Best RC motor for lightweight utility bike build

Discussions related to motors other than hub motors.
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liontail   100 mW

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Best RC motor for lightweight utility bike build

Post by liontail » Jan 17 2015 1:42pm

Hey all,

I’m leading a team of mechanical engineering students building an ebike for a senior capstone project. I live in the pacific northwest (USA), and a recent survey found the top 5 barriers to bicycling in this area are:

1) The weather
2) Places I need to go are too far
3) The hilly terrain
4) I don’t feel safe
5) It’s difficult to carry things on my bike

We’re building a bike that I hope will address all of these issues: an electric-assist cargo bike with a rain cover and a full light system, complete with turn signals and brake lights. We’re going to design, perform FEA, and build our own carbon frame for it. I’m excited!

My biggest question is about the motor, and that’s why I’m posting today. We’re trying to stay at or below 40 lb (18 kgs) max weight, so we’ve narrowed down the motor to 2 options:

1) A small rear hub motor, likely the Cute Q100C.
2) A little (1-2 lb) RC motor geared down and assisting the human drivetrain.

These are both very lightweight and have the potential to meet our power requirements, which are:

“Can assist a total bike+rider+cargo bike weight of 350 lbs up a 10% grade at 6+ mph with 150 watts or less of human input for at least 60 seconds.”

I played with Grin’s ebike simulator (god I love that Justin et all put that together!), and it turns out that in theory the Cute motor can do it.

That said, I love the idea of getting 70%+ efficiency at any speed, and so I’m drawn to a mid-drive (driving bicycle's gears) system with an RC motor. Plus, we’re MEs, and so we’re not scared of gear reductions! But we know nothing about RC motors and controllers. I've spent a few hours sifting through this forum, and so I now understand the basics – what ESC, outrunner v inrunner, and kv mean - but I don't know enough to choose a motor. And most of the threads here are about higher-power setups.

So here’s my question:

What RC motor would you suggest we use to achieve our design goal, written above in quotations?

Why?

And what controller/battery would you pair with it? Is it possible to use a standard ebike controller, and so use standard ebike controls?

We need to decide soon, so your input is HUGELY appreciated! Thank you!

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Re: Best RC motor for lightweight utility bike build

Post by mwkeefer » Jan 17 2015 2:23pm

Were it me, I'd get a v4 Recumpence reduction and mount a minimum 3210 Astro Flight motor. That should do it fine, cute motors are not cute :)

Also hub motors make changing flats difficult.

-Mike
Regards,
Mike

{My Rides]
2010 Dahon Jack - GNG v1 - LYEN 6FET - 20/40A - 18S2P10AH - Nom:66.6v,1332w
2004 Hard Rock Pro Disc - Recumpence ms eDrive v4 - Astro 3220 4T - 12S2P16AH - HV110 - Left Side Drive - Gearing: 38mph
Nominal Peak Power @ 60 seconds: 5328 watts - Maximum Power: 49.8v, 120A, 5872w
2010 Downtube 8FH - Stock GNG v1 Stock Controller - EB809XC - 12-16S
2012 Downtube Nova 7spd - Stock GNG v2 - 12S2P10AH - EB809 - 12S-16S - 20A/30A,Nom VCC: 44.4, 888w

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Re: Best RC motor for lightweight utility bike build

Post by amberwolf » Jan 18 2015 3:34am

I suggest looking around at all the various middrive RC motor builds and seeing what they picked and *why*, including the ones for racing by Thud and others.

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Re: Best RC motor for lightweight utility bike build

Post by ErnestoA » Jan 18 2015 4:15am

Having spent a lot on my last mid drive build, I learned a lot of lessons. The two biggest ones were that I don't need near as much power as I thought, and that factory designed systems produced in big quantities are much cheaper and easier to put together a reliable system with.

My next build is a cargo trike and I'll be using this for a motor, controller, battery, and charger setup: http://www.homedepot.com/p/Ryobi-14-in- ... /204589654 I might get a few extra batteries.

It will put out roughly 66 amps at 38 volts for at least a minute and will run until the battery dies at 35A. I'll be going through the gears this time too, which is a huge plus for smaller motor setups. Pretty good deal for $200 and it's all packaged very nicely already.

Sounds like you have a fun project there. It will be interesting to see if you can meet your weight goal. I'm shooting for under 250 lbs with my next build. lol

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Re: Best RC motor for lightweight utility bike build

Post by gogo » Jan 18 2015 12:48pm

ErnestoA wrote:Having spent a lot on my last mid drive build, I learned a lot of lessons. The two biggest ones were that I don't need near as much power as I thought, and that factory designed systems produced in big quantities are much cheaper and easier to put together a reliable system with.

My next build is a cargo trike and I'll be using this for a motor, controller, battery, and charger setup: http://www.homedepot.com/p/Ryobi-14-in- ... /204589654 I might get a few extra batteries.

It will put out roughly 66 amps at 38 volts for at least a minute and will run until the battery dies at 35A. I'll be going through the gears this time too, which is a huge plus for smaller motor setups. Pretty good deal for $200 and it's all packaged very nicely already.

Sounds like you have a fun project there. It will be interesting to see if you can meet your weight goal. I'm shooting for under 250 lbs with my next build. lol
That's very interesting ErnestoA. I'm a big fan of engineered systems and had only seen a hammerdrill in the brushless category last time I looked. This Ryobi could become a very popular repurpose system.
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Re: Best RC motor for lightweight utility bike build

Post by Hillhater » Jan 18 2015 10:24pm

ErnestoA wrote:
My next build is a cargo trike and I'll be using this for a motor, controller, battery, and charger setup: http://www.homedepot.com/p/Ryobi-14-in- ... /204589654 I might get a few extra batteries.

It will put out roughly 66 amps at 38 volts for at least a minute and will run until the battery dies at 35A. I'll be going through the gears this time too, which is a huge plus for smaller motor setups. Pretty good deal for $200 and it's all packaged very nicely already.
I can see the attraction of getting all the components in one package , locally, but that battery is only 1.5 Ahr (60Whr total), and as such is unlikely to last more than 5-6 miles at best, and I would be amazed it it can offer even 20amps continuously, let alone 35 !
Even the optional bigger 2.4Ahr battery will struggle to deliver those figures.
But in reality, you will only really need 5-10 Amps to provide the 200-250 W required for usefull assistance.
This forum owes its existence to Justin of ebikes.ca

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Re: Best RC motor for lightweight utility bike build

Post by ErnestoA » Jan 19 2015 3:41am

I should have said that the motor will "handle" 60+a @ 38v for at least a minute and will chug along at 35a continuously. I used three 12v 200ah lead acids for power and an old generator head running two 1500w electric heaters at different power settings as a load and measured amps with a true rms dc ammeter.

I haven't tested the factory battery performance yet but am sure that a few of them combined with the solar on the roof will get me wherever I need to go and be faster and easier than walking, which is my only alternative option. I do know that the 60wh battery when used as a saw, will saw continuously at pretty heavy loads, 200-300w, for about 15 minutes which should get me up a hill or two.

Reliability and capability are way higher on the priority list than efficiency, speed, and range on this build. If I run out of battery and sun, it's time to either pedal, or pull over, set up camp, and make dinner. lol The fan cooled, high quality outrunner, 12 fet, throttle, battery, charger, and warranty are definitely worth $200 though.

Reducing 12k rpm down to bike wheel speeds definitely isn't the most efficient way to go about things though. I'd re-terminate the windings to wye but I want to be able to unbolt the saw body from the reduction, pull the drive wheel off the motor shaft, and easily reassemble the saw so I can still use it as a saw too.

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Re: Best RC motor for lightweight utility bike build

Post by amberwolf » Jan 19 2015 11:15am

ErnestoA wrote: true rms dc ammeter.
In case it matters, "true RMS" refers to an AC measurement, rather than DC. ;)

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Re: Best RC motor for lightweight utility bike build

Post by Hillhater » Jan 19 2015 7:08pm

ErnestoA wrote:

I haven't tested the factory battery performance yet but am sure that a few of them combined with the solar on the roof will get me wherever I need to go and be faster and easier than walking, which is my only alternative option. I do know that the 60wh battery when used as a saw, will saw continuously at pretty heavy loads, 200-300w, for about 15 minutes which should get me up a hill or two.
.
A saw..especially a "domestic" version like this , will never actually be used continuously for 15 min, or even much more than I min at a time. So the battery will get a lot of recovery periods
But, on a bike, a solid 10-15 min hill is very likely, and that battery will not last that long !
It's simple.. It's a 60Whr pack at maximum, so you cannot expect to get much more than 50W useable from it.
At 300W assist ( which is not very much !) .. So you would have 10 mins assist !
Even with the "high capacity" .. (2.6 Ahr) .. Optional pack, 15 mins would be about the max.
I would confirm the cost of extra battery packs before I committed to that system. ($129 ?)
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Re: Best RC motor for lightweight utility bike build

Post by liontail » Jan 19 2015 8:14pm

Ok, reorienting back to my original question... :)
mwkeefer wrote:Were it me, I'd get a v4 Recumpence reduction and mount a minimum 3210 Astro Flight motor.
I think that we can figure out the gear reduction ourselves - we have full access to a pretty incredible student machine shop - but the Astro 32xx does seem to be a favorite around here. I understand that it's customizable, sealed, and made in the USA and everything, but is it really $400 better than, say, a Turnigy from HobbyKing?
amberwolf wrote:I suggest looking around at all the various middrive RC motor builds and seeing what they picked and *why*, including the ones for racing by Thud and others.
I've been looking, and have found very few if any posts that explicitly detail why they chose the particular motor that they did.

I'll be able to reduce this down to the bike's drivetrain so that it's rotating at about 2000 rpm. Would one of the larger, lower kV outrunners from HobbyKing give good performance at this speed? Like this one?

http://www.hobbyking.com/hobbyking/stor ... Motor.html

I guess one of my questions is about how efficient these little motors are when they're operating below their kV (unloaded) rating.

Thanks for the help so far!

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Re: Best RC motor for lightweight utility bike build

Post by liontail » Jan 21 2015 2:40pm

It may be helpful to give a little more information - it would be great to run this motor at 36V to pair with standard ebike batteries (we're eyeing the AllCell Summit). So that's 36V @ 2000 rpm... either of those numbers can change if there aren't any smallish (<2.5 lbs) BLDC outrunner motors that can run at that speed & voltage efficiently.

Astroflight recommended I either increase the RPMs considerably and use a 3205, or decrease the voltage to at least 24V (and preferably 18V) and use a 3210.

I guess my issue is that I don't know how to get from a given motor, controller, rpm & voltage to efficiency, and I'm concerned that I'll source a motor that seems right but doesn't perform well at all. The online calculators all seem to be for model airplanes... is there a simple formula that you can point me to that will get me the efficiency (mechanical power out/electrical power in) of a given setup at a given rpm?

More likely than not we're going to have to develop our own Arduino board to do the ebike controls, so whether we use an RC ESC or standard ebike controller doesn't much matter - it's more about whatever powers the bike best.

So, does anyone have a motor/controller combination for these specifications, or a good resource to point me in the right direction?

Thanks! Don't want to have to resort to a Cute Q100C... :)

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Re: Best RC motor for lightweight utility bike build

Post by gwhy! » Jan 22 2015 10:10am

liontail wrote:
mwkeefer wrote:Were it me, I'd get a v4 Recumpence reduction and mount a minimum 3210 Astro Flight motor.
I think that we can figure out the gear reduction ourselves - we have full access to a pretty incredible student machine shop - but the Astro 32xx does seem to be a favorite around here. I understand that it's customizable, sealed, and made in the USA and everything, but is it really $400 better than, say, a Turnigy from HobbyKing?


I'll be able to reduce this down to the bike's drivetrain so that it's rotating at about 2000 rpm. Would one of the larger, lower kV outrunners from HobbyKing give good performance at this speed? Like this one?

http://www.hobbyking.com/hobbyking/stor ... Motor.html

I guess one of my questions is about how efficient these little motors are when they're operating below their kV (unloaded) rating.

Thanks for the help so far!
your answer to the astro question is probably no,, the only problem with that is that hobbyking do not sell a inrunner of that physical size.

the small outrunners i.e the 6374's are actually a very good motor but quality is not constant between manufactures.. I have not use the new design of the aerodrive 6374 so am unable to comment on that particular motor but I have used many ( approx 8 of them ) of the older design sk6374's 180kv and 170kv and found them to be very good for efficiency and reliability and you can pick them up for around than $60.

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Re: Best RC motor for lightweight utility bike build

Post by sculptingman » Jan 22 2015 11:56am

Do not even consider any motor other than a Bottom Bracket motor.

First of all... No hub motor works for crap on hilly terrain. They overheat, because they are under direct load, and lose efficiency. BB motors run power Thru the gearing on the rear wheel... Like your car does thru it's transmission... The result is greater control over motor loading... And as far as engineering... The ability to define speed/torque profile Thru gear selection alone.
A 350 watt BB drive performs better than a 500 watt geared hub motor. Without overheating on long uphill runs.

Next...BB motors put the weight lower... Which makes for better handling.

There are several BB drives out there with different power profiles. For hilly terrain, I would recommend the 750 watt Bafang. With that motor, I can tool up 20% grades under throttle alone in 1st or 2nd. Even with a 185 lbs of me, and 50 lbs of groceries in the panniers.

Lastly... Weight becomes pretty transparent on a well balanced bike. I can not even feel the 50 lbs of groceries in the panniers as I climb the 524 vertical feet back from the store. Where it does matter is in being able to lift the bike up a flight of stairs... Or on those rare occasions when you run out of power.

I put a Bafang 750 on a Spot Brand Ajax with a 48v 11ah battery... It weighed in at 40 lbs. Then I added a rack, twin leg kickstand, and brooks heavier fully sprung Flyer saddle, as well as larger ergonomic grips... That brought it up to 43.5 lbs.

Thing is... The ordinary bicycle is already the most efficient moving machine on earth. It's already maximized in terms of being designed for lightest possible weight with sufficient strength for power originating at the BB crank. All available components are optimized for the loads produced by power at the crank.
The gearing systems available are ALREADY designed to make the loading on the power source ( the rider's legs ) as constant as possible thru a very limited range of available power and revolutions.

All a well engineered electric drive needs to do is increase the power of the rider...at the crank... Thus, the only drive that allows you to retain 100 years of innovation in efficiency and weight is a BB drive.

Focusing engineering innovation in making a BB drive that is lighter, and makes more efficient use of power...would net the greatest impact per dollar in terms of eBike weight and performance.

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Re: Best RC motor for lightweight utility bike build

Post by sculptingman » Jan 22 2015 12:08pm

PS... My comments reflect the opinions of a person who has spent 35 years working in product development and design.

Take a look at the Optibike 29er... A steel framed Ebike that weights 39 lbs.

It has a unique BB drive with an optibike designed and made motor WITH batteries incorporated inside the motor housing itself... To keep weight as low and centered as possible.

It's fugly... But proves what can be done with customized motor engineering.

A better 'designed' motor in terms of appearence... Mated to, say, an aluminum hydroformed frame that could offer larger and variable tubing profiles that would make the bulky BB motor less visually apparent.. Would be far better looking and come in at comparable weight.

Would also love to see a bike that will lock up the crank if the owner's smartphone is not within a foot or two...running an app that can Map the route that makes best use of available battery capacity in terms of terrain.

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Re: Best RC motor for lightweight utility bike build

Post by liontail » Jan 22 2015 3:21pm

Hey all,

Thanks for the responses. Since we're in a time crunch on this project, and I still don't have confidence that I'll be able to do a good RC drive, I've decided to abandon an RC mid-drive in favor of a hub motor.

But... will that hub motor actually be mounted as a hub? We'll see! Further discussion in another thread.

:)

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Re: Best RC motor for lightweight utility bike build

Post by amberwolf » Jan 23 2015 1:17am

To avoid repeating all or part of this discussion, you might want to just use this thread for the build and retitle it. ;)

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Re: Best RC motor for lightweight utility bike build

Post by ErnestoA » Jan 24 2015 5:53am

Unless your max weight spec of 40 lbs was the max weight of the motor and not the entire bike, you won't meet your weight goals with any hub motor that's available today.

The motor I recommended above will definitely do what you want to do, very reliably put out up to 2kw and only weigh a few lbs, and can't be beat as far as value, price, and build quality/qc, and availability goes. Can you get any other motor, controller, or battery at your local home depot or hardware store? Having spent close to $2k on a 3220, recumpence drive, hv160, and crappy hobbyking batteries, only to find out that I very rarely was even in conditions that made pulling more than 2kw possible on a bike and would have rather had much less power and gears instead, I really wish I'd pursued the chainsaw option in the first place.

Building reduction drives is easy. Simple get the math right, make sure everything aligns properly, and allow for a little slip to prevent shock loading.
Friction drives are easy for the first stage and belt drive parts can be had for next to nothing at your local junk yard. Subaru's and hondas use 8mm pitch polychain gt belts and pulleys in their timing arrangements. 5mm htd stuff is used in some motorcycle timing setups, as is 219 chain. The parts can be easily turned down and lightened.

On my build, I'll be using a molded 1" diameter epoxy/grit driver wheel attached to the motor shaft, friction driving a 16" diameter 3/4 plywood driven wheel. The driven wheel will contain a csk25 that will be attached to a 22t 8mm pitch toothed belt pulley. A 12mm wide belt will then go to a 63t pulley mounted on a jackshaft that combines with the pedal power, which is geared 63t at the 2 spd crank and 22t at the combiner shaft. A CSK25 will be used as a freewheels at the combiner shaft as well to keep the pedals from back spinning. Both are then geared back down 22/63 into the mid drive N360 cvp hub, allowing it to spin twice as fast as it would if mounted in the rear wheel, reducing the torque it sees by 1/2. Then it goes through one more 22/63 stage to the rear wheel. This matches pedal power/speed with motor speed, reduces the load on the transmission, and is all done with under 15 lbs of drive train(not including batteries), which is less than a hub motor weighs and gives the pedals a 720% gear range and the electric drive a 360% gear range. Hub motors are not as capable per pound for hills and big loads unless they're put in tiny wheels, giving you extremely low top speeds.

Amberwolf,
I stated that the meter was true rms just to point out that it's not a POS $30 meter. It's a klein. :)

Hillhater,
My trike will have 600 watts of exposed solar embedded in super sap clr in the roof and upper door skins so battery capacity isn't a big deal to me. Even considering that, at 2.6ah for $120, a very stable, light, and easily swappable 40v 10.4ah pack that has built in level monitors, protection at the cell level, and oem quality control can be built for less than $500. Counting the one that comes with the saw, for $700 total, the price of a 3220 or decent 15-20lb hub motor, you get a fan cooled 6374 outrunner in a custom case that's optimized for cooling and is easy to bole a reduction drive to, a controller, throttle, charger, and 12ah/40v of high output safe battery. At best, my last bike for 21wh/mile, and at worst, cruising up hills at top speed, 40 mph, it got 44wh/mile. That would be a 10-20 mile range with the four 2.6 and single 1.4ah battery packs and paralleling them all would output plenty of amps for sustained climbs. The motors and controllers in these saws are way higher quality than an infineon 12 fet and hk 6374. Reviews and my experience show that they can run hard all day if you have enough batteries.

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Re: Best RC motor for lightweight utility bike build

Post by Willjones017 » Jan 24 2015 10:15am

I would love to see the chain saw set up built that would be incredible!
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Re: Best RC motor for lightweight utility bike build

Post by mwkeefer » Mar 23 2015 9:20pm

Not sure if your looking for an Astro 3210 or 3220 but I have both and a Black Recumpence MS-eDrive complete setup. I even have an HV 120 ICE for the setup - The reduction of the v4 is 4:1 but the slipper clutch makes all the different.

Geared properly (say 37mph theoretical top speed) you should acheive an easy 35 sustained.

PM me if your interested in a single bulk package deal, I may have mounts but if not they can be ordered from Recumpence for your specific frame tube diameter... Custom mounts are easily made at your local machine shop.

I also have a Davinci Dual Stage Reduction with Motor Cradle and Aluminum Siipper Clutch - 3220 recommended minimum HV140 ICE or better and some darn tough cranks to handle the input :)

-Mike
Regards,
Mike

{My Rides]
2010 Dahon Jack - GNG v1 - LYEN 6FET - 20/40A - 18S2P10AH - Nom:66.6v,1332w
2004 Hard Rock Pro Disc - Recumpence ms eDrive v4 - Astro 3220 4T - 12S2P16AH - HV110 - Left Side Drive - Gearing: 38mph
Nominal Peak Power @ 60 seconds: 5328 watts - Maximum Power: 49.8v, 120A, 5872w
2010 Downtube 8FH - Stock GNG v1 Stock Controller - EB809XC - 12-16S
2012 Downtube Nova 7spd - Stock GNG v2 - 12S2P10AH - EB809 - 12S-16S - 20A/30A,Nom VCC: 44.4, 888w

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Re: Best RC motor for lightweight utility bike build

Post by spencer » Mar 31 2015 2:54pm

I'm thinking about making a motor mount with 4:1 reduction on my shapeoko 2 (don't have access to a student machine shop any more and this has been fun for wood working http://shop.shapeoko.com).

I see that people like the torque limiters - is there a good source for them? Mcmaster and Berg don't really have much of a selection.

I'm also wondering if I can start with a simple motor mount (no slots to mount the motor, just screw holes) by using a fixed position for the jack shaft and motor mount but adding a belt tensioner. Matt - we haven't met before but I read your project pages and am very impressed / inspired - what do you think about using belt tensioners in general and specifically with an Astro 3220?

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Re: Best RC motor for lightweight utility bike build

Post by ErnestoA » Apr 28 2015 10:39pm

Since recumpence is probably busy building amazing creations and hasn't chimed in yet, I figured I'd pitch in.

The dodge torque tamer slipper clutches are available from grainger at pretty good prices but they're heavy. Nothing a drill press can't take care of. If I remember right, the #25 size is the best one for putting on the driven pulley of the primary reduction. Baldor makes neat ones too but they ll do the same thing. I'd just buy the clutch pads and belleville washers and machine my own hub out of aluminum if I was going to do it again.

Toothed belts like a specific static tension. If you use a tensioner, get it tensioned and lock it off with a bolt. If your belt length needs to grow, you can use a sprung tensioner but belt life might not be as good. An 8m pitch belt is designed to have somewhere around ten lbs of static tension but ten lbs of tension on a spring might let the belt skip, which is no good. A tensioner that's sprung to allow for belt growth might have to pull at 50 lbs of force to prevent skipping, which is way outside of the recommended tension. If a tensioner is used, it's best to put it on the slack side of the belt, in a position that allows just enough belt wrap on the driver to handle the torque you need to transmit. Too much belt wrap wears belts quickly.

This is a great resource for belt drive design:
http://endless-sphere.com/forums/viewto ... 19#p557340

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Re: Best RC motor for lightweight utility bike build

Post by recumpence » Apr 29 2015 7:34am

ErnestoA wrote:Since recumpence is probably busy building amazing creations and hasn't chimed in yet, I figured I'd pitch in.

The dodge torque tamer slipper clutches are available from grainger at pretty good prices but they're heavy. Nothing a drill press can't take care of. If I remember right, the #25 size is the best one for putting on the driven pulley of the primary reduction. Baldor makes neat ones too but they ll do the same thing. I'd just buy the clutch pads and belleville washers and machine my own hub out of aluminum if I was going to do it again.

Toothed belts like a specific static tension. If you use a tensioner, get it tensioned and lock it off with a bolt. If your belt length needs to grow, you can use a sprung tensioner but belt life might not be as good. An 8m pitch belt is designed to have somewhere around ten lbs of static tension but ten lbs of tension on a spring might let the belt skip, which is no good. A tensioner that's sprung to allow for belt growth might have to pull at 50 lbs of force to prevent skipping, which is way outside of the recommended tension. If a tensioner is used, it's best to put it on the slack side of the belt, in a position that allows just enough belt wrap on the driver to handle the torque you need to transmit. Too much belt wrap wears belts quickly.

This is a great resource for belt drive design:
http://endless-sphere.com/forums/viewto ... 19#p557340
Belt drives are a bit tricky in that there are a HUGE number of factors at play when building one. There are engineering guidelines for sure. But, there are exceptions to many of the "Rules" regarding timing belts. It is actually a bit of a black art so to speak. For instance, I have found 8mm pitch to be very inefficient at high RPM. So, I have stayed with 5mm pitch and increased the width. This is far more efficient at the 8,000+ rpm I run and still holds enough power.

Building a reduction system is easy. Building one that handles high RPM, high torque, and is efficient using timing belts is tough. It is all about compromise and maximizing every parameter. I have built drives that seemed to work fine, but were hugely inefficient. I have built efficient drives that could not handle much torque. It took a lot of prototyping to achieve both in the same package. That drove the cost up, though. There are definitely cheaper ways to go, but you will ultimately sacrifice something. If range is not a big issue, don't worry about the efficiency. Build a reliable system and be done with it. If efficiency is a high priority, you will spend a lot of time getting it right on a cargo bike. It is definitely possible.

Another good option for torque limiters is Dalton manufacturing in Minneapolis.

Matt
1% of the world's population can think "Outside the box". The rest are firmly stuck within the box. Where are you?

ErnestoA   100 W

100 W
Posts: 162
Joined: Sep 23 2014 5:00am

Re: Best RC motor for lightweight utility bike build

Post by ErnestoA » Apr 29 2015 9:54am

It's definitely a balance of engineering and juju! You sure hit the sweet spot with the 5m pitch x 25mm wide primary reduction for the rpm of the Astros. After many hours of math, I came to the same conclusion. lol I referenced 8m pitch because I'm using it for everything after the primary reduction in my next project and the numbers were fresh in my head. It seems like in each drive setup, little compromises will have to be made in regards to factory recommendations but when it all works out in the end, it's pretty much magic. :lol:

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