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Some help would be appreciated [Jan. 14th, 2009|12:49 pm]
gadget_design

gadget_design

[log_junkie]
So here's what I'm trying to do:

I purchased a Hamilton Beach single-serving blender (Model 51101) for a chemistry experiment I want to run. I'm slightly modifying it for better control over reaction conditions, but that's not my main concern. My reaction time is 2 hours, and I don't know if the blender motor can handle two hours of continual use. Customer service said no, but I think they're supposed to say that, and I doubt the lady I talked to knew anything substantial about motors.

Second opinions on motor durability? I'm not concerned about warranty/long-term use. Any advice or directing me to someone who would know a good answer to this would be appreciated.

Thanks!
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Comments:
[User Picture]From: pfcblogshere
2009-01-14 09:35 pm (UTC)
I think you'll be fine so long as whatever you're blending isn't stressing the motor. You're probably not dealing with something highly viscous or with chunky particulates floating around. While you're modifying it you could cut / drill holes around the base to give more airflow around the motor, and maybe pull out the thermal cutoff if there is one.

Blenders tend to spin pretty fast. I wouldn't be surprised if it starts acting somewhat like a centrifuge after a few minutes and that might not be appropriate. It's also likely to fold a lot of air into your mixture. Both problems could be reduced if you went to your local hardware store and bought a dimmer (probably has to be a fan dimmer at 175W, not a light dimmer) to wire into the circuit for speed control.
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[User Picture]From: log_junkie
2009-01-15 12:07 am (UTC)
Hey thanks! That helps a lot.
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[User Picture]From: _duncan
2009-01-17 11:12 pm (UTC)
A "router speed control" from Harbor Freight ($16-ish regularly, $10 on sale) is a good choice for adjusting the speed of a compatible motor. I use one to make the fireplace blower quieter during holiday gatherings and another to make the coffee maker a bit less enthusiastic.

http://www.harborfreightusa.com/usa/itemdisplay/displayItem.do?itemid=43060
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=43060

For part of its range the speed control reacts to changes in load with positive changes in duty cycle. This makes stalls less likely than with a standard lamp dimmer.
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From: hattifattener
2009-01-15 08:17 am (UTC)
It likely has a (non-resettable) thermal fuse built into the motor windings, so if you do overheat it, it'll just stop working rather than catching fire. So that's good.

The motor will be a reactive load, which is another reason not to use a lamp dimmer, plus what pfcblogshere says.
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[User Picture]From: log_junkie
2009-01-29 07:26 pm (UTC)
here's what customer service sent me in an email:

Thanks for contacting us.

You don't' need to run the blender no longer than 1 minute at a time.


Thank you for contacting Hamilton Beach Brands and please let us know if there is anything else we can assist you with.


Catherine
Consumer Affairs
---

It made me lol. It just goes to show you how helpful customer service is.
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[User Picture]From: mightywombat
2009-02-23 02:05 pm (UTC)
I think it's pretty likely that your motor will heat up if you run it at length. You could try running the power through a dimmer or speed control circuit, but if you find that it is still heating up try taking the case off and turning a fan or air jet on it. Any component that passes a lot of current with any sort of resistance will heat up - it's just Watt's Law at work. Chances are that motor is passing a lot of current, since that's what gives it its speed and torque.
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[User Picture]From: log_junkie
2009-02-23 04:33 pm (UTC)
I'd be using it in a fume hood, which doesn't have exactly the same effect of putting a fan on it, but there's good air circulation (the fume hood sucks up toxic fumes away from the work bench).

Also, would something like this be good to use as a "dimmer"? We use the Variac to control the temperature of our heating mantles and in my head all it does is control the amount of electricity that reaches it. But I'm not an electrical engineer, so I could be wrong.

Thanks for your imput, it's really helpful!
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[User Picture]From: mightywombat
2009-02-23 06:20 pm (UTC)
Your Variac should do the job, since it's varying the voltage to the device. Varying the current to the device is harder to do and would just make something else heat up instead. Watt's Law calculates the power dissipated in a circuit - usually as heat - using the equation P=VI, where V is voltage and I is amperage, so you can see how lowering the voltage would probably solve the heat problem. lowering the voltage should also slow down the motor. I would still take the housing off and check that the temperature of the motor isn't getting too high. The heat generated by the current flowing through the copper windings of the motor can melt insulation causing a short.
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