Tapered Axle Length

[blakecarl]

Today while putting the wheels back on our BC12-65 after doing some work on them, I noticed a problem. With the wheels on the axles as far as they will go the outer bearing is not in the correct position on the axle. Either the hub is too wide or the axle is too short. On the right wheel it is still covering some of the threads and is of a larger diameter than the axle where it sits. On the left wheel it is still covering some of the threads but appears to be close to the same size as the axle where it sits.

The hubs I installed are replacements for defective ones that were on the plane. My first thought was that I had not seated the new races completely or that the replacement hubs were wider. I measured the defective and the replacement hubs from outside of bearing to outside of bearing and found them to be the same, 6 3/8”.

My best guess is that the outer bearings would need to be ¼” to ½” further onto the axle to be in the correct position. At this position an outer bearing placed onto the axle by itself fits snugly.

I’ve checked the drawings and researched some on the forum but have not been able to find a dimension for the length of the tapered axle. What is the length supposed to be? Were there different lengths used?

Any help would be much appreciated.
Blake

[Howard Wilson]

Re: Tapered Axle Length

Hi Carl,

Hmmm, Don't have a dimension for you, but will attach the two dwings w/ the parts if you haven't seen them. Do your two axles measure the same? h

[blakecarl]

Re: Tapered Axle Length

I didn't have time yesterday to measure the left axle. Based on the number of threads beyond the castle nut on both sides it appears that they are nearly the same length. I should get to the hangar tonight and this is the first thing I'll do.

Thanks for the parts lists. Is there a document available with diagrams and lists of the other assemblies similar to the ones you attached?

Blake

[Ron Greene]

Re: Tapered Axle Length

Blake,

Drawing for L-2 tapered axle, I assume they are the same.

[Dick Smith]

Re: Tapered Axle Length

Blake, I threw a tape on the axle of an old gear that I have and measured 7- 1/16 inches from outer end to plate. This was without any brake parts installed...just a bare gear. Dick

[blakecarl]

Re: Tapered Axle Length

Ron - Thanks for the drawing! As is the usual case with me, this raises an additional question. When installed how far does the axle extend out from plate the brake assembly attaches to?

The diameters definitely match. I need to measure it exactly but believe the length of axle extending out from the plate to be approximately 6 15/16". This is possible if a portion of the axle actually extends beyond the plate, towards the center line of the plane, which would seem likely to have a solid connection. I'll also measure the length of taper, amount of axle beyond plate, etc. when I get back to the hangar to see how that compares to the drawing dimensions.

Blake

PS: After posting this message in response to Ron's reply, Dick replied with my answer. The 7 1/16" dimension I'm guessing is very close to what ours is. If this is true the hubs I have are too wide. Are there different widths of hubs available?

[3Dreaming]

Re: Tapered Axle Length

Are you sure the spacer tube did not get out of place when you put the wheel together? Tom

[blakecarl]

Re: Tapered Axle Length

Tom - I'll double check this but I recall looking at this yesterday and it appeared to be in the correct position.

Thanks
Blake

[Pearson]

Re: Tapered Axle Length

Are you absolutely certain that there wasn't still a bearing race in the hub when you installed the new ones?

[blakecarl]

Re: Tapered Axle Length

Are you absolutely certain that there wasn't still a bearing race in the hub when you installed the new ones?

Richard - I'm pretty sure there wasn't but I will recheck.

Thanks
Blake

[Ragwing nut]

Re: Tapered Axle Length

Did you loosen the shoes before sliding the replacement wheels on? You could have the shoes binding the drum up and not letting it slide all the way on.

[Pearson]

Re: Tapered Axle Length

The original Shinn wheels on my plane have the bearings 6.220 inches apart. This is measured from the flat part of each bearing, where the part number is usually etched. Put another way, for the outer bearing, it is where the washer rests up against it. And basically the same surface on the inner bearing. This was measured with a dial caliper and is fairly acurate.

Someone mentioned the spacer tube being out of place. It has been awhile since I have had one of these wheels apart, but as I recall there are some dimples in one half that have to line up with holes in the other half. Did you get those out of alignment?

I would check the distance between the outer edge of the bearings with them laid into the races with the wheel off. If it is very much more than the measurement above, I suspect you have assembled the wheel wrong. That would explain the difference between the two wheels.

Please let us know what you find. Inquiring minds want to know.

[blakecarl]

Re: Tapered Axle Length

Richard – The 6.22" width would be the perfect dimension for our axles. At least one of our hubs is stamped as Model No. 6C 4B. What model number is stamped on the hub you measured?

I did take one of the hub pairs that came on our plane and put it together with the old bearings and races in place to measure. The width from outside of bearing to outside of bearing was 6-3/8” (6.375), the same as the replacement hubs we have. Doing it this way, I could insure that the dimples were lined up. On the hubs I have had apart, there are dimples on one hub half that line up with a depression on the opposite half, except as noted below. Also, I didn’t have the center spacer tube in place so that should eliminate dimple and spacer tube alignment from being the cause.

I do have a few questions about putting the hub halves together. First, each hub half, on the face where they meet (where the dimples are) has one hole in addition to the three holes for the bolts that hold the halves together. The extra hole is where a dimple would be if the hole weren’t there. When I took the hubs apart that came on our plane, these extra holes were lined up directly across from each other. When I put the replacement hubs together, I aligned them the same way. Does it matter how the extra holes line up?

Second, is there a specified torque to be used on the bolts that hold the hub halves together? I don’t believe this by itself would change the width of the assembled hub much, but this would depend somewhat on the answer to my last question.

Lastly, in addition to the center spacer tube some of the hub halves I’ve taken apart had tubes where the through bolts go. On the replacement hubs I’m using ,I made sure all of these tubes were in place for all four halves. Are all of these supposed to have tubes?

Here are the additional items I’ve checked. The shoes are not keeping the hubs from going on further. There is only one race in place on each hub half. The axle length extending out from the plate it is welded to, is the same as what Dick had measured, 7-1/16”.

I did look at this with my A&P last evening. He felt it would be perfect if the outer bearing was another 1/8” onto the axle, but he thought it would be adequate the way it is. However, as Richard stated, “Inquiring minds want to know”. I would rather figure out if something can be changed, adjusted, etc. that would result in a better installation.

Thanks again for the help!
Blake

[Ragwing nut]

Re: Tapered Axle Length

Can you get the cotter key in without over loading the bearings?

[blakecarl]

Re: Tapered Axle Length

Can you get the cotter key in without over loading the bearings?

Depends on what would be considered "over loading". When the A&P checked the wheels, he hand tightened the castle nut and then used a wrench to tighten it to the next slot to line up with the cotter key hole. While doing this we had a jack in place so there was no weight on the wheel.