470mm blades on a Protos?

[Ecaf]

Coming soon!!!

http://www.rcgroups.com/forums/showp...postcount=6323

"So, is anyone interested in a 470mm Protos?"

http://www.rcgroups.com/forums/showp...postcount=6325

"No ETA yet. Still testing... Hopefully in the May/June time frame..

Really it boils down to a boom and belt. Belt mold is already made, booms will be ordered when all tests out...

New blades will be made by SAB... (SAB dropped that size a while ago from the ECO8, but it will be the red devil and then look will change when their new look is released.)"

[henryd123]

I wonder if the stock plastic blade grips are up to the extra loading

[Ecaf]

Im sure it is if the factory is supplying these kits.

[whisperdancer]

I will believe when I see it...

[edwinkoolen]

I know they are working on a stretch Protos in Germany, but there they want to buy the belt, but their diswcussion is about gearing and motor possibilities.
http://www.rc-heli.de/board/showthread.php?t=132754

Edwin

[whisperdancer]

If it oficially happens, it will be the final nail on my T-Rex 500...

[Ecaf]

Originally Posted by whisperdancer

If it oficially happens, it will be the final nail on my T-Rex 500...

Better stock up on hammers then!

[whisperdancer]

Originally Posted by Ecaf

Better stock up on hammers then!

I really hope so.
It would be the perfect excuse to sell it.

[Shawn Behrens]

I wouldn't worry about the extra load on the main grips as much as the extra load placed on the tail mechanics. The protos only has radial bearings in the tail grips. The tail will be worked even harder trying to keep tab with a head swinging 470mm mains. I would really like to see a MSH thrusted tail grip option even if this larger blade thing doesn't materialize.

shawn

[JustPlaneChris]

Originally Posted by sbmon

I wouldn't worry about the extra load on the main grips as much as the extra load placed on the tail mechanics. The protos only has radial bearings in the tail grips. The tail will be worked even harder trying to keep tab with a head swinging 470mm mains.

I guess I don't follow your logic here. Unless you dramatically increase the headspeed (and you wouldn't, you'd decrease it) the centrifugal loading on the tail grips will not change.

So unless I'm missing something obvious, this stretch would actually decrease the need for thrust bearings in the tail grips since they won't be spinning as fast.

[gravydrive]

Originally Posted by JustPlaneChris

I guess I don't follow your logic here. Unless you dramatically increase the headspeed (and you wouldn't, you'd decrease it) the centrifugal loading on the tail grips will not change.

So unless I'm missing something obvious, this stretch would actually decrease the need for thrust bearings in the tail grips since they won't be spinning as fast.

You will most likely need longer/heavier tail blades.

[JustPlaneChris]

I doubt it. Yes, the main blades will be longer, but so will the tailboom. This will give the tail more leverage and authority. I suspect it will all equal out, but time will tell.

[gravydrive]

If that's the case, why don't 90s use 70mm tail blades?

[heliboy88]

If that's really the case, maybe the KBDD longer tail blades will solve the problem?? If yes then KBDD can sell a lot more of the longer Protos tail blades they made.
Back to the topic, do you guys think a different motor, ESC and lipo should be used for this stretched Protos? Also the cyclic servos, do you think the ones used(eg. 9650) now don't have enough torque for the head swinging 470s?

[dhoff002]

Those servos should be fine, the logo 10 flew on 500mm blades, with 9650's, and it is really a streched 500 class model.

The logo 400 is really a logo 10 with a shorter tail boom and belt, and running 430 mm blades.

Dan

[Ecaf]

Originally Posted by gravydrive

If that's the case, why don't 90s use 70mm tail blades?

Perhaps its because of the drastic increase in power and torque? Also, the difference between a 600mm and 690mm blade is 14%. 430mm to 470 is only 9%.

Not saying thats the case, but Im just throwing that out there....

[JustPlaneChris]

Originally Posted by gravydrive

If that's the case, why don't 90s use 70mm tail blades?

Now you're just being silly. We are only talking about a mild stretch here. I've done it on smaller helis (King V2 stretched to 300mm, and Mini Titan stretched to 350mm) and the tail authority was better using the same size tail blades.

Originally Posted by heliboy88

Back to the topic, do you guys think a different motor, ESC and lipo should be used for this stretched Protos?

Nope, because with larger blades you can run a reduced headspeed and still get the same "pop".

[Tail boom]

Originally Posted by JustPlaneChris

I guess I don't follow your logic here. Unless you dramatically increase the headspeed (and you wouldn't, you'd decrease it) the centrifugal loading on the tail grips will not change.

So unless I'm missing something obvious, this stretch would actually decrease the need for thrust bearings in the tail grips since they won't be spinning as fast.

Hi,

Could the longer main blades have a higher drag coefficient? That would mean that the tail would have to counteract more torque. On the other side, you are right with the lower head speed. It could be a wash in that case.

Regardless of the main blade size, I do not see that much more stress on the tail blade bearings (even if you added longer tail blades). Actually, since the tail blade bearings are radial bearings, and the main blade torque creates a sideload on the tail, the tail blade bearings would be doing exactly what they were designed for: taking a radial load. The only reason for thrust bearings would be if you added more weight to the tail blades or tail blade grips, which would pull on the tail grips more as they spin (that axial load is what is bad for radial bearings).

Hope this makes sense.

Best,
Frank

[whisperdancer]

Actually, the torque is a force vs a distance.
If the tail is going to counteract the torque of the main rotor, it needs a force in the oposite direction (using the thumb rule).
So, in order to produce the same torque in the body of the heli to counteract the one in the main blades, a longer tail needs less force, and a shorter one needs more.

This means if the torque is greater with longer main blades, the force in the tail blades will be roughly the same because of the longer tail.

[CatchmyCorsair]

Sounds like a cool project. I definitely want to try it!

IMO, the Protos could use a thrusted tail even with 430's. I had 2 bearings go bad in 70 flights, no crashes or tail blade strikes.