Rev Limit

[kfxguy]

Wrong, not universal on the boards. Too many newbies (and others) refer to unloaded rpm - Kv times nominal voltage which for Neu, Leopard, TP etc. is not realistic. You have to ask to be certain.




.

I'm no pro here, but I would think that prop, battery health, battery capability (output), motor power, motor size, weight, prop size, prop pitch.... would ALL have a bearing on your loaded rpm. Any voltage you'd use to figure your loaded rpm would be a guess at best.....some people are just better at guessing because of experience........ I guess the only true way to know is to log it. But.....I figure target rpm based at 3.7v loaded because with a "correct" (I use that loosely mind you) setup, it is a good number to use....in my limited experience.

[Fella1340]

Tyler, congratulations on the speed record. I didn't see a post here on it. How fast did you go and in what boat? Of course details are welcome like- motor kv, voltage, prop and complete boat drawings with detailed setup and any logged info:-D. I may be holding out for the last bit of info but seeing a few pictures of the badboy and any video would be very cool. Our very own boatstar here on OSE! Awesome!

[RaceMechaniX]

Fella1340,

Take a look here http://forums.offshoreelectrics.com/...th-Sun-Nov-9th for the thread on the SAW event.

The new record is at 142.94mph. I will say I used a Lehner spinning a custom stainless prop around 50kRPM loaded and the boat drawings, models, files you only get to see if you come to the lake.

[Fella1340]

Thanks Tyler, since I don't race it was in a very unlikely spot for me to find. But find it I did! Hats off to you, how do you top the top spot?

[keithbradley]

50k for 22 and 30 series. 19 series are higher.

A few things to remember/consider though...

-50k loaded isn't 50k unloaded. Consider things like prop unloading if/when it comes out of the water and the effect it will have on RPM.

-Most Chinese collets are not true. Many flexes are not straight. I tested maybe 20 or 30 collets one day and every one was noticeably "wobbly". Driveline harmonics can and will cause motor failure. While the motor is capable of 50k RPM, vibration from driveline issues can cause failure at or well below that.

- Power is relative to Torque*RPM. Turning the same prop faster will take more power. In order to keep power demands reasonable at 60k RPM, you would likely need a prop to small to be practical and efficient on most boats.

- Since Lehners are rated under load, DON'T compare kv ratings/performance of kv ratings to motors like Neu/TP/castle/Leopard/etc. For most purposes, multiplying LMT kv by 1.15 will get you a Neu motor that is close to the same theoretical RPM (for example a 1600kv LMT will compare to a Neu around 1840kv). This varies depending on motor size, but I find 1.15 to be pretty close for most applications.

[Mike Caruso]

Tyler,
Thank you for this information it explains a lot more to me. I have been trying to get my head around everything here that you just cleared up.
Mike

[T.S.Davis]

Nice chart Tyler. I found it encouraging that my favorite setups fit nicely into it.

I had a giggle at Fella1340's expense. Sorry man. I know you don't mean it like this but I remember when Joerg shocked us all at 140mph. Some wanted every detail of how he did it. Now it's Tylers' turn.

So Tyler, will you build me one just like yours please? Might need you to drive it too.

[RaceMechaniX]

Good one Terry,

I don't mind being asked on the set-up. I am always open to helping others improve their knowledge to point, but some things must be learned by trial and error.

While I will not build you one I may let you drive one in Flint at the next event. Of course I need to let Terry Keely try it too.

TG

[Fella1340]

I was thinking having it all served up on a silver platter might be a stretch... But I had to ask. I don't really have any idea what it takes to run at that level, give me 15-20 years to catch up!

[T.S.Davis]

Dedication, patience, and a willingness to let go of an idea when you find yourself heading in the wrong direction.

Speculation on my part though. I'm not going there either. Sometimes I have all those but not usually at the same time.

[Fella1340]

I think i have all those things, plus the attention span of a six year old:) It's (I'm) a work in progress!

[T.S.Davis]

I have no trouble with attenti.........SQUIRREL!

[bozo586]

terry always gets our attention---he loves smoke!