How to get into FE tunnel the right way.

[lohring]

I feel that rating motors by watts is unhelpful. The limiting factor with the voltages we usually run is current. Many manufacturers rate their motors by maximum current and don't reference the input volts. Most others reference both the maximum current and maximum watts. Since nearly every other component like the connectors, wires, and speed controls is current limited, I feel concentrating on the system's current is important. When the load on the motor changes, the voltage from the lipo battery will remain nearly constant. However, the current will change drastically. Electric motors don't stall from overloading like IC engines, they melt.

Lohring Miller

 

[Tim leyde]

How long is the shaman? I might start a p tunnel, but want to use a hull I already have.

Gary,

A Shaman is 31" long vs a Lynx at 29". Inches don't allways tell the tale as my 32" .45 hull has proven itself as a rough water hull against some 36" boats. Total weight is a better guage. Jay ran a "P" ltd/spec Shaman at the FE Nationals and won heats plus setting the low time on a short 8 lap course. In bigger water on 6 laps like Charleston I preffer the larger boat. Yes a Lynx will be faster but won't carry speeds through the corners and survive water that the Shaman will. My Vision is lighter and faster also but I would take the Shaman every time in a heat race. You might be surprized how little you give up on the big end to get handling. The Shaman also will work as a full "P" but your back to being careful around the course. Everyone thinks their driving skills can handle all the speed after they test and go through corners without any other boats on the course. That line of thinking keeps me racing succesfully.

Mic

Sorry, Mic. You lost me. Are you saying your pick for heat racing a 40 size hull is a Shaman or Vision?

Tim

 

[HTV Boats]

How long is the shaman? I might start a p tunnel, but want to use a hull I already have.

Gary,

A Shaman is 31" long vs a Lynx at 29". Inches don't allways tell the tale as my 32" .45 hull has proven itself as a rough water hull against some 36" boats. Total weight is a better guage. Jay ran a "P" ltd/spec Shaman at the FE Nationals and won heats plus setting the low time on a short 8 lap course. In bigger water on 6 laps like Charleston I preffer the larger boat. Yes a Lynx will be faster but won't carry speeds through the corners and survive water that the Shaman will. My Vision is lighter and faster also but I would take the Shaman every time in a heat race. You might be surprized how little you give up on the big end to get handling. The Shaman also will work as a full "P" but your back to being careful around the course. Everyone thinks their driving skills can handle all the speed after they test and go through corners without any other boats on the course. That line of thinking keeps me racing succesfully.

Mic

Sorry, Mic. You lost me. Are you saying your pick for heat racing a 40 size hull is a Shaman or Vision?

Tim

Tim,

Not at all is the average 40 boat the pick. A Shaman is only 2 inches longer than a Lynx and kind of an inbetween size hull. It works as a 40 boat but really best in the 40 OPC or the can muffler class. They also work with a mod .21 though not many run them there. I take handling over speed every time. The Lynx is a couple faster to the sceen of the accident. I would rather run full throttle than have to feather an overpowered boat. The best drivers can do it and everyone thinks they can manage the speed but they are also the ones you pass 4 to 5 times upside down in a corner. Just cause you can run wide open around a course on perfect water does not mean that's what you race on. As it get stirred up the larger boats have little disadvantage. Just my choice of setup. The "P" spec power is superior to a stock OS and won't outrun a mod on top end but will outpunch both IMO. A lot of people buy a VS-1 and put an FE powertrain on it. I would opt for the TS-3 in a minute. Maybe Grim has an opinion here.

 

[Doug Smock]

We should also work out the amps cause we wanna make sure were not gonna cook the speed control. so we divide kv by votlage to get amps (kv / volts = amps)

2400 / 14.8 = 162 amps

1800 / 14.8 = 121 amps

If I have gotten any of this wrong, someone please chime in and correct me. Mic can add some insight as well. Doug S. you are an FE Guru. Please post some of the calculations you know that will help or correct anything that I got wrong.

/B

Bill you were good to about here. KV and voltage won't give you load. (amps)

Example. The Aquacraft motor is 2030kv and is rated at 7-18.5V and 50 amps continuous, Max surge current 80 amps.(5 sec)

I'm not a FE Guru. A FE Guru is a guy that can push this motor to 90 or 100 amps continuous and not hurt it. :lol:

Doug

 

[HTV Boats]

We should also work out the amps cause we wanna make sure were not gonna cook the speed control. so we divide kv by votlage to get amps (kv / volts = amps)

2400 / 14.8 = 162 amps

1800 / 14.8 = 121 amps

Thats the answer i needed thanks bill

So watt rating only tells you how much the motor should survive

for example if i had lets say a 1000w motor that was 1800kv

and another that is rated at 2000w and also 1800kv

if i put the same prop on for each motor they would both theoritcally

make the same RPM and pull the same amp draw ?

the 1000 watt motor would fail if it was proped the the same as the 2000w ?

Hopefully what i have said is correct and i can move on lol

Greg

Greg,

I am not sure of the correct formula and someone hopefully will chime in. You do have the concept though as a higher watt rating motor will draw more amps allowing it to make more power. Now if the motor can take a larger load the fuse part goes back to the ESC's limits. A large draw motor may smoke the ESC as the motor and battery won't regulate limits. That 1000w motor would fail because the prop load was too much as the ESC allowed enough current to make it fail. Just going to a 2000w motor you will need an ESC that can handle the amperage draw created by the prop not just the motor. Dropping from an M445 to a X438 would decrease the load and heat plus allow a longer run time, but run much less mph. Somewhere in going up in prop and mph you will be within a safe heat range and the next small increase in prop causes the heat to increase exponentially. It is like dropping off a cliff with little warning. Proper balance between components give the best results. There are many combinations that will yield similar results in an open motor and ESC unregulated. "P" spec is an manufactuered and designed system that can be overloaded by weight or prop load. With so many people running this system we have a pretty good handle on what props will work safely. In Open FE we are learning as we go with knowledge like were sharing here.

Mic

 

[rumrunner]

What do you guys think would be the biggest class at the tunnel champs? P spec or p tunnel?

Thanks Shane

 

[Bill Britton]

Mic

i was assuming that the ESC and battery could supply unlimitied amps in what i was saying

Of course that will never be the case.

I plan on using a Turnigy 180 amp ESC as i have 2 of these from hobby King

I was looking at the leopard 4074 2150 kv . Not sure what batterys to get just yet.

looking at puting it on a HTB 290 to start with as i have one here not doing anything

Kris Flynn will be sorting out the lower and adapter for me at some point.

So assuming i have mid range batterys 4s 5000mah @ 30-40c what props should i be able to turn ? i was thinking about the x440 or abc 40x53

Greg

That would make a very hot HTB indeed. What you would have is a .21 size tunnel that is overpowered. Although you would be taming it with the smaller prop. What you described in hardware is basically equivalent to what we are running in .45 size hulls.

 

[Bill Britton]

What do you guys think would be the biggest class at the tunnel champs? P spec or p tunnel?

Thanks Shane

Shane

Probably the p-spec as we will probably run the p-tunnels in open tunnel.

Build one, I dare ya!

 

[Bill Britton]

We should also work out the amps cause we wanna make sure were not gonna cook the speed control. so we divide kv by votlage to get amps (kv / volts = amps)
2400 / 14.8 = 162 amps

1800 / 14.8 = 121 amps

Sorry for the wrong equation. Doug schooled me this afternoon.

The corrected math is here;

watts / volts = amps.

So if the above motors are 2500 the answer would be;

2500/14.8 = 168 amps for both motors

I'm such a noob! B)

 

[Dick Loeb]

P/Limited(spec)

 

[Kris Flynn]

Excellent thread guys, I am glad you have FINALLY caught up and started running FE Outboards!

Cheers

Kris

 

[HTV Boats]

Mic

i was assuming that the ESC and battery could supply unlimitied amps in what i was saying

Of course that will never be the case.

I plan on using a Turnigy 180 amp ESC as i have 2 of these from hobby King

I was looking at the leopard 4074 2150 kv . Not sure what batterys to get just yet.

looking at puting it on a HTB 290 to start with as i have one here not doing anything

Kris Flynn will be sorting out the lower and adapter for me at some point.

So assuming i have mid range batterys 4s 5000mah @ 30-40c what props should i be able to turn ? i was thinking about the x440 or abc 40x53

Greg

That controller should work just fine. The 290 you might find a little overpowered. An X442 or Grimracer 42X55 will be very safe. I would lean twords a GR 42X66 then 45X68 or M445 which we are turning with our spec motors. Above that is a 545 or M447 which may put you over the safe zone. Run 2-3 laps and bring it in and check battery and ESC temps. Increase laps till your comfortable with props not heating things up over say 130 degrees. Above 150 and you are in the twilight zone and will puff something. We are using 5.5 to 6.5 bullets on the battery connections. 6.5mm is better and 8mm you will need a pliars to separate. The 4mm motor connectors are ok and if you want going to 5.5mm is just insurance of a better connection. Post up how things work. We havent used our "false God" GPS in a while but one nice thing here is distance run which you can compare to MAH's used which you will know when you recharge. If you make 1.5 miles and have 25% charge left in the batteries you should be good to go in a heat.

Mic

 

[HOTWATER]

Excellent thread guys, I am glad you have FINALLY caught up and started running FE Outboards!

Cheers

Kris

 

[obrien]

There is a good bit of info in this thread. Keep up the good work Bill and Mic.

 

[HTV Boats]

One thing we did not address here is going to a larger power setup over "P" spec you may run out of battery if you prop up a Full "P" or "Q" tunnel. I have run a 1 mile heat with a P-spec and an Grim Racer 4200ma 4S pack and used about 70-80% capacity. Just over 3000 ma used. Since you don't wan't to get into the low voltage cutoff we kind of recomend 5000ma packs. Since we have not raced in heats yet with a "P" or "Q" we are hoping 5000ma will last without going down in prop. Their are 5400 and 5800 single packs availiable and I have a 5400ma that should be ok. Running larger packs or say two 3000's in parallel giving 6000ma total will be a little harder to fit in a box under the cowl. This and as you store energy the weight goes up. Rule of thumb every 3000ma is about a pound. A 5000ma 4S single pack 1P weighs about 1.4 lbs and is roughly 1 7/8" X 2" X 6" long. Those dimentions vary with manufacturers. Zippy makes an 8000ma 30c that weighs 2.2 lbls and is 1 3/4 wide X almost 3" tall and a bit over 6" long. Physically very large to fit in a box under the cowl.

Do not get too crazy on C rating. You could probably race a 20C in spec but most feel 25-30C is minimum and 40C better. If your running record trials you may want more than that but I have 30C's that I am confident will run heats very well. The higher the C rating the higher the charge and discharge rating is. I charge at 2C with batteries that are rated up to 5C charging. 5000ma at 1C or 5amps takes an hour to charge. at 10 amps - 2C only 30 minutes. I feel lower charge rates are better for battery life though some may argue for higher being better. Since you may only replace 3500ma after a heat charge time at 2C would be about 20 minutes. Some of the cheaper chargers may only charge at 5-6 amps. I have a Hyperion dual charger ($260) That will charge and balance 2 batteries at once at 25 amps each. Will drain your car battery in a hurry so I bring along a marine deep cycle which should run 4-5 boats all day. Some of the FE guys running a lot of boats use small generators that have 12v outputs. I would recomend an inexpensive charger at first then if you are expanding in FE a Hyperion or Triton is a wise move. They will charge nicads nimh Life and lipo's and a few others so good to have in your tool box. Also if you put a set of bullets on your nitro starter a 14.8 -22.2 pack will outpower a lead battery at a small percentage of the weight.

Mic

 

[Tim_Duggan]

We have a Weight limit in Australia on the Packs

Not 100% sure about it but im pretty sure you cant

run 2p. Kris will know more about it.

Yes Greg we do have a weight limit on the pack + wires and connectors in Australia. Most 4S1P 5000mAh packs will be OK. We also have a bit of a gentlemens agreement to run P spec motors with the EA O/B tunnels - UL-1 motor is the way to go. Keeps the racing close and the costs down as 120A ESC's work just fine.

 

[Tim_Duggan]

:lol:

 

[Tim_Duggan]

B)

 

[Bill Britton]

Gonna take the P-tunnel out today and try and get some video.

Ordered the 4074 2200kv Leopard from OSE yesterday. It will probably be better suited for p-tunnel than the 4082.

 

[lohring]

You're confused about series and parallel connections. Connecting 2 - 7.4 volt, 4200 mah packs in series gives 14.8 volts but still only 4200 mah. Connecting them in parallel gives 8400 mah but only 7.4 volts.

Lohring miller