Ang.:Re: [electricboats] Material Choices and Thrust Bearings

Dan, 34CrNiMo6 is for hard working shafts, and easy to machine in properly sized lathe, given the right treatment is done before machining.

It is NOT stainless steel, and thus, not prone to "self-hardening".

Please google it.

I don't know your machining skills, but please contact a shaft machining shop (I did not say ANY machining shop) with your design at hand. This is definitely not a DIY novice job.

There seems to be a tendency to choose standard trailer wheel hub bearings lately in this forum, mostly triggered by the Thunderstruck (etc.) base plate designs.

The shaft of a propeller has mostly only (bi-directional) axial forces, exept where we connect our belt pulley.

A hub bearing is meant to deal with radial forces, and some axial forces.

There are torsional forces too.

My suggestion is to use a double roller spherical bearing, set in a proper housing.

I contacted SKF (the inventor), and they recommended this bearing for this purpose.

(Hmm, maybe I should mass produce a range of housings ? ;-)

For corrosion, Dan, your shaft is to be in the engine/motor room, and not submerged (I hope), so it should only be protected for exposure to humidity, like a car body.

A clear Dinitrol spray will do fine.

Priming and painting looks nice, but ehh, not necessary for a simple shaft, right ?!

I hope this information will be useful.

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På fre., den 26. mar. 2021 klokken 1:45, Dan Pfeiffer

<dan@pfeiffer.net> skrev:

Carsten,  That'll do.  Always good to know.  Thanks.

At first glance to my novice eye the specs the material you specified looks fairly tough to machine.  Is the comparative machining issue with SS due to work hardening? 

What would you do to protect the alloy steel shaft from corrosion? 


Dan Pfeiffer

 

On 2021-03-23 4:09 pm, Carsten via groups.io wrote:

 

Educated machinist at a nuclear test facility in Denmark.

Worked as production planner and programmer of CNC multiple axis lathes and milling machines for 18 years

Switched to large marine producers, writing procedures for manufacturing, and tested production methods at suppliers

Worked in Asia for 10 years, educating and teaching many of the production facilities of large Diesel engine manufacturers in South Korea and China, and assembly of engines at the shipyards

Made the crankshaft production in China feasible for them

 

Now retired (and actually tired of chinese taking over everything (because of me, partly)).

 

Is that ok for you, Dan ?

 

In short, SS is not easily machined.

Go for my selection, then you'll have an easy time at your lathe.

I'm sure that you can look up the equivalent of my material in a comparison table.

 

Cheers !

 

 

On Wednesday, 24 March 2021, 04:23:21 GMT+8, Dan Pfeiffer <dan@pfeiffer.net> wrote:

 

 

>>Hi, Dan

>>I will suggest 34CrNiMo6 alloy for your shaft.

>>>

>>>On Friday, 19 March 2021, 07:07:01 GMT+8, Dan Pfeiffer <dan@pfeiffer.net> wrote:

>>>Carsten, You mentioned that I should not bother with stainless steel for my small output shaft.  What would you suggest for that instead? 

I found this info:
https://steelnavigator.ovako.com/steel-grades/34crnimo6/

Is a 4340 a similar alloy? I can get that from McMaster.  Cost is the about the same as SS.  How hard will it machine in my lathe?   I was prepared to machine the SS.  Will this be tougher? 

Also, I am figuring you have some background in all this? 

Thanks, Dan Pfeiffer