Hawk Pro .50 engine upgrade

[teamitk]

Hey all, I have been flying this Hawk Pro for a while now, am very happy with it. I live at +5,000 feet so I give up a little engine power due to the thin air. I have a lot of experience "overpowering" my airplanes to get maximum performance at this altitude, and now wish to do the same to my heli. Just looking for info from any who have done the mod. Currently running an O.S. .37 on 30% nitro. I can tell you this combo is NOT going to cut it power-wise. It flies just fine but the power is definitely coming up short. I am guessing I need to buy the Raven engine mount ant the O.S. .50. Anyone with suggestions, please let me know. Thanks.

Don

[zozie]

I'd just throw in a 50 hyper and put a long boom on it for 600 blades. You can get a long torue tube I belive as well. If you can't get one, make one from a varbon rod. The difference will be huge huge power wise.

[Chris DeSain]

I upgraded to a standard os 50 SX-H with 570 blades

just motor mount and the 14 tooth pinion gear is all I needed. I used a governor to controll head speed. No problems and was a hot 3D ship.

I went to 600 and the long boom it was a little smoother like my raven but I liked the 570 blades better. It really would never bog out with the 570 you could really pitch pump it around.

[teamitk]

Thanks, zozie and Chris....

That is exactly what I am looking to do, Chris. I don't want to convert this thing to a .50 size ship. Just want it to be a pitch pumpin machine. What is the idea behind the 14 tooth drive gear? That will speed up the head in relation to the stock 13 tooth gear, correct?

I see that the .50 hyper and the .37 I am currently running have the same effective RPM range, and both make the most power at ~17,000 RPM. I wonder if any of you math/gear ratio geniuses can tell me what head speed will be at 17,000 RPM on the engine?

Guess I should probably order the 570mm's and possibly the 14 tooth drive; but may conduct the first few flights with the new .50 installed with the stock ratio and 550's (just for testing/comparison purposes). I assume at this altitude the .50 hyper will put out more power than a .37 does at sea level; so will tune as necessary. The .50 will be here tomorrow.... weather permitting, test flights should happen this weekend!

[Chris DeSain]

Yes the stock ratio is 9.7633 and gives a head of 1741 at 17000 rpm
With the 14 tooth it gives a 9.06 and a head speed of 1875 and will make the head more lively !!

The 53 tooth counter option for the constant tail with the 14T gives a 8.73 and a 1946 head speed. That is the reason I bought the constant tail drive was for the gear....

hope that helps !

[teamitk]

Great! Thanks, Chris! I can see myself enjoying this setup... I can also see myself needing to buy a governor! Is the above mentioned constant tail drive the standard hawk upgrade, or do you need to order something special to get the 53 teeth?

Thanks for your help.

Don

[teamitk]

The conversion is done... put in the .50 hyper, and regeared it as per Chris DeSain. Also added in the .50 size fuel tank. Three flights so far, averaging 14 minutes per flight with the engine still very rich. Still running the 550MM blades; set it up for +/- 13 degrees of pitch. It is making a ton of power, even running rich. As I begin to lean it out, I suspect I may have to switch to 570MM blades. That head really cooks now! Feels like a whole new chopper (although it scares me a little... much more responsive!)

The only unforseen modification I had to make was clearancing the left frame to fit the muffler where it attaches the engine and heating and remolding the cooling duct to clear the engine head. Otherwise a trouble-free install.

[dxtarl]

How are you getting +/- 13 degrees of pitch i am only getting +8/-12 what are your link measurements?

[teamitk]

I am running the metal bell mixer arm set (century part number CN2275A) set on the inside hole off the swash linkage, and on the outside hole on the flybar linkage. I have also replaced the 2 short balls on the swash with long ones. After these mods it was extremely easy to get +/- 13 degrees; could do even more but everything starts binding around 13 degrees. Have since backed it off to about 12 degrees as 13 was proving to be a little too much for the engine. I can provide pics of my setup if you would find them useful.

Don

[dxtarl]

that would be great, i was thinking of going to all metal head, but $ is tight may little at a time.

[Chris DeSain]

I like the metal for the head speed just that little bit of knowing the blades are on a little better. But I ran it plastic for a year and I tell you the Metal in that heli did not really do much for the feel like in a 90 machine.

So not going metal is not so much performance and you can always add the mixers to plastic grips. Or change ball sizes on the plastic mixer and swash ! to seed it up

I stayed 550 for some time. I needed to load the head a bit and it would bounce a little on the tail in hanging 0 pitch moves as I had a hella slow gov servo so if you do go gov get a limiter or a fast servo and the 550 blades will be fine. 560-570 give better loading and a lighter feel so it is a win also.

I finally went 600 this year. It is more stable and better all around. just needed a boom TT and one coupler. It is not the 3D power house it was at 550 size though.