Cummins Spinners

Graham · #1 01-01-2018, 10:37 PM

Folks,

I am fitting a Cummins aluminium spun spinner to my almost completed RV6.

The Cummins installation instructions do not require the spinner to be checked for "tracking" of the nose as the Vans instructions do. This is presumably because there is no need to trim the aft edge of the Cummins spinners, whereas the Vans spinners need trimming.

Can those of you who have fitted these spinners please advise whether they bothered checking the tracking prior to drilling the spinner backplate & fwd plate.

Thank You
Graham
New Zealand.

Ironflight · #2 01-01-2018, 11:57 PM

Ours was dead on, without any need for adjustment.

Larco · #3 01-02-2018, 08:37 AM

Same here, dead on. We love our spinner! :-)

pilotkms · #4 01-02-2018, 09:33 AM

I mated the back edge of the spinner to the back edge of the backplate. In addition to appearing properly centered visually, I subsequently Had my prop dynamically balanced and the balancer advised it had no impact and he had to remove the VERY thin shim-weight that was installed on the prop by the factory to remove the SMALL amount of vibration.

Hangar 1271 · #5 05-29-2018, 01:49 PM

I am installing a Cummins spinner on my RV-8. The installation instructions call for 7 screws in the forward plate and 14 in the aft plate. Well, why does one need the 7 forward screws? Certified planes with aluminum spinners don't have them. Does anyone have experience and an informed opinion that might answer this question?

Thanks,
David

Bavafa · #6 05-29-2018, 01:55 PM

I also like to know the measurement for the front screws. The instruction says 9-3/16" but my measurement doesn't put that right in the center of the front spinner. Also, I think there is 6 screw in the front and not 7. The instruction youtube video says 7 but if you follow it and mark it, you will come with 6 screw.

Hangar 1271 · #7 05-29-2018, 02:12 PM

You know, I just finished the drawing for the forward screws and hadn't even realized I drew 6 following their instructions but heard, and remembered, 7. Very good point.

I don't think the goal is to put the forward screws in the middle of the spinner but in the middle of the forward mounting plate.

az_gila · #8 05-29-2018, 03:09 PM

Quote:

Originally Posted by Hangar 1271

I am installing a Cummins spinner on my RV-8. The installation instructions call for 7 screws in the forward plate and 14 in the aft plate. Well, why does one need the 7 forward screws? Certified planes with aluminum spinners don't have them. Does anyone have experience and an informed opinion that might answer this question?

Thanks,
David

My Tiger has 16 screws in the aft prop bulkhead and 6 in the forward prop bulkhead.

Early models only used screws in the aft bulkhead but were soon replaced by a Service Kit that has the screws and forward bulkhead described above.

Bavafa · #9 05-29-2018, 04:23 PM

Quote:

Originally Posted by Hangar 1271

I don't think the goal is to put the forward screws in the middle of the spinner but in the middle of the forward mounting plate.

This is what I mean, in the middle of forward mounting plate FLANGE.

Please let us know how your measurement jibs down with this.

pilotkms · #10 05-29-2018, 07:52 PM

I made my back plate mounting holes every 30 degrees. An easy measurement for 12 bolts. Good luck with 14 back plate screws.
Also makes 6 bolts for the front plate rather easy.
Yes, u want the holes to be in the center of the front plate flange. I followed the directions and they worked.
As to why - someone else with an engineering degree can calculate the force being exerted as that thing spins at 2700 rpm. I wouldn’t leave them out. I have seen some RVs without the front plate bolts but the builder did much more engineering and added substructure in their assembly that was way beyond me.