 24 to 36 grit Saphir on exotic woods for hours on end almost on a daily basis. I should be the first one to notice some weird heat related things going on. It's been really hot lately(I have been working nights to try to beat it), if something weird starts happening here I definitely will let you know.

 

[AlexThePalex]

The "disenganging"  - I have not had that with my RAS but I have had it with two DTS400 sanders that were broken because the motors overheated. When I turned them on their motor would look like it was running, became excessively hot, and when contacted with the material the pad would not move. After investigation I found the motor did not really spin, but vibrated in place. This happens when the field coil is burned. Both sanders felt and sounded like they were still running, but because vibrating is not the same as spinning, they had no power to move the pad when contacting the material. Their internal cooling fan also did not spin, so they heated up very quickly.

With your RAS, is there a situation where it returns to normal functioning, maybe like when it's cooler in the evening?

 

[BJM9818]

Alex

Yes the first few minutes they worked great. The disengaging I'm talking about is the pad would still spin when in the air but at a much lower rpm. If I were to try and make contact with the wood it would stop or almost stop.

If I kept the sander free spinning for 30 seconds or more you could hear the motor power back up and increase rpm. Sometimes turning it off for the same time would correct the issue. Once sanding again it would disengage after 30+ seconds. Made for a long day.

If I left the sander out in the sun for lunch it would have the same problem.  If I left it in the shade on concrete to cool after lunch it worked fine for a few min.

I would guess the temp around the head of the tool was 150 F or more. The air exiting the tool was hot enough to burn you with limited exposure.

Both Rotex 150's while hot powered through each 8 hour day without a hiccup. I own pretty close to one of everything festool sells in NA and I have to say the Rotex 150 was my first tool purchased and probably their best tool made.

 

[pingvinlakrits]

Hmm, my RAS115 got worked pretty hard on a floor renovation a few days back. It worked very well for two rooms but after two hours of pretty hardcore sanding/agressive removal it came to the point where it would disengage and spin down. After lifting it off the floor it would spin up again, slowly. It was quite hot to the touch but after a cup of coffee (cool down period) it was back in action. I thought it was some sort of overload protection though it was the first time I have encountered it.

Are you guys telling me I should be worried? It is still under warranty though.