Wednesday, May 28, 2014

Re: [Electric Boats] Re: Direct drive and thrust bearings vs flange mounted ballbearing

 

Hi John,
Thanks for all the input, your calcs helped me with my own loads. Glen-L does have a double row flange mounted thrust bearing designed  specifically for marine use.
This is the first flange mounted thrust bearing I've been able to find. Thank you King of N.O. for the heads up.(New Orleans is one of my favorite places, such great character). What a great website you have John< I'm jealous of your double ender ! Well planned and executed conversion. Very clean and nice lines. I'll be fabricating a SS pan to mount both motor and bearings, Your motor mount is a thought, suspension rather than mounting. Was this a Lynch suggestion in desiJohngn?
 
Thanks both of you for your input, King when will you be starting your project? I too would like to hear how thing progress.
John, calm seas and steady winds to you across the pond!
I'll keep updates flowing, and look forward to you input here. I learn something new everyday!
 
Jim

From: "fitloose" no_reply@yahoogroups.com.
To: electricboats@yahoogroups.com
Sent: Monday, May 26, 2014 4:42:56 PM
Subject: [Electric Boats] Re: Direct drive and thrust bearings vs flange mounted ballbearing

 

Hi Jim,


Just to be clear I am not using a separate thrust bearing. I'm using  the Lynch motor  bearings to take the loads, which there are  two off in the motor of the types below,

3204-2RS or the 3204-2Z.They differ I think by seal/friction/lube.

3204-ATN9 SKF Double Row Angular Contact Ball Bearing - Polyamide Cage :: BearingBoys.co.uk


I ran through some basic calcs with SKF for a 3204 type ref


http://www.skf.com/uk/products/bearings-units-housings/ball-bearings/angular-contact-ball-bearings/double-row/index.html?prodid=125002204&imperial=false


Shows static of 20kN and dynamic of 12kN but does not account for operating conditions.


Even in my case of estimating an axial shock load  worse case surfing down waves past hull speed gives gives say  static load of 3kN (675lbf) axial on shaft. I think on say a 10m sailboat with locked 3 blade 14" prop gives a drag of about 45kg (100lbf) at 7 knots when sailing which is nearly 1/2 the drag of the hull at that speed?



I called SKF and we used


http://webtools3.skf.com/BearingCalc/selectCalculation.action


My calcs/results below. The EP warning if I recall correctly from my apprenticeship means Extreme Pressure (grease/oil)


Bearing life : 3204 A-2Z/MT33


Results

L10mh 
SKF rating life, operating hours 		 2310 hour
aSKF 
SKF life modification factor aSKF 		 0.114
κ 
Viscosity ratio 		 0.17
P 
Equivalent dynamic bearing load 		 4.04 kN
ηc 
Factor for contamination level 		 0.0569
ν1 
Required kinematic viscosity for κ=1 		 153 mm2/s
L10h 
Basic rating life, operating hours 		 20200 hour
L10 
Shielded bearing grease life 130		 77500 hour
C/P 
Load ratio 		 4.95


Warning

Viscosity ratio κ=0.17 is less than 0.4 - a lubricant with EP additives should be considered. t


Input parameters

Fr 
Radial load 		 .5 kN 
Fa 
Axial load on bearing 		 3 kN 
ni 
Rotational speed of inner ring 		 100 r/min 
Bearing operating temperature 
Bearing outer ring 		 70 °C 
Grease used in the bearing 
Select from list 		 MT33 
Viscosity at 40 °C 
 		 100.0 mm2/s 
Viscosity at 100 °C 
 		 10.0 mm2/s 

Jim - I can't say for 100% certain what is right for you. I'm happy with what I have. At the end of the day, I'm not commercial, just one guy with a limited budget and no funded R & D dept. In that, there is risk.


Personally if I were in your shoes I'd go for a conventional thrust bearing arrangement. I think Cal is commercial so maybe he knows what is best for you but I'm not clear what he has built. I have no experience of Motoenergy motors, only my system which I have documented with my learning curve on a public Facebook page.


Elektra Yachts


John


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