what pinion?

[istandalone]

running rcp 515's with the rcp 18 1100kv motor on 6 cells. what pinion should i use? the hs calc on readyheli says use the 22t pinion for an 1100kv motor. is that right? right now i've got 13, 14, and 15t pinions and the 15 gives me around 1770rpm and according to the same calc a 22t pinion will give me 2600rpm. what kind of hs should i be going for? i'm still learning ff and figure 8's, piros and such. loops and rolls are few and far between, so no 3d for a long time if ever. i'm looking at mostly just sport flying. thanks in advance for the advice.

[istandalone]

well, i ordered the 22t anyhow. what pinions are you all using with what kv motor and cell count? just trying to get some ideas.

[ke6d]

I made a spreadsheet to calculate the headspeed when I was trying to gear my Hurricane for the RCP H/18 motor. You should be using the 13T pinion for your H/18 motor (assuming the you are using the stock gearing - 61T main (rear) and 42T secondary (front) and 19T autorotation gear) anything above it is way too high a headspeed. The hs calculation assumes that you have an ideal setup with no drag. In real life, we normal take 10% off this number. It gives us an idea what the hs is like for a given gear setup. I have flown mine with the H/18 motor for about 2 months (60 flights because of bad weather here in Northern CA :) ) my headspeed is about 2200 rpm at 100% throttle.

I am attaching the headspeed calculator speadsheet here so you can play with it. Just change the gears and motor Kv and see what the headspeed will be.

Dan

[ke6d]

Attachment never made it up to HeliFreak because it was telling me that the file is invalid. Please PM me with your email address, I will email it to you.

Dan

[istandalone]

but there is a drag co-efficient on it. it shows you with 95% and 100% efficiency. it's calculations say with a 15t pinion at 95% eff hs will be 1777rpm. i guess i don't get why the two calcs would get different speeds, or do different hs calcs figure hs in different ways?

[ke6d]

The calculation is the same. I just checked it out. What they called main gear is actually the secondary gear (42T). If you put 42 as your main gear, the calculated headspeed is 2354 which is the same as the formula:

Gear_Ratio = Main_Gear * Secondary_Gear / Autorotation_gear/ Pinion
Headspeed = Motor_RPM / Gear_Ratio
Motor_RPM = Motor_Kv * Voltage

Dan

[Pinecone]

You have to zip it to upload.

[ke6d]

Thanks Terry. I will do that.

Dan

[ke6d]

Here is the spreadsheet to calculate headspeed for the Hurricane 550. You can expand it to add in more main gears, secondary gears, pinions, autorotation gears, and motor Kvs, then shoot for the speed that you are aiming for.

Dan

PS: I edited the spreadsheet to include all the Revco gears and pinions. Now you should be able to glance down the spreadsheet and find the headspeed for gear/pinion/motor combination.

[concept1]

I also run the H18, and with the stock gearing I ran a 14T, now i am running the revco gearing and dropped to a 21t which is about the same as a stock 13t, no way you would want to run a 15t, you would have ballistic head speed and a real killer on the batteries.