Denso Alternator dropping offline

[lr172]

Yes - it was a PP alternator, the cavity in the SRE was worn, and the bearing had "spun". Root cause was unknown, but speculated to be heat related.

There is/was nothing visibly different in the SRE/bearing assembly or parts between the PlanePower and Genuine ND, WAI/Transpo, B&C or other clones. There is no retention of the rear bearing in these 106MM units -- press fit and wave washer.

It's possible that the aluminum alloy used in the casting is different -- maybe it had a different response to heat (maybe a little more or less of any number of alloys in the mix.)...

Thanks. I said bearing retainer, but meant bearing cavity. Yes, words matter, I know.

 

[lr172]

There is/was nothing visibly different in the SRE/bearing assembly or parts between the PlanePower and Genuine ND, WAI/Transpo, B&C or other clones. There is no retention of the rear bearing in these 106MM units -- press fit and wave washer.

Most alternators I have seen only press one bearing into the case. The other is usually a slip fit with a wave washer to keep axial compression of the bearing to keep it spinning. are these NDs different in that regard? I know that they can also keep the shaft a slip fit as an alternative.

 

[bjdecker]

Most alternators I have seen only press one bearing into the case. The other is usually a slip fit with a wave washer to keep axial compression of the bearing to keep it spinning. are these NDs different in that regard? I know that they can also keep the shaft a slip fit as an alternative.

It seems that ND (and all the clones) have two SRE bearing retention strategies. The 106MM case and below uses a press fit/wave washer into the SRE, and 118MM case and above uses a steel plate with 3 studs and screw, the bearing is pressed into this plate/collar (pic).



The above retention is superior as it is Steel (bearing) into Steel retention (Same expansion rates, etc.) It's also more serviceable -- if the bearing does spin, you can just replace the plate instead of the entire casting. Note the rectangular holes for stator wire pass thrus -- these accommodate the vibration isolation inserts, no more broken stator wires. And, the stator wires have proper terminations for connection to the rectifier; not the BS "home-electrical bare-wire-under-screwhead" connection that the 106MM and smaller units utilize.

 

[lr172]

It seems that ND (and all the clones) have two SRE bearing retention strategies. The 106MM case and below uses a press fit/wave washer into the SRE, and 118MM case and above uses a steel plate with 3 studs and screw, the bearing is pressed into this plate/collar (pic).

View attachment 100922

The above retention is superior as it is Steel (bearing) into Steel retention (Same expansion rates, etc.) It's also more serviceable -- if the bearing does spin, you can just replace the plate instead of the entire casting. Note the square holes for stator wire pass thrus -- these accommodate the vibration isolation inserts, no more broken stator wires. And, the stator wires have proper terminations for connection to the rectifier; not the BS "home-electrical bare-wire-under-screwhead" connection that the 106MM and smaller units utilize.

Thanks for the detail here! So nice to have an alternator expert "on staff" here at VAF.

 

[BillL]

PP could do this on the 60 amp if they would spend .02% more (of the sales price) on the manufactured cost. Alternatively, there are a lot of Denso alternators with the expansion rings on the outside of the SRE bearing outer race. It solves the problem. I got a quote from the bearing manufacturer (NTN in Taiwan) for these bearings of less than $3 but I would have to buy 5000, so decided not to do that. Mostly because they would not share the specifications of the original bearings and I was guessing. An unaddressed issue is that the bearing design is not patented for the US.

Thanks for continuing the alternator design/failure analysis effort.