Random question ---

Is there any prop that i can even remotely begin to consider for a 4100kv Outrunner motor that makes about 1100 watts with a 4s 45C lipo??

I want to make a pusher jet out of this F16 i have --- but don't necessarily need a pusher prop -- i can use an APC mounted opposite on the motor.

The rpms would be insane of course -- I can say this much -

I tried it out on the bench with a 7x6 APC E prop ---- Trust me when i say I stood well away and barriered from the bench setup.

It went 128 amps at 1500 watts i wasn't at full throttle for more than a 1/2 second.
I could hear the motor was not liking it at all and pulled it back. 4s 4800mah 45C lipo and 60amp esc rated to 80amp for 10s --- and apparently rated to 128amps for 1/2 second+ because she appears to still be working fine.


The thrust must have been incredible. Anyways --- I'm thinking of trying something like APC E 5x4 or 6x3.

I can say a 4.1x4.1 failed catastrophically at 37amps and 570watts and probably i made it to 75% throttle before failure --- but may or may not have been due to the benched setup coming loose in test --- i don't know if the chicken or the egg failed first. The blades may have gone bye bye causing the whole thing to jar loose and shread further. Or the setup came loose in the bench and blades touched and toast from there. Either way it snapped the 3.17mm turned-down tip of my motor shaft clean off. So now its a straight up 4mm motor shaft --- better this way anyways. i just etched a new E-clip ring in the shaft and it works great again.

But anyways i need a prop to get in the 1100watt max range or even really 950+ would be good enough for the model i want to put it in.

Just that the 4100 KV is so dam high its pretty outrageous i would think for APC prop rpm maximums i have seen on APC's site -- 57000rpms on 4s is what my motor wants to offer... but APC 5inch props 27000max i'm seeing i APC's site.


Also on a 4mm shaft motor --- how much motor shaft can reasonably stick out past the bearing? I have a long shaft of about 1.25 - 1.5 inches sticking out past the bearing -- may need to trim it a tad shorter for safety?

Hi WRX, I have a Sapac MB-1 3200Kv motor in a HET ME-163 and on 4s with a 5x5 APC prop it was putting out about 1100 watts, 76 amps with RPM's at 31,200. Speed at WOT is about 135 to 140mph. I went down to the 4.75 x 4.75 EMP prop and ran up the motor on a 5s pack and got 1776 watts at 98.01 amps with the RPM's at 42,300. I did not fly the ME-163 yet on the 5s pack cause of the high winds we had all week here in PA. I like the EMP props better than the APC props. I think you will need a lower Kv motor to get the numbers you are looking for. Also you are better off with the 4mm shaft at that power for sure.

Keep em flying
raido56/Herb

Originally Posted by raido56

Hi WRX, I have a Sapac MB-1 3200Kv motor in a HET ME-163 and on 4s with a 5x5 APC prop it was putting out about 1100 watts, 76 amps with RPM's at 31,200. Speed at WOT is about 135 to 140mph. I went down to the 4.75 x 4.75 EMP prop and ran up the motor on a 5s pack and got 1776 watts at 98.01 amps with the RPM's at 42,300. I did not fly the ME-163 yet on the 5s pack cause of the high winds we had all week here in PA. I like the EMP props better than the APC props. I think you will need a lower Kv motor to get the numbers you are looking for. Also you are better off with the 4mm shaft at that power for sure.

Keep em flying
raido56/Herb

ok good deal -- thank you for those figures!! After seeing the kind of RPM's the 7x6 could handle -- i'm convinced there must be a prop out there that can take 4100 kv --- if just the 7x6 was less in wattage ---- maybe i'll have to keep it at 80% throttle ---- i know that never makes your ESC happy --- but worth a try. I don't mind a little abject failure in the name of trial & error.

I really think the small prop setup 4.1x4.1 failed only due to loosening in the bench grips --- letting the whole thing jar loose in mid run - causing the failure. So if you got a 5x5 at 1100watts on 4s ---- with a 3200kv motor --- a 5x3 or a 5.5x2 might be a viable option. From what i read, the smaller the prop the higher the SAFE rpm limit should be overall.


Well -- guess i am going to buy an assortment of several and try them all out till i find what works best if at all. Sounds like it could be a fast model overall if i can get it to work.

I'll start at 4.75x4.75 and work my way up. Actually i've even got a few 4.2x2 props ---- but i just don't see how such a small prop can push such a large jet (1050-1100g AUW weight). I feel like the prop should be longer - but less pitch -- maybe 6x3 (thats an inch shorter and 50% of the pitch of the 7x6 i tried out at 1500 watts). So then if it went 2 inches shorter at 5x3 ---- that has got to bring wattage down considerably i would think.

i wasn't bold enough to get close enough to tach the 7x6 prop --- so i don't know what rpms it made. I'm certain the motor could not handle the power so no way did it get to 57000 rpms or probably even close. Maybe it made it out to 35-40k i would speculate at best -- still is mad thrust at those rpms. Prop calc says around 7300grams of thrust at 35k rpms for a 7x6 -- WOW.

ok we'll see how this goes -- ordered a 5.5x2, 5.5x2.5, 6x2, and 6x3.

I also have a 4.2x2 already and i think a 4.75x4.75.

I have to wait for a 4mm prop adapter to show up and build a new mount up as well before i can do more bench testing or get 'er in the model.

Gonna slap this on a BH F-16, scrap the thrust vector unit and fan -- should cut ALOT of weight out of the rear of the jet -- 70mm fan unit was 70g and i think the TV unit is a solid 80g but i'm just guestimating -- haven't removed the TV unit yet.

The full flying stabs on this jet have a TON of throw and can really move her around sharply anyways -- so heck with the TV unit -- it had very little throw and weak servos i found anyways. oh yes less another 20g in servos too! I might really be able to get down to a little over 1000g AUW on this jet --- with a 4800mah LIPO nonetheless!!!

I built a phase 3 f 16 with a hoffman edf motor , uses a apc 4.1x4.1, kv was 4600 i think , on 3 cells its was radaired at 120 mph , was about 650 watts , 4 s was over 1200 watts , never flew i on 4s just bench tested , speed control was too small and at the time didnt have a biger one ....

Thanks Dennis--- sorry i missed thi post from a while back. The prop runs decent with the motor i used at 1075 watts ---- 5.5.x2

Here's the thread -- i will have the jet flying this weekend hopefully -- trying to get some video of the maiden.

http://www.rcgroups.com/forums/showthread.php?t=1539127