Crankshaft bearings....pls help!

[Drei]

Hi,

I am building a new engine from my own design and i am confused what type of bearings i should use on the crankshaft. In the front of the engine i am going to use two ball bearing with one of them just 1mm apart from one of the crank throws and the other ball bearing will be in front of it. Because the crank has two throws i will also support the other end on some type of bearing. The bearing in the end will be located (housed) in the crankcase backplate (cover). I was going to use a needle roller bearing to be able to remove the backeplate easily because as you know a ball bearing would be almost a press fit on the shaft therefore i wouldn't be able to remove the backplate easily once i would assemble the backplate. Thus a needle roller bearing would be ideal to use because of it clearance between the crankshaft. The question is will ill be doing something wrong if one one end of the crankshaft i will use ball bearings and on the other end i will use a needle roller bearing?? ???

Thanks

 

[arnoldb]

Hi Drei

From what you describe, I cannot foresee any problems using the needle roller bearings on one side and ball bearings on the other side - you should be just fine doing that, as long as you have a way of retaining your crankshaft in there. The needle rollers will allow a lot of axial (in line with your crankshaft) movement, and as you have not mentioned how you will maintain the crankshaft in place, it will be down to the roller bearing on the other side to do the retaining; which shouldn't be a problem, as most normal ball bearings can take slight side-loads.

Regards,Arnold

 

[Artie]

Hi, the only issue I can think of is lubrication, what you are intending is not unheard of in the model aero engine world but they use mist oiling with crankcase induction. The front bearings could be sealed and be pre lubricated but the needle roller cant. It wont require much so perhaps regular plate removal and hand oiling may suffice.

Good luck.

Artie

 

[Ed T]

Seems to me that needle bearings need to run on a hardened shaft since there is no internal race. May not be a big issue with the low speeds and loads associated with the typical engine here. Maybe a simple oilite would be a better/simpler choice. Billions of alternators, generators, and starter motors have worked fine with this arrangement