weight comparison

[Kurt]

I had my rc drive removed from my trike yesterday just to paint a section of my trike frame. Anyhow I wanted to weigh all the components.


V4 reduction drive with primary belt ,2'' tube mounts, 1920g
Rear aluminium toothed pully , 6 mounting bolts and gates toothed drive belt 465g
Turnigy 80 100 motor with 20 tooth sprocket 1950g
Heavy duty MTB rear wheel hub with disk bake mount 500g

Total weight 4.835KG

I didn't want to weigh battery's ,controller,CA and so on as I wanted to use it as a direct comparison to a hub motor. I included the weight of the rear wheel hub because when running a hub motor the rear wheel hub is included into the hub motor.

My particular set-up is accentually a fixed gear ratio electric drive with free wheeling ability. So I guess you could compare it to geared hub motors as they are fixed gear reduction with free wheeling.

A 500w 48v Bafang geared hub motor is 4.9KG so exactly the same weight and ticks the box for fixed gear reduction and free wheeling.

I don't know how the 500w Bafang would go with 36v 40A controller for 1400w peak.Although it should be fine as the stock controller is 25A for 48v so 1200w peak. I am tempted to buy one just to play with as they are only $180 laced to a 20" wheel with a 25A controller as I think they are sensor less motors ?.I could mod the controller to let it draw 40a for a fare comparison or limit my RC drive controller to 25a with the CA. Or even fit hall sensors to the Bafang motor and use the same controller. Would be interesting to do back to back comparisons with the RC drive .

I am not sure what the BMC motors weigh ?

Then there is the option of mounting a rear Bafang and my RC drive at the same time as the Bafang has a 6 bolt ISO disk brake mount The two drive units would weigh about the same as one 9c motor :lol: and about 4kg less than one x5 hub.

Anyhow I like collecting data and doing apples for apples comparisons and just thought this was interesting. A low powerd RC drive system like I am running Is way more efficient than a direct drive Hub and much more pleasurable to ride due to the free wheeling ability and low weight. I am on the fence about using a RC drive for day to day commuting or long distance riding. Its a bit like when I had a very modified old school honda civic running quad super bike carbs and a 10,000rpm rev limit. Very addictive to drive short distances, race events, hill climbs , drag race it but it was more of a toy than transport at 700kg sound deadening was a after thought .

I'm thinking the RC drive is the same and makes a better racer toy than leisure transport. By this I am thinking if you are going to live with the down sides of a rc drive.The two big ones in my book are Noise and complexity then you are better off taking advantage of the + sides . Potential BIG power at high rpm and light weight and treat it like a weekend race car.

Kurt.

 

[Miles]

Thanks for the data, Kurt.

My target weight is 1.5 kg - for motor, 2-stage reduction drive and 2 speed gearbox. That doesn't include the rear hub, though.......

 

[Kurt]

1.5kg sounds great but would be a challenge. You must be using a very small or light weight motor? The 80-100 I have is already 1.95kg.Even the little turnigy Aerodrive motors are between 700- 800g. I guess you are using synthetic pulleys and toothed belts?

Kurt

 

[Miles]

I've allowed myself 500g for the motor. Pulleys are Aluminium alloy. Gears and shafts are steel. Mounts are CFC.

 

[deVries]

I'm thinking the RC drive is the same and makes a better racer toy than leisure transport. By this I am thinking if you are going to live with the down sides of a rc drive.The two big ones in my book are Noise and complexity then you are better off taking advantage of the + sides . Potential BIG power at high rpm and light weight and treat it like a weekend race car.

RC weight is MUCH HIGHER than I thought... your set-up Kurt is 10-lbs 10oz.

I'll weigh my MAC motor & post here in a few weeks if someone else doesn't beat me to it.

What would be a very interesting research project would be to learn which RC set-up is much lighter weight vs other RC setups too.

Really, great post idea Kurt Can't believe this hasn't be explored before in great detail...

Thanks

I've allowed myself 500g for the motor. Pulleys are Aluminium alloy. Gears are steel.

Is this a production for sale motor you're developing

 

[Miles]

Is this a production for sale motor you're developing

Nope.

http://www.xeramotors.com/index.php?page=shop.product_details&product_id=10&category_id=1&flypage=flypage-ask.tpl&option=com_virtuemart&Itemid=1

 

[full-throttle]

Thanks for the figures.

500W Bafang BPM is supposed to be 3.9kg not 4.9kg. Don't forget they are intrinsically sealed BenMoore (Melbourne) has them with Hall sensors installed. It should last well with 1400W - mine has done over 20,000km so far.

 

[Kurt]

xeramotors look nice. A reasonable mid range price and the option for a 8mm shaft is nice. My technical know how in breaking down the listed motor specifications isn't the best. I could see the one you linked to was 300kv.I would say a two stage reduction would be needed at 300kv even with a 20" wheel. What wattage/amp rating would that motor have?

Thanks for the figures.

500W Bafang BPM is supposed to be 3.9kg not 4.9kg. Don't forget they are intrinsically sealed BenMoore (Melbourne) has them with Hall sensors installed. It should last well with 1400W - mine has done over 20,000km so far.

Only 3.9kg for the 500w that even better. The data on the web page I went to were out of whack.I can also see the 250w rear wheel model is only 2.8kg. I guess integrating everything in the one unit is always going to be a easy way to save weight . I bit like a laptop compared to a desktop.

Mind you you have to be fare as the RC drive and motor I have is capable of 10kw in short bursts and is factory rated at 6kw.

Its interesting last night I had my old 5304 bare motor mounted up in my lathe and spun it up under power. The castings have so much run out in them I am amazed I was ever able to true the wheel on it. Quiet and has some torque but its just built like rubbish. The axle is made of cheese and the casting have more bubbles than a sink full of detergent . At 12kg it doesn't belong on a bike frame and don't even mention the cogging resistance. I think I will use it to generate stationary power wind, hydro something like that in the future.

A 500w bafang that has halls installed from a Au suppler would be great have to look into that. I just want one to play with .

Kurt

 

[Miles]

I could see the one you linked to was 300kv.I would say a two stage reduction would be needed at 300kv even with a 20" wheel. What wattage/amp rating would that motor have?

Yes. Reduction ratios are 20:1 and 40:1 (20" wheel). I'll be using the motor to put out up to 1200 watts cont.

 

[deVries]

Yes. Reduction ratios are 20:1 and 40:1 (20" wheel). I'll be using the motor to put out up to 1200 watts cont.

Will you do a build thread, please? What other eBike R&D projects are you working on

 

[Miles]

Will you do a build thread, please? What other eBike R&D projects are you working on

In due course

Recently, I've concentrated all my attention on 2-speed gearbox designs.

 

[Kurt]

Thanks for the figures.

500W Bafang BPM is supposed to be 3.9kg not 4.9kg. Don't forget they are intrinsically sealed BenMoore (Melbourne) has them with Hall sensors installed. It should last well with 1400W - mine has done over 20,000km so far.

So the 500w bafang BPM is available with halls installed? Also I'm not up on all the different specs like code 9 or code 11 motor. I assume its different winds for wheel sizes? What's the fastest one as I want to lace one in a 20" wheel and I would prefer to get one that's not going to run at 5km because its designed for a 700c wheel LOL.I can see one rater at 36v - 48v and 340rpm not sure if that's at 36v or 48v as 340rpm in a 20" is only 30kmh. Where is the best place to get them from given I am in Au ?

Sorry about all the questions. I did some searching, but it did my head in. Everyone is calling them different names and so on. It was hard to get a clear idea of what was what.

Kurt

 

[recumpence]

As miles has mentioned, RC sytems can be made MUCH lighter. The issue of weight in Kurt's example is that his motor and the drive system are capable of 8-9kw of power. That much power in that light a package is where these systems shine.

He is correct about the systems being more focussed on performance than reliability. That being said, I have a couple systems with over 1,000 miles without any problems at all. But, I want to see 5,000 miles one on system before I am ready to declare that these are truely great long distance systems.

The sound of an RC system is a personal preference thing. Some people really like it, others want total silence. It is hard to beat hubbies in the silence department.

Matt

 

[wojtek]

I think BMC V2/V3 weight 4kg.

the weight of your kit to power ration is unbeatable!

 

[Kurt]

Its no a dig at all regarding the rc drive be any means. I am just trying to work out what to expect and what application it fits best for me personally. In all honesty I see myself fitting the drive to a modified off road mtb with 24" wheels. perhaps to gain some speed without the need for extra RPM and to have the potential to extract some serious power from the RC motor. In that configuration I would be wearing a full faced helmet and my head wouldn't be 8' away from the motor like in a trike so sound wouldn't be as big of a concern.

I'm particularly concerned with the noise. I am not aggravated by it while riding the bike. its more of a heath concern. as I already have a mild case of tinnitus "constant ringing in ears" From working in a engineering workshop for many years. I don't want to risk that getting worse to the point were it effects my daily life.I tend to just use a set of monitor ear plug headphones when I ride the rc drive that have a 50db reduction.Though I am a little more reluctant to take my daughter on it to much and risk her hearing as there are peaks of over 100db at wot with two different DB meters and at the end of the frequency range that dose the most damage. Other brand of motors could be better but I would have to see the raw data before I believe that. No big deal just have to treat that noise with respect like you would a power tool or machine and use protection.

Reliability I feel the drive its self is over engineered considering its weight especially for what I am doing with it 1.5 kw and the drive its self is smooth and silent.I do have some small concerns with longevity of the aluminium drive pulleys when the belts are open to the elements . I noticed my m5 80 tooth pulley was marred from what I guess is fine sand or grit from my suburban bike paths and the odd grass park crossing. I have about 200km on it its not bad but given enough miles A sealed belt cover would go a long way and make it last for ever. The m8 belt and pulley had no noticeable marks and that's good as its harder to cover.

Anyhow the rc drive has its place. My trike will most likely get a geared hub just for practicality and the rc drive will become my toy or weekend ride

Kurt

 

[wojtek]

re the noise, how i see it:

1. in town / city you want to be HEARD!!!! So from this perspective, im happy with my RC turnigy drive - i dont care that it is loud. People see me, cars can probably hear me...
2. off-road - i love to be quiet! just enjoy the sounds of the nature. So now im building off road trike with crystalyte 5404 on Steintrike Mungo sport fully suspended. Probably 88v Turnigy 30c lipos and greatest Lyen controller.

However there is a huge problem - the weight of the rear wheel for off-road riding. It will be around 12.5 incl spokes and rim.

Im also getting velokraft off-road fully suspended prototype with Matts 3220 dual chain drive at some stage this year. Light rear wheel but noisy.

 

[Kurt]

I think BMC V2/V3 weight 4kg.weight of your kit to power ration is unbeatable!

Thanks for the Info on the BMC.

Yes power to weight the little rc out runners are surprising. I get the feeling I could comfortable double the power Of my setup and still be 100% reliable in any situation.Most of the geared hubs look to be in the 2kg to 4KG with power rating from 200w to about 2000w max range and rc drives from 1.5kg to around 4kg From around 1000w to 10kw.

I would be interested in some noise data on other peoples RC drives motor combinations. DB rating from 1m distance at full throttle. Anyone with a Iphone or Ipod can download a free application that gives you DB readings . Not sure about android phones. I have tested the application against a dedicated db meter and its surprisingly accurate.

Kurt

 

[deVries]

Most of the geared hubs look to be in the 2kg to 4KG with power rating from 200w to about 2000w max range and rc drives from 1.5kg to around 4kg From around 1000w to 10kw.

What about not mounting the BMC/MAC inside the wheel? Can't the power levels go way up on these motors too with one big sprocket gear reduction, since these already have the built-in gearing reduction or call it "first stage" inside?

Any commentary from our resident gearhead experts

 

[Kurt]

Today my sensored :wink: bafang 500w code 9 geared hub arrived.

I will be lacing it into the identical Sunrhyno lite 20" rim as my rc drive uses. I will be able to do back to back testing on 36,48 and 60 v lipo at 40amps using the same controller and battery's. I plan to ride identical mixed terrain circuit of around 35km and report back in detail of the results.

I weighed both the BMC motor and the complete rc drive. Remember the with the rc drive you have to add in the weight of your rear wheel hub to give a apples for apples comparison.The hub becomes part of the motor with the bafang. The wheel hub I used for my rc drive 20" wheel is one designed for DH MTB and is around 500g.You could get lighter but if you want the strength for putting a few KW of power through it 500g is about average weight..

Weighed both on accurate digital scale

BPM motor is 3999g so lets say 4.00 kg

RC drive is 4265g + 500 for hub 4.75 kg

They will be fed identical power from identical battery all that will be changed is the motor and drive system.

I understand they are both designed to do different things. the comparison and test results are not intended to knock one drive style over the other. I just think it will be a very interesting and reasonably fare comparison. Given there similar weight and are both free wheeling and the fact i can test them under identical conditions.

Another interesting thing is it is actually possible to mount the final large aluminium toothed pully from the RC belt drive onto the disk brake mount of the bafang motor.and run both motors at the same time. Total weight for the dual drive would be 8.26kg. Not sure what the advantage would be but it would be cool though. Hub motor for quiet stealthy relaxing riding. Rc drive when you want to spin the back wheel and race some one. Or both at the same time with dual 12 fet controllers when you just want to be stupid LOL.

Back soon with the detailed data.

Kurt

 

[Miles]

Today my censored bafang 500w code 9 geared hub arrived.

X-rated?

 

[adrian_sm]

Here is another couple of data points of system weights from some friction drives.

<2kw Friction Drive - 63mm motor

<1kw model Friction drive - 50mm motor

Summary:
4.8kg = Matt Schumaker RC 4.3kg + 0.5kg (strong hub) > 2kW
4.0kg = BMC V2/V3 or BPM <2kW
1.7kg = 63mm Friction Drive 1.3kg + 0.4kg (normal rear hub) <2kW
1.2kg = 50mm Friction drive 0.8kg + 0.4kg (normal rear hub) <1kW

Oh and if you wanted a 80mm motor, for more power.

 

[Kurt]

Thanks for that info. The friction drive's win hands down when it comes to low weight. I will have to mention the rc reduction drive is capable of 10kw without breaking.But for this test I will cap it a 2400w when I do the 15s lipo test at 40A.

I just got the bafang wired up to the 40a 12 fet controller. I got lucky and got the wire combo 1st go :lol: Even though I got the code9 the fast wind. It sure is a different experience to the rc drive with things spinning at 8,000rpm . Even at 60v it doesn't look like its spinning fast without a wheel attached.Its got some very nice torque. Should make a great hill climber in a 20" wheel. I think it will do about 45kmh at 15s. I was a bit disappointed that the hub had some run-out you could visually see when you spun it up.The free wheeling action needs some running in but is getting looser.

Just need to get it laced into a rim and the testing can begin .

Kurt

 

[adrian_sm]

60V40A sounds like a lot for that little guy. Not sure how many have survived those power levels.

I know full-throttle has got a lot of k's on his, I seem to remember he had an opinion on what sort of power levels it could handle. (<1.5kW)
Might be worth asking him about it before you cook the motor, or turn your gears into mush.
http://www.endless-sphere.com/forums/viewtopic.php?f=6&t=15066&p=298418&hilit=code9#p316241

 

[Kurt]

Yes I will limit the amps through the CA to 25A for initial testing at 15s and decide befor runnign that kind of power through it. i wouldnt run that kind of power full time as there wouldn't be much point. 1500w is plenty in a geared hub.

I do feel that in a 20" wheel the motors have a much easyer life than in a 26" wheel though. Especially from 0- 50% of full speed under load. Like full throttle starts from a stop no peddling or even very steep hills.

Kurt

 

[recumpence]

Here is another couple of data points of system weights from some friction drives.

<2kw Friction Drive - 63mm motor

<1kw model Friction drive - 50mm motor

Summary:
4.8kg = Matt Schumaker RC 4.3kg + 0.5kg (strong hub) > 2kW
4.0kg = BMC V2/V3 or BPM <2kW
1.7kg = 63mm Friction Drive 1.3kg + 0.4kg (normal rear hub) <2kW
1.2kg = 50mm Friction drive 0.8kg + 0.4kg (normal rear hub) <1kW

Oh and if you wanted a 80mm motor, for more power.

That is not an apples to apples comparison. I pull 9kw through my RC sytems all the time without any problems what-so-ever. So, at 4.5 times the power of your friction drive, the power to weight ratio is way over on the other side. :wink: Also, the rest of the bike plus the rider puts the power to weight ratio through the roof.

I am all for ultra light systems. But, lets make sure we keep everything in perspective.

Matt