[PSUBS-MAILIST] Minn Kota 101 - thread spec

[Cliff Redus via Personal_Submersibles]

Yes 1.6 teaspoons. Just looking at the 101instalations I have seen, I agree, vinyl  length seems adequate for reservoir.

Cliff


 

________________________________
 From: Jon Wallace via Personal_Submersibles <personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
Sent: Tuesday, July 22, 2014 9:35 AM
Subject: Re: [PSUBS-MAILIST] Minn Kota 101 - thread spec
  



Cliff, if you cut the temp rise by two doesn't the volume
      displacement become 1.6 teaspoons?  Regardless, I accept the need
      for a reservoir but it would seem the vinyl tube design would meet
      that role in the case of small MK motors and can be achieved via
      extra length or diameter.  My memory of Alec's and Jim's
      configuration is that both have more than 3 teaspoons worth of
      extra volume in their tubes and perhaps this is why they haven't
      seen issues during dives.

Jon





On 7/21/2014 9:47 PM, Cliff Redus via Personal_Submersibles wrote:

 
>Concur Jon that water will act as thermal sink and that the duty cycle on the thrusters are not severe but I don't agree that the thermal expansion in negligible. If you assume that the temperature change I estimated was high by a factor of two, then you would still end up with 3 teaspoons of oil that would be forced into the ambient tube.  Small but not negligible.  There will be a change in the internal temperature of the motor from the off position to on and given the amount of oil in the 101 body, there will be  oil that has to escape.   
>
> 
>Granted, the primary purpose of the compensation is to keep from exposing the housing to a high differential pressure but thermal expansion still has to be accounted for in sizing the ambient reservoir. 
>
> 
>These MK 101 are powerful at almost 1.8 HP at 47 amps when air filled  but there has to be some degradation in power when filled with oil due to the viscosity difference with air. At 75F, light oil is over 1800 times as viscous as air. IS there enough power to push a psub about, sure.   I am just trying to come up with what kind of HP loss you get with oil compensation.  
>
> 
>Does anyone know what rpm these motors max out at in the water? 
>
> 
>Good point Vance on trying to make the armature as hydraulically smooth as possible to maximize power when oil compensated.  I wonder how hard this would be to do? 
>
> 
>Cliff 
>
> 
> 
> 
>  


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