Modifying Engine Bearings 1

[MNRaptor]

We are building a destroked V6 by offset grinding the crank journals and having custom rods made. The new diameter of the journal is the same as another engine we work with often however the width of the rod is .200" less. If we wanted to use the bearings from that application, is there a good method to make the width appropriate? I would like to use the ACL H rated bearings which do not have the flash coating on them found on most bearings.

Thanks in advance,

Mike

 

[willeng]

MNRaptor

Unfortunately i do it all the time
Turn & smooth down a piece of Timber to the journal size plus your (bearing clearance & add about .001" or so). Lay your bearings around this & use a small band clamp to firm them up lightly, it's just a matter of spinning off the bit you don't want, use coolant & take your time. Just debur & chamfer the cut on both sides & your done!

Leave a good step to butt the bearings up against for initial fitting & get the band clamp up as close to the cut as you can.


Hope this helps

 

[MNRaptor]

Thanks for the info, that is an idea I hadn't considered. I will try it out, sounds like it should work well. I was going to try using a surface grinder if I could find a decent method to clamp it, but this sounds like it should work fine.

Thanks again

 

[SMOKEY44211]

If you are just doing a one time modification for this application I think the most time effective procedure would be to simply block the bearing shell with 3 blocks that are slightly smaller then your desired finished width. Set one block across the parting line and triagulate the other two to support it in the radial side. This is assuming you are using grinding method. Same technique will work with a magnetic chuck on a milling machine and fly cutting tool. You can do two shells at a time by setting the second bearing against the block that is set across the face and block that one accordingly. If the crank you are running has indivindual crankpins for each cylinder(example even firering 90deg V6)you probably want to center the finished bearing in the rod. Pretty easy to guage and cut both sides accordingly. Odd fire where two rods share a common crank pin you might do well to offset the bearing away from the cheeks of the crank especially if there is a large radius ground into the crank pin.---------Phil

 

[patprimmer]

Another simple method is to use a junked rod from an engine that takes the bearings you are going to use. Cut the rod just above the big end and clamp the bearings in the rod big end then use this in the magnetic bed as described by Smokey44211.

I would narrow the rod big end to the desired width before doing it with a bearing shell inserted.



Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[MNRaptor]

Thanks Pat and Phil, That sounds like a better option. I have plenty of dead rods to modify for that purpose. That definately sounds like the best way to go.

 

[motorsportsdesign]

Be sure to put a chamfer on the edge of the bearing to c;ear the crank radius. I have always done this with an arbor and hose clamp in a lathe. Or in a rod with a fly cutter in a mill. I cut the form I want an a flycutter and plunge it down on the bearing.

One advantage of the lathe method is that it is easy to dedurr the cutt area. I often used abrasive impregnated bubber for the deburring.

Grinding soft material sounds like a drag.

Jonathan T. Schmidt

http://www.schmidtmotorworks.com