40,000 rpm........what's the problem

[keithbradley]

I'd like to see some links to where people have implied there would be motor failures simply due to rpm. Did I miss that somewhere?

If I didn't imply that earlier, I will now.
I've done a lot of RPM-based testing to failure. The four pole motor design is quite vulnerable to centrifugal force at high RPM. The larger motors are of course at risk at the lowest RPM. I've seen failure points that were sub 38,000rpm on a brand new motor, but also some that held up at much higher RPMs than most would ever believe.

[larryrose11]

If I didn't imply that earlier, I will now.
I've done a lot of RPM-based testing to failure. The four pole motor design is quite vulnerable to centrifugal force at high RPM. The larger motors are of course at risk at the lowest RPM. I've seen failure points that were sub 38,000rpm on a brand new motor, but also some that held up at much higher RPMs than most would ever believe.

Keith, did you instrument the motor for these high RPM tests? Can you share some results and insights?

[Fella1340]

It would be nice to know what motors held up to the high rpm and a few motor wind/kv and voltage combinations that have proven themselves to be good for SAW running. I'm not asking for any deep secrets, just some popular combinations that work well in the 80 plus mph area.:-)

[ray schrauwen]

Lehner's or Neu's with 8mm shafts...??

Ask Jeorg, 140mph on Nimh's:

[properchopper]

Some Unpleasant Truths

OK. I can't hold back any longer and be true to myself although this most likely will genuinely alienate some of you who are recent online friends. I'll take that risk. Some may understand, probably not everyone. Here goes :

First off, the term SAW, until recently referred to Straightline Competition Time Trials. SAW boats were and still are fielded by those immensely dedicated to the enormous time, expense, and sacrifices to use and earn that designation. Using the term SAW to describe an overly aggressive sport setup to zoom in one direction for 2 or three seconds, blowover, break, combust or perform a creeping U-turn and repeat a few times doesn't mean that it's a SAW boat (at least to me and I know of others who would agree) anymore than while equally "technically accurate by definition" a Saigon animal Doctor would, out of respect for those that served, call himself a Vietnam Vet. FWIW when I first started out in FE I too was a zoom-zoom back-and-forth runner and the first and founding member of the ZBS/WTS Club [ZoomBangSplash/What'sThatSmell?]. I soon became bored with that, got into oval racing where your rig wasn't good to go until it could do a mill + six or seven laps on the 1/6 mile course. That's when my learning curve really started to drastically ascend and my builds became rock solid. Even so I've managed to earn nine National titles in SAW Competition, never ever with more than 37Krpm and the last four with only 34K, with several runs over 70mph with a spec 2030KV motor on 4S.

Are you pissed off yet ?

For those that want to go, let's say 80mph or even above, I'll give you a close analogy : It's like Rodeo bull riding ; Everyone stays on right out of the gate ; Few stay on for seven seconds.

I still think that the OP was asking a good and needed question to start this thread and it's fostered some constructive (for the most part) conversation. It does however make me wonder how one can consider, given the extra wear, current consumption, and mechanical stress imposed at major rpm is any better than a well-tuned setup in the lesser range that does basically the same thing preferable. For those that need documented "proof" I can dig out of the vault mega-rpm horror photos from the last two dozen or so SAW Competitions I've been to. But are you "proof seekers" the same people who would ask your skydiving instructor to " document and prove" why skydiving without a parachute isn't a good idea before you jump out? C'mon, really ! It's the laws of physics last time I looked. And the advice of those that've been around FE for decades, ya' know.

Take a deep breath. I'm just an old dog close to completing my 70th trip around the sun this year and can get cranky without my daily cheeseburger. And applications to the ZBS/WTS Club can be had by mailing a self addressed, stamped envelope to :

The South Bay Home For Terminally Bewildered FE Racers
Torrance, California, USA

Tony

[photohoward1]

Yeah Tony! Thank you.

[srislash]

I'm with you Tony, well said. There is a lot to setting up correctly, props(big one here), and balance(everything from shafts to whether it keeps straight and true). Some ground to be gained in all of these but when all are achieved...

[kfxguy]

I'm not pissed myself. I don't really like to refer to my boats as "saw" boats anyway. I don't even know what "saw" really is supposed to stand for anyway and I think saying I have a "saw" boat sounds silly....especially to someone who isn't into rc boats. Whoa! Wait a minute...we are talking about RC boats aren't we? Toys are they not? Really expensive, but still toys. My Co workers think I'm a 37 year old kid for playing with them. Let me tell you, yea I like my boats, I like messing with this stuff, trying new things and above all I enjoy building them more than driving them. I will not, however, get bent out of shape because some people do things differently to arrive at the same result. Some of you guys like to use lower rpm because...what? It had less wear and stress on what? A 4 dollar piece of brass tubing? A 18 dollar flex shaft? A 5 dollar bushing? Even a motor? I blow a motor up....I laugh and go buy another. I blow an esc up, I laugh and go buy another. I sink my boat...we'll I might cry a little (lol) but I'll build another. And guess what, none of its in vain as I'll have learned something. I have respect for all of you guys, your good at what you do, but no one in this world knows everything there is to know about everything. Even toy boats. This what we are doing here is just to pass time in life...it's what we choose to do because it's fun. It's fun building, driving, and burning/blowing stuff up. :)

[Luck as a Constant]

Sent from my iPhone using Tapatalk

[Brushless55]

OK. I can't hold back any longer and be true to myself although this most likely will genuinely alienate some of you who are recent online friends. I'll take that risk. Some may understand, probably not everyone. Here goes :

First off, the term SAW, until recently referred to Straightline Competition Time Trials. SAW boats were and still are fielded by those immensely dedicated to the enormous time, expense, and sacrifices to use and earn that designation. Using the term SAW to describe an overly aggressive sport setup to zoom in one direction for 2 or three seconds, blowover, break, combust or perform a creeping U-turn and repeat a few times doesn't mean that it's a SAW boat (at least to me and I know of others who would agree) anymore than while equally "technically accurate by definition" a Saigon animal Doctor would, out of respect for those that served, call himself a Vietnam Vet. FWIW when I first started out in FE I too was a zoom-zoom back-and-forth runner and the first and founding member of the ZBS/WTS Club [ZoomBangSplash/What'sThatSmell?]. I soon became bored with that, got into oval racing where your rig wasn't good to go until it could do a mill + six or seven laps on the 1/6 mile course. That's when my learning curve really started to drastically ascend and my builds became rock solid. Even so I've managed to earn nine National titles in SAW Competition, never ever with more than 37Krpm and the last four with only 34K, with several runs over 70mph with a spec 2030KV motor on 4S.

Are you pissed off yet ?

For those that want to go, let's say 80mph or even above, I'll give you a close analogy : It's like Rodeo bull riding ; Everyone stays on right out of the gate ; Few stay on for seven seconds.

I still think that the OP was asking a good and needed question to start this thread and it's fostered some constructive (for the most part) conversation. It does however make me wonder how one can consider, given the extra wear, current consumption, and mechanical stress imposed at major rpm is any better than a well-tuned setup in the lesser range that does basically the same thing preferable. For those that need documented "proof" I can dig out of the vault mega-rpm horror photos from the last two dozen or so SAW Competitions I've been to. But are you "proof seekers" the same people who would ask your skydiving instructor to " document and prove" why skydiving without a parachute isn't a good idea before you jump out? C'mon, really ! It's the laws of physics last time I looked. And the advice of those that've been around FE for decades, ya' know.

Take a deep breath. I'm just an old dog close to completing my 70th trip around the sun this year and can get cranky without my daily cheeseburger. And applications to the ZBS/WTS Club can be had by mailing a self addressed, stamped envelope to :

The South Bay Home For Terminally Bewildered FE Racers
Torrance, California, USA

Tony

I wanted to repost this just because its real !
Thank you Tony

[Doug Smock]

It's fun building, driving, and burning/blowing stuff up. :)

This is where you'll have disagreements with those that have spent years promoting Fast Electrics and fast reliable set ups. Not everyone is going to share your enthusiasm when it comes to "burning/blowing stuff up".

Although I dislike the word newbies......

Like Ray mentioned, most of us want FE newbies to have a good first experience with RC Boating. So preventing them from burning stuff up is why we err on the side of conservative recommendations. BTW- Same thing goes for prop recommendations for a given set up. If someone wants a prop recommendation, the first thing I ask is "what's your application".

Fun to me is learning how to take a 48" mono 92+ mph and the equipment doesn't even know it's in the boat.

Glad you're having fun!

Easy Tony, at you're age you don't need to get wound so tight. But as you know, I agree.

[tlandauer]

I wanted to repost this just because its real !
Thank you Tony

Ditto!
I can see the dollar signs goes up faster than my RPM , the high dollar boats I witnessed at the SAW event were truly amazing, I would love to own one, but I would not and could not afford to run one let alone to maintain one or an entire fleet.
I know my place and I am happy to remain at the bottom of the food chain . I respect those who want to push the limit on a regurlar basis and without them we will not be where we are at today.
My point is that each of us has a different agenda and ultimately we reach that goal more or less. It is important, at least on a personal level, that I don't give myself too much grief while reaching there. So probably I will not be that 40,000 RPM guy, but, hey, that's ok!

[properchopper]

Last post and I'll leave the rest to carry on. I don't see a common ground for agreement between the sport zoom-zoom guys and the racers but I will stand on the concept that either group has the absolute right to do whatever sets their toes to tappin'. If a sport boater wants to go high rpm and laugh off the breakage that's fine with me. I, on the other hand have, for just one particular event in the last seven running years saved up (with my four part-time jobs) to build and equip 6 or 7 boats for as many classes, endured a five day 900 mile road trip, spent upwards of a thousand hard earned dollars each time to race with my friends. Plus the yearly D19 race schedule (fewer classes, thankfully except for when SoCal put on the FE Nat's). My boats HAVE to go the distance, not blow up and float to the middle of the course SO I rig them in such a way that they'll finish using principles that allow finishing. That's my POV and I'm not expecting anyone to agree NOR have I yet, as has been suggested, am or have ever met anyone who claims to know everything to know about everything. I have however discovered what, for my own personal purposes, works, and what does not and I'll concede that I don't have the right or, at least for now after reading some posts here, the inclination to continue to give my side of the story.

Happy boating

Tony

Oh by the way (to quote the OP's words from an above post), you might want to look into the fact that someone in the link below may be using your screen name :

" I don't really like to refer to my boats as "saw" boats anyway. I don't even know what "saw" really is supposed to stand for anyway and I think saying I have a "saw" boat sounds silly..."

http://forums.offshoreelectrics.com/...first-saw-boat

Q.E.D.

[properchopper]

Easy Tony, at you're age you don't need to get wound so tight. But as you know, I agree.

Thank you Sir I try not to get wound up so tight; last time I did I captured a small town outside of Khe Sanh

[kfxguy]

Man I didn't mean to ruffle any Feathers. Your obviously more into this stuff than me. I'm not competing like you are so I guess ultimate reliability is not my major concern. Having fun is. I was originally just wondering what's the worst outcome or should I say more common bad outcome of running high rpm. Let me elaborate on something. This is probably one of the cheapest hobbies I've had so far. So if I blow a 100 or 150 motor up....it's laughable to ME. When I was racing cars and atv's when I had an engine let go...I was used to spending lots more money. So don't take anything I said the wrong way. Everyone has their own way of doing things. Like I said I respect you guys and what you do. It's pretty amazing....I've seen some of you guys stuff really fly. This thread is good at arming people with additional info so don't get upset man. :)