E-Trials bike input needed

[gwhy!]

As some of you may have aready seen the thread http://endless-sphere.com/forums/viewtopic.php?f=28&t=8243 that started off about CVT and progressed to the reason why I was asking .

I would like to try and build a e-trials bike that will be competitive/fun to ride. I currently have a 350w my???? 24v and 36v 1kw my???? motors with cheap batterys and controllers, these will be used to find the best gearing for the purpose but not used in the final build I have been pointed towards using a RC setup because of weight, size and efficiency.

The prototype bike will be built on a 14" jumpbike hardtail frame using 20" wheels but with front suspension. For peeps that do not know what trial bikes are, they are the funny looking bikes without a seat and are geared very very low that enables the bike to be launched up stuff using the drive train.

or the gas type

It has already been suggested the there should be no current limiting to the motor for a short burst of time.

Please bare in mind that I am new to all this and I am on a very steep learning curve about current motor and battery technology . I used to race electric model cars about 20+ years ago and things have changed a lot since then :? . So please be gentle with me if I ask something that should be obvious..

So thats it I have the bike, a few big heavy motors a few big heavy batterys I think the main problem is to produce a drive train that is small enough and can handle the torque needed, changable gears would be good but no essential.

open to suggetions please

 

[safe]

More on that pushbutton idea...

SPST 0-100Vdc 40A DC Solid State Relay - $19.90

http://www.futurlec.com/RelSS.shtml

People are going to crack up if they read this:

"Oh no! Safe is talking about Solid State Relays again."

...but in this case it might actually make some sense. Since you don't want to actually have your thumb next to the actual motor current (too dangerous) you could use a Solid State Relay to do the actual work of switching and then use some low voltage button to trigger it. This could allow you to come up with whatever button device you seem to like. (some creative ideas could be possible)

For $20 that's less than most controllers... so for a first time testing idea it's not going to break the budget if it doesn't turn out right.

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Typical ebike throttles work from 0-4 volts which would be enough to trigger the switch. (just barely) So full throttle might be "on" and anything less would be "off". Not sure if you want something as imprecise as these ebike throttles though... they aren't really all that good.

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A good place to browse for cheap parts:

http://tncscooters.com/partsdb.php?type=ES

 

[gwhy!]

It totally makes sence for this application you dont want to be running battery/motor wires upto the bars, would need to keep all those high current carrying wires as short as possible. do you think one 40A relay will be enough if i use a high current motor ?, may need a few of them :lol: I will see if I can pick up a cheap contactor from somewhere for testing purposes less likly to blow it up .. Cheers safe it shouldnt be to difficult to mod one of the controllers i have to produce a output to drive a relay at full throttle..

 

[safe]

40 amp, 100 volts is 4000 watts of power. (power is what matters)

Hmmmm... you know one problem is that you need to be careful on the choice of battery too. Many batteries do not like to be pulled at high "C" rates and this is going to be pretty high for short bursts.

If you know what motor you will be using we can use my simulation program to get some idea what the powerband would look like.

Is it the MY1016 or MY1016Z3 (with geardown)?

 

[gwhy!]

its the my1016 thats the 350w one I also have the 1 kw one is it a my1018 ?

 

[safe]

Massive Torque


Let me explain what this is. This is the torque for the MY1016Z3 with the 10 to 1 geardown built in. I have this motor myself... it's not a bad place to start.

Look at the flat blue line on the bottom and that's if you do something rather unsual like I am doing and using an Armature Current Limiting controller. The green is a standard controller and the red is no controller at all. (pushbutton)

So if you do the math the actual torque that will come off the sprocket is ten times as much, so about:

50 Nm.

For comparison.... 100 Nm at the rear hub is generally the point where most everything will break. So you would be halfway to hub failure with this. (probably normal for trials that always pull big torque)

On another chart (I didn't post) the maximum current looks to be 100 amps for a 24 volt system. If you increase the volts you also increase all these numbers. (so everything will get more stressed at the higher voltage)

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Too late... I just posted for the other one.... the results would be similiar for the MY1016 but you will have to design your own geardown rather than use the built in one.

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The red line really shows why an unlimited system makes the most sense for a Trials bike because without it you are giving away a lot of low end torque that you would like to have.

Lot's of heat though.... something that needs to be watched...

One second of this much power would be the equivalent of the hardest crank your body could produce I suspect. (would need to do some more calculations to be sure)

 

[gwhy!]

Uhmmm When I built my first e-bike just before christmas I just bought bits (350w)and bolted them together it was geared to do a max of 18mph though a 6 speed derailer on 20" wheels, when i test rode it up and down the steet i thought it was ok but instantly thought I must get a bigger motor but it was when my daughter had a go on it and she popped a tiny wheelie in first gear then I thought intresting ( she is nearly 3 stone lighter than me :lol: ) and thats what has got me into all this, so the weak link in my old mk1 v1 bike was the speed controller ( maybe the batterys aswell ) That chart looks very intresting indeed. I really need to get mk1 v2 up and running to take some readings and also see what my current batterys can chuck out. :wink:

 

[fechter]

More on that pushbutton idea...

SPST 0-100Vdc 40A DC Solid State Relay - $19.90

http://www.futurlec.com/RelSS.shtml

People are going to crack up if they read this:

"Oh no! Safe is talking about Solid State Relays again."

I'm not sure that will handle the current.

I used to live in Moab back in the days when you could ride a motorcycle anywhere. I did a lot of trials-like riding, going over boulders and steps in the rocks etc. It's real Road Runner vs. Cyote land around there.

You need a motor with a lot of grunt and some big amps to make it jump. Most trials riding is at very low speed, so motor cooling could be an issue.

Weight is pretty critical also. Lead acid batteries are going to suck, but might be OK for very limited range testing.

I have seen a few electric trials bikes, most based on the original Etek motor. Those would be great with the right gearing. Problem is they are no longer produced. The new Etek-R is larger and heavier and could be challenging to stuff into a trials frame. These are way too big for a bicycle.

Most hub motors would be geared too high for rock crawling.

More on the bicycle end of the spectrum you might consider some kind of bottom bracket drive so you can use the bike's gears. There is not much in the market available here. The Cyclone 1000w unit might be close.
Home made RC motor drives are another option, but DIY intensive.

 

[MitchJi]

http://endless-sphere.com/forums/viewtopic.php?f=28&t=8063

 

[B0B]

Hi there,

I'm a very keen trials rider myself!




I'm not sure if i got the jist of what you wanted from the push button activation, but a variable throttle will be much more usable! As for power and the such, torque is the important factor when chossing drivetrain and motors. if you're using a push bike frame to try this with, a hub motor wouldn't do, because the gearing inside will fail in a very short time if given a lot of knock starts as proven at our EV meeting we held and broke two motors because of it. also the wieght would be far too much to be able to lift the bike when needed. RC mtor would be the way to go. Also with that, you can get the gearing low enoguh to give you the torque you'll need. bearing in mind you'll never need to go above 10 or so MPH!!
As for mounting the drive train, you could buy a disc brake rear MTB hub and mount the drive sproket on the disc mount so there is no interfirence from the origanal drive. Have the battery pack in a back pack so the bike has minimal added weight, and use good quality lithium cells so you can get max current out of the pack.

anyway, if I'm ont the right path for you, I'm involved in a project to use an RC motor for a Kona Stinky for off road use and can keep you updated on how we get on with it.

 

[safe]

...the weight would be far too much to be able to lift the bike when needed. RC mtor would be the way to go. Also with that, you can get the gearing low enoguh to give you the torque you'll need. bearing in mind you'll never need to go above 10 or so MPH!!
As for mounting the drive train, you could buy a disc brake rear MTB hub and mount the drive sproket on the disc mount so there is no interfirence from the origanal drive. Have the battery pack in a back pack so the bike has minimal added weight, and use good quality lithium cells so you can get max current out of the pack.

Those are all expensive items... the RC motor and good quality lithium cells are not cheap.

As for the left side mounting of the motor to rear wheel, that does sound like the best way to go. For the torque that would be needed you need a linkage that isn't going to break.

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Driveline Snatch?

When the motor suddenly revs up it's going to pull up all the slack in the chain and when that happens the shock will tend to break something. The less driveline snatch you can have the better.

Ideally you would use something with a geared gear reduction rather than a chain driven one.

Recumpence on his RC motor system uses belts and he has had troubles in the past with them breaking. (though things are better now) At the very least I would suggest going to one of the motors like the MY1060Z3 that has a built in 10:1 geardown so that you don't have as many chain problems. (I've used multiple chains and it's not the best way to go)

The MY1060Z3 only costs $55.

I would think a MY1060Z3 that was directly attached to the rear wheel on the left hand side would deliver everything needed.

The pushbutton idea needs to be combined with a temperature gauge in the motor so after a certain number of activations the pushbutton is disabled until the motor cools off. This circuit would involve a single comparator and that's about it. (figure out the temperature sensor voltage at overheating and compare that to a baseline voltage)

The MY1018Z motors are another good choice in the same price range:

...you are creating an enormous amount of extra work by starting with a motor without a geardown, so this is one area where the $50 - $60 is worth it. Cheap is good, but sometimes being too cheap is counter productive.

 

[safe]

I'm not sure that will handle the current.

It's worth trying a cheap and lightweight motor and seeing if it can work first before investing in the more expensive stuff.

Ultimately the best thing would be an RC motor... but the technical issues on that would be hard to handle. The motors with built in geardowns can basically be bolted on directly and tested.

I've triggered my own MY1060Z3 using direct battery contact and it didn't fail or anything. There was no load on it, so it wasn't a good test. For Trials it's going to produce a lot of torque in a short burst. The chances are that something will break... but you never know if it's the motor, the gears, or the chain... or even the hub... until you try it.

Trials riding wants bursts of power... the opposite of what I'm doing where I want peak power delivered smoothly... so I'm fascinated at how people are testing both ends of the spectrum at the same time.

A heat protection circuit should be mandatory on this.

Also... it might be a good idea to upgrade the wires that go into the motor to a higher gauge. (this is something I did on my motor)

 

[Ypedal]

more like a waste of 50 $.. that puny thing would fry in no time.. for trials grunt you need big amps and light weight...

 

[deecanio]

suggest you keep an eyes on Matts trials bike build and see if it's for you?
RC gear is expensive.But so is testing with cheap gear before upgrading to rc gear.

Cheers,

D

 

[safe]

more like a waste of 50 $.. that puny thing would fry in no time...

But "time" is what we are thinking about.

How much "time" can a burst of energy go through the system before the heat becomes a problem?

A timed pulse of a known quantity would be ideal... that way you hit it with as much energy as possible before you need to let off.

The RC motor solution is going to end up being $500 or more before you are through, so a 1/10 price test is worth seeing what it would be like.

For "pioneer testing" you figure that a 1/10 price is worth sacrificing for the sake of the longer term objective.

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There are controllers out there that offer unlimited current... so it's not like it's impossible to do.

Don't let these big $$$ folks scare you into giving up... keep up the spirit and test with cheap stuff first.

Discouragement is the quickest way to lose...

(I've seen this time and time again)

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gwhy! is on a low budget and all this talk of expensive stuff does not help...

 

[gwhy!]

I wont be giving up . I already have the motors ( 350w and 1kw ) the money is already gone so I will be playing with these to get a feel for it :wink: I think I will defo go with a RC setup but not going down that route just yet until im sure its doable and give me the performance that im hopeing for. I will be watching Matts build with intrest . I havent long taken up cycle trials and Im not very good but really enjoy it, But I have been riding mototrials for 6-8 years and know all the theory even if i cant "always" put it into practice . So my expectations may be set a little high (mototrials).. . I do intend selling one of my mototrials bikes to finance this project ( to get a RC motor setup with some very good batterys ). The idea of unlimited current for a short burst of time when moving from a standing start is a very good one but will still need a throttle.

 

[TylerDurden]

For fifty bux you can get a starter relay that will handle 200A. Actually, you might be able to get two or three.

In the EV/forklift world, power relays are called "contactors".

(If safe has proven anything, it's that undersizing a system makes money turn into smoke.)

 

[fechter]

I'm not sure what kind of top speed you need for trials. Seems like it would be pretty low, which would allow you to gear the motor very low and get tons of torque. It doesn't take a really big motor to equal a human.

It should be possible to make a throttle with a very short travel. If you used a pot box, you could make the travel adjustable. There are electronic ways to shorten the travel also.

 

[gwhy!]

Next time i go out on my cycle trials i will attach a speedo to confirm actual speeds used may even take the mototrials out aswell with the speedo attached, im guessing between 8-12 mph max on the cycle and 20-25max on the moto.

 

[j3tch1u]

for the amount of torque and power/weight ratio you are looking for i'd suggest pairing a 200kv outrunner with an electromagnetic particle clutch (not cheap). these clutches handle continuous slip and do not wear out. using a reversed pot thumb throttle to engage/disengage the clutch, you can have great torque control. feed the 12v or 24v clutch with a dc-dc convertor off your batts. rev the motor, pop the clutch and over the rock you go!

 

[safe]

Maybe a good idea... that way the motor can spin up to higher rpms and then you can transfer the stress to the clutch and away from the motor. Since the motor uses next to no energy when running at it's no load speed you could have it spinning most of the time and then dump the clutch as needed. Maybe even add a flywheel to the motor so that it has even more energy built up. You could use a very small motor and yet get tons of torque in a surge doing that.

Hmmmmmmmmmmmmm...

In real Trials riding they use a clutch to trigger the power anyway right?

So this might actually be more "normal" for Trials riders used to gasoline power.

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Ironically such a bike would be illegal in my state of Missouri because that's one thing (a clutch) they thought was too complex for children using mopeds.

It still seems easier to just use the motor torque: (there's plenty of it)

(it seems like I posted something a couple back that got deleted or something... hmmmmmm...)

 

[safe]

How About Both?

What if the throttle simply turned the motor on or off and the clutch was used to deliver measured amounts of power?

That way you still have maximum and unrestricted torque (no current limits) when you really need it, but you can dump the clutch when desired or let it out slowly too.

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I suppose the ideal thing would be to buy a motorcycle controller (100 amps or more) that can handle higher amps and then you could have all the best options. The throttle would be smooth and unlimited and the clutch would allow you to apply the power more precisely.

The typical 30 - 40 amp ebike brushed motor controller is just too restrictive...

(but I suppose the RC motors are actually unrestricted by default aren't they? :wink: )

Hmmmmmm... again the RC motor looks to be the winner. (maybe)

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Ultimately you have to ask whether you want to explore the unique advantages of the electric motor powerband (very high low end torque) and seek to "spin up" really fast. OR you need to go the other way and have some flywheel and build the energy up when the clutch is pulled in. It makes no sense to use such a low intertia device as an RC motor with a clutch because dumping the clutch doesn't deliver much. The RC motors give power by "doing it" and not carrying it by inertia.

See what I'm thinking.... there's a contradiction going on.... :?

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One more thing... using a clutch might mean you don't need a freewheel. That's one less thing to worry about in the design of the transmission system. So that goes on the "plus" side for clutches.

I kind of like the clutch idea.

 

[j3tch1u]

hi safe, great bike btw (just saw your build threads). you did a great job. like yours, mine is also somewhat of a motorcycle hybrid design. so i'm looking for more power. i'm experimenting with electromagnetic clutches on my new powertrain. mine's not for trials so i'll probably go with a dry clutch (thin profile), hxt 130 and some sort of multi-speed fixed gear hub. what i'm trying to accomplish with all this is selective regen braking for max efficiency.

accelerating: clutch may slip or engage in forward direction
coasting: no throttle, no brake, clutch is disengaged
braking: brake lever simultaneously operates a pot that engages clutch for regen
normal pedalling: clutch is disengaged
fred flintstone: pedalling with clutch to charge batts

hopefully the regen will make up for the power draw from the clutch (around 10W avg). won't know unless i try.

 

[Lock]

I have seen a few electric trials bikes, most based on the original Etek motor. Those would be great with the right gearing. Problem is they are no longer produced.

But still available if you are quick:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=300287263324
tks
loCk

 

[gwhy!]

right,,,
I have got all my old drivetrain together and loosley fitted to my old 14" jump frame fitted with 20" wheels ( this is what i used just before christmas as a chuck together e-bike but was mounted on a 24" wheel mountain bike ) I have some better ideas for a much more robust, quieter drivetrain but this will do for testing purposes or even just to see if it brakes :lol: . There are a few things that need to be sorted out with alignments but shouldn't be to much of a problem.