REFLECTOR: speed brake ramblings

[michalk]

That's the exact setup I have too.  Simple is better.

Jim Sower wrote:
> I've already got a 3-pos UP-OFF-MomentaryDOWN switch for my belly 
> board.  All I need to do is beef it up a bit and I'll be there.  NO 
> extra wire, technology, transducers, failure modes.
> I like it simple ... Jim S.
> 
> michalk wrote:
> 
>> Right.
>> But in my last paragraph I addressed your point.  A DPDT switch would 
>> be needed, increasing the complexity.  The speedbrake system might 
>> behave something like this, using a DPDT switch, wired such that one 
>> end reversed the polarity:
>>
>> case1: 0 to 75lbf: switch is engaged such that correct polarity is 
>> applied.
>>
>> case2: 75 to 100lbf: switch disconnects power to speedbrake.  Of 
>> course what happens if you want to retract?
>>
>> case3: over 100lbf, the switch reverses the polarity.  But what 
>> happens if you are commanding a retraction?  It would go the wrong way.
>>
>> Like I said, the SPST is easiest, the DPDT auto-retract would take 
>> more thought.
>>
>> Jim Sower wrote:
>>
>>> But it wouldn't prevent you from over speeding the speed brake if it 
>>> were already deployed, or retract it automatically when limits were 
>>> exceeded?
>>>
>>> michalk wrote:
>>>
>>>> The diode would allow you to retract the speedbreak if the cutout 
>>>> switch were engaged.
>>>>
>>>> Jim Sower wrote:
>>>>
>>>>> <<flip the switch to extend the board, and let the cutout switch 
>>>>> decide when to extend it some more What would happen if you were 
>>>>> cruising at low IAS (say at 15k'), extended the board, dumped the 
>>>>> nose and accelerated to some point beyond the limit?  Sounds like 
>>>>> your scheme would prevent you from extending at excessive speed, 
>>>>> but not be able to retract it if the speed became excessive after 
>>>>> it was already extended.
>>>>> Am I reading you right? ... Jim S.
>>>>>
>>>>> michalk wrote:
>>>>>
>>>>>> Incrementally extending...
>>>>>>
>>>>>> I was just thinking about this on your first post.
>>>>>>
>>>>>> It seems it would be quite simple to add a force actuated switch 
>>>>>> that would not exceed some limit.
>>>>>>
>>>>>> I do not remember what the current actuators are rated for, but 
>>>>>> let's assume they are 100lbs.
>>>>>>
>>>>>> Make a collar that fits around the keel end of the actuator, with 
>>>>>> a spring with the appropriate K factor to move .25 inches when 
>>>>>> 75lbs is applied.  Put a switch in series with the actuator, with 
>>>>>> a diode so that the switch is bypassed if you want to retract 
>>>>>> while the cutout switch is engaged.  Normal operation would bypass 
>>>>>> the diode (no voltage drop), when the cutout switch is not engaged.
>>>>>>
>>>>>> Want to go down? just flip the switch to extend the board, and let 
>>>>>> the cutout switch decide when to extend it some more.  Just don't 
>>>>>> exceed the limits by increasing your airspeed.
>>>>>>
>>>>>> I suppose one could get fancier with a DPDT switch that would 
>>>>>> retract it if the forces get too high, but I haven't put enough 
>>>>>> brain cells into that problem.
>>>>>>
>> _______________________________________________
>> To change your email address, visit 
>> http://www.tvbf.org/mailman/listinfo/reflector
>>
>> Visit the gallery!  www.tvbf.org/gallery
>> user:pw = tvbf:jamaicangoose
>> Check new archives: www.tvbf.org/pipermail
>> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
>>
>>
> _______________________________________________
> To change your email address, visit 
> http://www.tvbf.org/mailman/listinfo/reflector
> 
> Visit the gallery!  www.tvbf.org/gallery
> user:pw = tvbf:jamaicangoose
> Check new archives: www.tvbf.org/pipermail
> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html