New Rc motor,Tadpole trike build input needed

[illchilla09]

First off let me say I am new to the electric bike builds.I am currently building a tadpole trike that I plan on converting to electric.I work in a machine shop so I can make my own custom parts luckily.I planned on using a rc setup and just wanted to get some input on weather or not you more experienced guys think it will work.My goal is within reason I think.I am reaching for 30mph with fair acceleration.I would like to get 10 miles per charge.My idea was to have a direct drive or is it called a single stage drive?I planned on attaching a freewheel bmx sprocket to the motor with a small tooth count and using a disk brake hub to sprocket adapter in the rear to mount a large sprocket.I have no idea about the tooth count for the sprockets yet.I am going to use the Turnigy 80-100 130kv motor from hobby city with servo tester.Anyone know if this sort of system will even work?Any suggestions on the tooth count for the front and rear sprockets?I was going to run this on a 36v lipo battery pack I can build.I think it will work but my concern is the initial amp spike at startup burning up the esc.I still haven't picked out an esc either.Thanks for any and all input.I will upload pics when I figure out how to shrink them.

 

[recumpence]

You definately need a Castle controller. I would go with a HV160.

You will need a two stage reduction, motor to jackshaft, jackshaft to wheel. Otherwise the motor will run way to slowly and far out of its efficiency range. Other than that, it should run fine.

Matt

 

[Thud]

Hello & welcome to the forum,
Single stage reduction is very doable but in reality I would recomend a primary reduction in the drive line. you will have a very difficult time getting the reduction you will require with bicycle chain in a single reduction. Lets do the math:

whats your rear wheel size? 20" 24" 26" 27"
30mph=
20"=505 wheel rpm
24"=420 wrpm
26"=388wrpm

130 kv @36v =4680 we'll use 75% of that as the world is not perfect & your trike will weigh something....3500rpms

20" drive will require 6.9-1 gear down....smalest conventional freewheel is 16t. But as a machinest you will make a 30mm bmx compatible one & use a 14t.
sooo thats a 97 tooth rear sprocket essentialy rim diameter of a 20" wheel with .5" pitch chain 15.438 pd. The ratios get bigger from there. I have made single stage reductions & have one running now on a 24" wheel with a 131 tooth #35 driven with a 10 tooth.
a simple jack shaft with #25 drive chain will sep you into a range way more component friendly. oops typed too long...Matt beat me to the send button.

I am not a sales man, but if your going to attemp to use an Model Airplane controller spend the money on a castle creations unit. Add at least 1 Low esr capacitor to tame riple currents & set it up to run at full throttle for 90% of the time. even if it means gearing for a slower top speed....intermediate throttle settings are a death sentance to any of these micro sized controllers. I have not blown an "rc" controller yet following this recipie (i thought i had on 2 ocasions but it was motor failures on both occasions)

 

[illchilla09]

Thanks alot for the fast responses.I am going to be using a 24" rear wheel and I did find 10 tooth bmx freewheel gears on ebay it that helps any.I was thinking on using the CC 160 hv.Think I could get away with a smaller esc like the CC120 HV?If I was going to use a 10 tooth front sprocket,what size rear sprocket should I try first?Thanks again.

 

[Jeremy Harris]

Thanks alot for the fast responses.I am going to be using a 24" rear wheel and I did find 10 tooth bmx freewheel gears on ebay it that helps any.I was thinking on using the CC 160 hv.Think I could get away with a smaller esc like the CC120 HV?If I was going to use a 10 tooth front sprocket,what size rear sprocket should I try first?Thanks again.

I'll answer, as Thud's probably in bed by now (the joys of this forum being global means we're all out of time sync with each other!).

For 30mph, with a 130Kv motor (at 75%, 36V) driving a 24" wheel with a 10t motor sprocket you'll need around an 83t rear sprocket. This is pretty big - you'll probably have a challenge finding one that big that'll take standard 1/2" pitch bike chain (the sprocket would be around 13.3" in diameter).

You're better off with either a double stage reduction or, perhaps, switching to smaller pitch chain. Although smaller pitch chain would bring the rear sprocket diameter down, you then have to look at fitting some sort of one-way clutch somewhere in the drive line to act as a freewheel. This can (and has) been done OK using roller clutches, but needs some machine work.

Jeremy

 

[Hillhater]

Why dont you consider running 24v instead. ? That would make your gearing reduction easier.

 

[illchilla09]

Hi,I didn't realize running a lower voltage would make the reduction easier.I'm new to all this e bike building.I was actually going to up the voltage to 48v.I was thinking that if I threw more power at it then I could use a smaller rear sprocket.I have been reading alot here at Endless Sphere and am slowly learning though.What a great forum this is.Thanks

 

[illchilla09]

I wonder if I would be better off just using a 48v, 1000 watt brushless scooter motor?Would that eliminate my need for a two stage drive and still give me good acceleration and speed?

 

[illchilla09]

Some pics of my progress so far.

 

[drifter]

I fitted a cyclone kit to my kmx and it was very easy to do and works well.

 

[Samba]

Cyclone has a different setup for recumbents that uses a double freewheel right on the motor shaft. It could take care of all the chain routing if it can be put in just the right place. One run of chain from the crank to the motor, and a seperate run from the motor to the rear wheel. It seems the simplest - if you have room somewhere between the crank and the wheel - and these trikes do. Their other configurations use modified cranks - which aren't required in the double freewheel configuration.

If you increase the voltage on that turnigy motor from 36 to 48 then it wants to turn 33% faster. That 130kv means it likes to turn 130 RPM for each volt.
Lowering the voltage reduces that speed and the power - but its a 6500 watt motor - about 8.5 HP. Using a lower voltage still leaves plenty of power and gives a more manageable speed.

You would need over 100 amps of power from your batteries. Thats quite a lot of drain - it will require quite a special battery. If you take the same battery cells - but configure them for 24v instead of 48 - you have twice as many cells in parallel which makes providing that level of current easier.

If you go through with it - you would have a trike where the motor is quite efficient for travelling at 30MPH. The motor is only efficient over about 1/3 of its range of RPM speeds, so it may still be happy at 20 MPH. But anytime you are slower than 20mph the motor will be turning at inefficient speeds. Inefficient means that its still consuming lots of power, but converting it into heat instead of motion - so it will heat up a lot when you aren't going fast. Too hot, and it dies.

If you look at the cyclone setups, the motor is powering the wheel thru the regular bicycle chain and gears. The motor can run at efficient speeds whether you are going 10MPH or 30MPH just by choosing a different gear. This needs a whole lot less than 8.5 HP - they range from about 1/2HP to 2HP. It also means less than half the peak current draw which lets you choose from a bigger range of batteries - including bigger, cheaper, safer and longer lasting batteries.

You can do the same with RC motors and speed controls - with some reduction gearing - there are a lot of them in this forum. But I'd seriously consider feeding it thru the bikes shiftable gears. If you plan for a somewhat smaller motor, then you get a wider selection of motors, speed controls, batteries that can handle them. You pay less of a premium price if you don't plan to use the biggest, baddest, newest, least available, state-of-the-art parts.

Nice looking frame - seems like you have quite a bit of space in the rear fork ahead of the wheel. Good place for heavy stuff like a motor as its very near the center of gravity. A drive placed between those 2 chainstays could have good support on both sides.

 

[jmygann]

Mount like this .... ?

but what are the motor options ? Cyclone RC ? Elation ? Hub ? Power pack ?

 

[spinningmagnets]

Bubbas build 5 might have some useful info for you, also Mud2005's build:

http://endless-sphere.com/forums/viewtopic.php?f=28&t=20245
http://endless-sphere.com/forums/viewtopic.php?f=28&t=14734

The motors kV is how many RPMs you'll get (unloaded) per volt applied. The higher voltage you hope for will make the motor try to go a higher speed than 30-MPH with a single-stage. That would end up with you using part-throttle for extended times, which is VERY hard on the sensorless RC-controllers.

Adding a jackshaft and another stage of reduction would put your top-speed at a much better place for available (and low) motor-kVs, plus it makes finding pulleys/sprockets in reasonable sizes easier (rather than ordering expensive custom units)

 

[illchilla09]

Hello to all and thanks for all your input on my trike build.I started to purchase items for my trike.I decided to go with the jackshaft reduction system as suggested.I purchased a motor (budget).It is a #SK-6374-170/7870 TGY AerodriveXp SK Series 63-74 170Kv / 3250W.I plan on running this on 36 volt lipo batteries.I skimped a little on the motor so I could buy a good speed controller.I am going to get the Castle Creations HV 160.Do you think the 120 amp version would be enough for this motor and battery setup?I was leaning toward a left side belt drive setup to power the bike.I want the motor drive setup and the pedaling setup completely seperate from each other.I would like the bike to do 30-35 mph.I have a disk brake hub sprocket adapter that I was going to mount my final drive pulley to.So what we have now is a 170 kv motor,36 volts of battery power and a 24" rear wheel with a final speed between 30-35mph.Can anyone tell me what size pulleys to buy?I will need 4.One for the motor,one for the motor side of the jackshaft,one for the other side of the jackshaft and finally one for the rear wheel.Would a 1/2 inch belt be strong enough for this setup?Any and all help will be greatly appreciated and I am going to continue searching and reading here in the forums.Thanks

 

[Samba]

What size is your disk brake adapter? That puts a lower limit on the size of the rear pulley.

Why not use a sprocket on it and on the final output of the jackshaft?

 

[illchilla09]

Hi,the outer diameter is 3 1/2 inches on the adapter.I work in a machine shop and was just going to drill a mounting hole pattern on the pulley to bolt it on there.Would that work?I wanted to use belts because I just thought it would be quieter.

 

[Thud]

Hello again Ic.

Per your pm request I ran some numbers for you.
my 24" wheels all have 2.4" tires on them & actual dia.=about 25" for 35mph you need a wheel rpm of 474.
Assuming 10 cels of lipo (37v nominal..41v hot off the charger, but we'll use nominal for out calcs.)
No load rpm at listed KV 170 will be 6290....I typicly use 85% of that for gearing calculation=5347rpms
5347/474= 11.3 total reduction required for 35mph top speed.

Here are a few facts: Your actual no load rpms are going to be more as castle controllers advance the timing while in operation to maximise power output.(this is a good thing)

personaly, I think gates drive belts gt2s are great.......But I am a real cheapskate & HDT or GT2 are ex$$pen$ive. & unless your using realtivly large pulleys they tend to jump teeth in primary reduction applications. I have gone exclusivly to HD#25 drive chain for primary reduction. it never skips & is available for peanuts. keep your small sprocket over 16 teeth & it is also very quiet.
https://www.surpluscenter.com/sort.asp?catname=powerTrans&keyword=PH25
look around there & you will be happy. for final drive the most cost effective & easy to aquire chain is #35 drive. (again heavy duty) I buy gokart sprockets off e-bay for the nice anodized racing look & drive sprockets from the previous link. You can buy new masterlinks for #35 at any home depot, menards, ace hardware. adapters are easy to fab & attach in left or right hand drive senarios. (there is a photo journal in my 1st build thread bmx thread making an adapter with hand tools)

any who---to recap a gearin senario, we want a 5.25-1 final reduction=12t driving a 63t & a primary reduction of 2.2ish
i like a 16t driving a 35t.=2.18 reduction 2.18 x 5.25=11.44 total reduction (close enough).

Now for my standard warning regarding an rc set up: if your not going to be driving your set up at 90% of max speed 100% of the time, I recomend gearing lower. 20-22mph max. I am no saftey weenie....its just a starting point to safely (for the equipment) evaluate your system. Even the best Controller is playing russian roullet' if operating under these loads at less than full throttle. If this is your 1st electric build, I strongly recomend initialy seting up with a 15-1 overall reduction set up. You can gradually step up from there & learn as you go while reading your graphs from the CC data logging software. Its very easy to upgrage your set ups for more performance....better than to be disapointed with blown controllers & skipping belts.
the ultimate solution would be to download a set of 2-speed transmision plans & build one for your trike. It will give you the best of both worlds.
I assume you know about adding extra capactors to your controllers?
hope this helps. i am sure i forgot some things so ask away & some one will get you on the right path. you can trust the advice of most here, Especialy Recumpence, he was the pioneer on most of what you are attempting.

 

[jmygann]

assuming a 24" wheel ......50 volt motor - Kv 116 ...30 amps - 1500 watts ... desired speed 30mph .... motor - 16 tooth ...#35 chain

direct drive ... How many teeth on drive wheel ??

 

[Samba]

assuming a 24" wheel ......50 volt motor - Kv 116 ...30 amps - 1500 watts ... desired speed 30mph .... motor - 16 tooth ...#35 chain

direct drive ... How many teeth on drive wheel ??

24" wheel = 420 rpm for 30mph
116kv * 50 volts = 5800 rpm
under load - about 85% of that = 4930 rpm
4930/420 = desired ratio = 11.74:1
11.74 * 16tooth on motor sprocket = 188 teeth on drive sprocket.
#35 chain = 3/8 pitch 188 teeth * 3/8 = 70.5" circumference
circumference/PI = diameter = 22.44" diameter drive sprocket.

You need smaller chain like #25 and/or a smaller motor sprocket and/or a lower voltage.

 

[jmygann]

assuming a 24" wheel ......50 volt motor - Kv 116 ...30 amps - 1500 watts ... desired speed 30mph .... motor - 16 tooth ...#35 chain

direct drive ... How many teeth on drive wheel ??

24" wheel = 420 rpm for 30mph
116kv * 50 volts = 5800 rpm
under load - about 85% of that = 4930 rpm
4930/420 = desired ratio = 11.74:1
11.74 * 16tooth on motor sprocket = 188 teeth on drive sprocket.
#35 chain = 3/8 pitch 188 teeth * 3/8 = 70.5" circumference
circumference/PI = diameter = 22.44" diameter drive sprocket.

You need smaller chain like #25 and/or a smaller motor sprocket and/or a lower voltage.

Or I need to use a 20" wheel and shoot for 20mph , but I still want a motor that will be in its most efficient rpm at cruising speed

I think these formulas are correct

Tire diameter = mph x gear ratio x 336/Rpm


Gear ratio = rpm x tire diameter/Mph x 336


Mph = rpm x tire diameter/Gear ratio x 336


Rpm = mph x gear ratio x 336/Tire diameter

* Find the rated RPM of your motor (run it at half the rated RPM)
* Decide how fast you want the bike to go
* How big are your tires? What's the RPM of your wheel at your desired riding speed?
* What's the ratio between the motor RPM and wheel RPM? that's your gear ratio!

http://www.900mpg.org/electric_building.php

http://endless-sphere.com/forums/viewtopic.php?f=28&t=16114