John McClean 1 Posted August 27 Share Posted August 27 The KV, konstant velocity, rating of a BL motor is at no-load, no propeller fitted. When the motor is running with a prop the RPM will be lower. I've seen it at 80% or 75%. Any lower and the motor could be over-loaded. Is there a way of knowing the on-load speed when planning a new set-up ? Regards John Quote Link to comment Share on other sites More sharing options...
Shaun Walsh Posted August 27 Share Posted August 27 propCalc 1 Quote Link to comment Share on other sites More sharing options...
Phil Green Posted August 27 Share Posted August 27 a tacho? 1 Quote Link to comment Share on other sites More sharing options...
Andy Gates Posted August 27 Share Posted August 27 Instant answer is no. Software as per Shauns suggestion will give a close prediction, E calc and MotoCalc will do similar. For real term results, a tacho with the exact units in use (motor, battery, ESC & prop) will give an exact answer, but personally I would not get too hung up with RPM. Watts per lbs is more critical but again, using a set up that gives the desired performance is what is required. 1 Quote Link to comment Share on other sites More sharing options...
Chris Walby Posted August 27 Share Posted August 27 How about starting the propeller debate as some stir air/make noise and some actually move air for the same RPM, won't that significantly impact velocity? 1 Quote Link to comment Share on other sites More sharing options...
Dickw Posted August 27 Share Posted August 27 (edited) Being able to predict/plan the rpm as a % of the no-load rpm is useful for aiming for the most efficient or effective use of the power system. Use of a tacho can come later once the system has been created to confirm if you have achieved what you aimed for. I do use software for that purpose when starting from scratch, or you can look for something similar someone has already done and see how that worked out. Dick Edited August 27 by Dickw Quote Link to comment Share on other sites More sharing options...
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