For the Dan's and Volvo Guys - tapered bearings

[Dave B]

.... and I wondered what's the most total weight anyone has hung off that wheel bearing and how long has it been flying ? I keep telling myself that the rear wheel hub, tapered bearings also that is from a Caravan must have at least 400-500 lbs. on it constantly and as long as everything is balanced (no problem). It's just hard for me to see things in reverse I guess. Each blade is almost 10 lbs. The rotor & magnets must be another 10 lbs, I have wooden disks as spacers and plates for the "sandwich" mount so I'll guess another 10 lbs, say a few lbs. for bolts & nuts etc. I'm guessing total weight hanging on the bearing will be up to 60 lbs. I've replaced the bearings, races and seal and will pack it with grease after balancing so it's new. So, the big question is : how much can these bearings take ? Someone please boost my confidence a little. I know that just spinning is nothing compared to the abuse and weight on it when on the vehical, it's hard to convince myself. Thank you for any thoughts.  Dave B.

[windstuffnow]

  Dave,

    Personally I don't think there is anything your going to do to overload that wheel bearing.  Consider the load on the the front wheel in a hard turn, where two bearings are carrying the load plus the g factor.  A good portion of the vehicle weight is transfered to the one outside wheel.  I highly doubt your machine will see loads like that.

     Your only using it for the yaw bearing right?  If so, then your only loading the bearing with the weight of the machine.  I don't remember the maximum thrust load they will handle but it is quite high ( 1200 lbs + ).

Have Fun

Windstuff Ed

[windstuffnow]

   Ok, just checked one of my bearing books... The standard tapered roller bearings such as used in trailers has a maximum "thrust" load of 9300 lbs or a maximum "radial" load of 18,830 lbs.

    I had looked it up before because I use them on my slotted stators.  I had figured the thrust load with .060" clearance with 16 magnets was up around 700 lbs.  With only 12 magnets it droped considerably.

    Needless to say, I don't think your machine will see loads like that....

Have Fun

Windstuff Ed

[Dave B]

Thanks Ed. The bearing is from the rear of a front wheel drive Caravan so less thrust load than front but safe anyway. I want to use the same for the yaw bearing to ease assembly of my alternator. Any ideas on slowing down the movement to be less sensitive to yaw ? By the way, a 12' rotor will pass through an 8' sliding door if you have the headroom ! Basement is too small to finish the job so I'll assemble it in the loft and carry it outside. Thank you for the information on the bearings, I guess as long as everything is well balanced I should be OK. Dave B.

[bob g]

I am with Ed on the capability of the tapered brgs being sufficient to handle most rotors in most conditions.

perhaps with large rotors over 12 foot or so and turbulent conditions you may experience some shorter life cycle.

also it is worth noteing that while a brg may have a hundred thousand mile expectancy before being cleaned and repacked on a car, on a wind machine this amount of use can be reached in under 6 months in good wind area's.

The use of high quality seals, with an oiler cap, and synthetic oils will likely extend the useful life of the brgs in any case.

bob g

[iFred]

I totally agree with Ed. I don't think you have anything to worry about. I talked to some auto mechs, and they tell me at worst case, lube the bearing every 6 months and check the bearing for wear at that time. I think your safe on all fronts.

Someone uploaded the blade force pic about  a week ago... so I'll go by this if i'm correct...taking the worst case that could happen... A 15 ft  blade with a 75 mph wind speed would give a max of 6000 pounds of blade force. I am assuming that the force would be directed at the entire blade and therefore produce a net total force on the main bearing by the same amount. Best guess.

That bearing can handle double that, according to Ed's calcs.

[Dave B]

Great information guys and thank you for easing my mind. I guess I have a hard time thinking in reverse about the weight (axial) load hanging on the bearing, I've been less concerned about the thrust load. Hard for me to imagine 500 lbs hanging off the bearing, such as the case on the vehical and taking all the road punishment besides. I can't wait to at least get this on the test tower to balance it, that's the next project. Hopefully after that I'll have the mount and furling system worked out, photos to follow. Thanks again,  Dave B.

[Norm]

I don't know for sure but what happens if a bearing does fail...seems like it would probably get hot,seize up and stop??? at least on a windmill...of course on a ton of car going 60 mph or so would be a different story...

           ( :>) Norm

[monte350c]

Hi Norm,

I've seen a couple of tapered roller bearings fail and it usually has to do with water or grit getting into the bearings. If the units are well sealed up and periodic maintenance is done there shouldn't be any problems at all.

The failures I've seen were accompanied by lots of grinding and rumbling noises and a big increase in play in all directions around the shaft. The rollers were missing upon disassmebly. In both cases the outer dust cap had fallen off...

Ted.