Linear solenoid regulations?

[dardeshna]

Team 8 is hoping to use linear solenoids on its off season robot, but the regulations about linear solenoids are a bit vague. The stronghold manual states:

Electrical solenoid actuators, no greater than 1 in. stroke and rated electrical input power no greater than 10 watts (W) continuous duty at 12 volts (VDC)

http://www.mcmaster.com/#linear-solenoids/=147m049

We've looked at the options on McMaster, but are not sure how duty cycle and voltage factor into this.

For example: http://www.mcmaster.com/#69905k117/=147niam

If the linear solenoid has a 10% duty cycle, does that mean we can go with a higher wattage solenoid? What if the solenoid is used more than 10% of the time? 12v vs 24v?

Thanks!

[GeeTwo]

I don't recall seeing this particular question in the Q&A, but based on analogy from some pneumatics questions, the answer is most likely going to be that if a solenoid is only rated for intermittent use, the power at intermittent use is going to be the criterion, without adjustment. Clearly, if it is rated for 10W intermittent use, it is rated for no more than 10W continuous use (and probably considerably less). Only if a solenoid has ratings for both intermittent and continuous use will this distinction be helpful.

This is my opinion only, based on two years following the Q&As. If this question becomes more than academic, I recommend submitting it to the Q&A on FIRST as early as possible after it opens in January. Note that the solenoid limit rules changed recently, and are (in my estimation) roughly equally as likely to change in 2017 as to stay the same.

From a practical standpoint, you will also need to budget the solenoid current against whatever switching mechanism you use. In most cases, this will be higher than the FRC legal limits, but there have been a few cases where it was basically left to the teams to figure out that they had to watch out for blown fuses. Never assume that because something is legal it is also therefore practical.

[Al Skierkiewicz]

When this rule was written, the solenoid rating in watts determined the maximum current for any single operation. Duty cycle is not part of the rule. This was the solenoid used for the rule...
http://www.mcmaster.com/#69905k185/=148558h
This rule was written at a time when the GDC was putting limits on actuators as part of the engineering challenge. This part can be a good alternative for triggering latches, opening and closing small doors, etc. when a team has no other need for pneumatics.