Detail layout for rotor retention-quadcopter.

[Owen N]

The Quadcopter design, without the cyclic pitch control, seems to develop massive bending torques at the rotor head mount, when cruising at speed. (5m rotor) I looked at some helicopter shaft-rotor join detail drawings on Pinterest, and they seem much lighter built.

Has anyone seen drawings for a system which produces bigger bending torques? the 1.5 inch shaft is way too small, and the gearbox
cannot fit a bigger shaft without needing to be massively scaled up.

I was thinking spline drive into a top-hat, and a ring of bolts holding the rotor-head base-plate in place (a little like a gyrocopter head arrangement). This would require a set of ball thrust bearing races with a 6 inch center bore, which seems rather big.
Is there a more compact way of doing this?
The size is dictated by the ring size of pinch bolts needed to resist the bending moment.
The thrust bearings would be mounted in a sandwich housing, and then bolted to a custom gearbox housing,
or through-bolted with long bolts to pick up the coupler housing at the other end, which the electric motor is also bolted to. The gearbox is single-stage epicyclic, so fairly short. See my other thread on gearbox selection.

I suppose I could use a massive hollowed spline shaft with thread, say 2.5 inches diameter, then a a step to support the rotor hub, then a big thrust bearing flange, and the gearbox output shaft running in another spline inside the stub shaft. Making it one piece is a bit of a stress raiser...
This would bring the thrust bearing race center holes down to about 3.5 inches.

 

[Owen N]

I had second thoughts about this: thrust bearings are not supposed to be used for offset and angular loads. Possibly roller-type thrust bearings can be used to retain the rotor, with roller bearings to take the bending loads. inner races can be located with tubular spacers. A tubular outer tower is required. the top outer race can be retained by a bolt-on ring. roller location can be either by the inner or outer races. Finish the whole lot off with seals and provision for oil circulation. - next-to the catalogs!

It all sounds a bit complicated to accommodate a standard gearbox output. The 2.5 inch output could be built into the planet gear, and some of the bearings could be supporting the sun wheel in its overhung mount.

Which version is best? They would have to be drawn up, and do a mass/quantity/cost analysis on each... Is the planet carrier usually overhung on the input shaft? how would they have a flange end on the input shaft? pressed up-assembly with a keyway?? (from an example in a Parker catalog. I don't think they were intended for 100 % duty cycle, though they didn't make that clear in the catalog.)

In a radial engine reduction box, the anti-pullout thrust bearing must be behind the sun wheel. maybe a flat, whitemetal-coated washer with grooves?

 

[Sparweb]

It's hard to understand what you intend to build. The (5m X 4 rotors) size suggests a complex and costly effort. That you haven't taken seriously in your other posts. This isn't something you can order out of the Parker-Hannifin catalog. Your post reads like musings rather than a coherent strategy. It is wayyyy to early to decide if the mast is 2.5 or 3.5 inches diameter or not.

Read Ray Prouty's book. And Wayne Johnson's for a deep dive into the math. Look for Jacobs if you want lots of illustrations, readable style, and enough math to get insight into what you need to do.

If you refuse to do the minimum research, then you're wasting our time.

http://www.sparweb.ca

 

[Owen N]

I have suspended this as a project for now. It might make a better case with fuel cell technology, but this seems to be immature and not widely accepted. For instance no work on hydrogen production at the point of sale in being reported widely, or on sustainable central production of liquid hydrogen and cryogenic distribution. I consider widespread cryogenic distribution as being a major safety risk, and why car manufacturers prefer to convert it to high pressure gas for use in cars.

I consider this renders it way to bulky to use sensibly in aircraft, so another method is required.

Electric storage, too, has a long way to go before the mass/energy is even in the same order of magnitude
as liquid hydrocarbons. I await further developments with interest.