E-Ram

[Deleted member 4366]

These guys sent some of us details of their system in the hope hat we wold give it a plug on the forum. I think it has enough merit to give it a mention.

As far as I can make out, it uses a double wobble gear to reduce the motor speed o crank-speed. The wobble gears are walked round the ring gear by an eccentric boss, so the ring gear rotates in the opposite direction with large torque. This is how a recliner mechanism works in car seats.

The main point of the E-Ram system is that it's very light. It looks like we have a lot of good things to look forward to in the future as things develop further.

https://www.kickstarter.com/projects/159947242/the-e-mountainbike-revolution-bionicon-edison-evo

https://en.m.wikipedia.org/wiki/Cycloidal_drive

 

[shemozzle999]

These guys sent some of us details of their system in the hope hat we wold give it a plug on the forum. I think it has enough merit to give it a mention.

As far as I can make out, it uses a double wobble gear to reduce the motor speed o crank-speed. The wobble gears are walked round the ring gear by an eccentric boss, so the ring gear rotates in the opposite direction with large torque. This is how a recliner mechanism works in car seats.

The main point of the E-Ram system is that it's very light. It looks like we have a lot of good things to look forward to in the future as things develop further.

https://www.kickstarter.com/projects/159947242/the-e-mountainbike-revolution-bionicon-edison-evo

https://en.m.wikipedia.org/wiki/Cycloidal_drive

Unfortunately only OEM as it requires a BSA bottom bracket, but agree that the bike itself offers a new way forward:

http://evo.bionicon.com/en/revo-pre-sale/

 

[Deleted member 4366]

BSA bottom bracket is the standard that's on most of our bikes, so I would say that's fortunate, not unfortunate!

 

[EddiePJ]

A 2.609kg weight saving on the motor, over that of the current Bosch Performance line is good, but sod riding around with potentially 4kg of battery pack in a rucksack, along with the massive inconvenience of having a cable that could and will get caught up on something.

 

[Deleted member 4366]

There's nothing to sop you using a normal bottle battery. I'm sure that'll be an option when they go into production.

 

[trex]

Difference for difference's sake.
too expensive for what it is. I can't see the advantage of their two stage wobble gearbox against a well proven two stage reduction on the BBS01's gearbox.
They did put forward a good argument in support of their design goal though.

 

[Croxden]

I thought it would be great for the Birdy but at £1750 it's a bit dear.

 

[HillyBilly]

Its a question of risk?
Is the" Holy Grail "of power to weight ratio,worth the risk .
Possibly yes if you are a down hill mountain biker looking for the flow or an owner of a lightweight folder with a dodgy back and big hills to climb.
I think Bionicons goal has been to allow unassisted cycling to be as unaffected as possible yet give approximately an hour of climbing torque?
Quite an ask .As i would imagine high torque e bikes require a low power setting to feel like a equivalent standard bike on the level?
Am i a risk taking pioneer or is there an alternative?

 

[EddiePJ]

There's nothing to sop you using a normal bottle battery. I'm sure that'll be an option when they go into production.

For sure, but one aspect that they have honed in on is weight.
If their basis is 13kg for the bike, plus 2.609kg for the motor excluding ancillaries and frame mounted battery, then adding that little lot up over and above, you could perhaps end up matching the weight of some current e-mtb's, which would or could be a considerably cheaper cost option.

 

[Deleted member 4366]

Whether you have the battey in a bckpack or tied to the frame, it's the same weight!

 

[EddiePJ]

I realise that, but the point that I was making was that they had left this minor detail out, when referring to weight.
I don't know what a complete Oxygen kit weighs, but I bet that the figure won't be so far removed from this kit. Possibly 1- 1.5kg of difference? To my mind a product would need more than that to make it stand out.
I also can't see many wanting to flaff around swapping components to convert from an assisted bike to non assisted bike. The novelty would quickly wear off, and you would soon just buy a second bike.

Conveniently there is more that they aren't saying, than they are saying.

If this were Dragons Den, I'd be saying "I'm out"

 

[mike killay]

Having read about cycloidal drive on Wiki, two questions arise.
1 Wear, it's OK for car seats but will it wear out quickly if used continuously?
2 It cannot be driven backwards, not very handy on a bike.

 

[trex]

2 It cannot be driven backwards, not very handy on a bike.

I think they added a sprag clutch for this but the wobbly gearbox wobbles the bike.

 

[Deleted member 4366]

The clutch is so that you can pedal indpendently from the motor, so, if it's a sprag or roller clutch, it'll be in the wrong direction for pushing the bike backwards.

Some versions of the Xiongda cannot be pushed backwards in some circumstances. It's a very small inconvenience, and in some circumstances can even be an advantage. It might not be so good on a heavy trike.

 

[trex]

it will drive me nuts if I can't move the bike backwards.
if the key advantage of their wobbly gearbox is saving 1kg then it'll be a lot cheaper getting the same weight reduction by replacing the 2.7kgs average suspension fork with a good quality air fork.

 

[Deleted member 4366]

Or eating a few less pies.

 

[HillyBilly]

Or " poppy seed pastry".
A reply from Bionicon today; hopefully self explanatory to my questions.
Also an update on kickstarter . Not sure on stats? or if video is good advert?

thank you for your interest in the e-ram.

1. The e-ram has a 1:29 eccentric gear, that converts the high rpm of the motor down to a more managable 60-120rpm at the crank.
2. There is a clutch between crank and motor, so the motor can only push forward and disengages completely, once it shuts off. It drives the crank axle directly.
3. We will include an oval chainwheel of your choice in the motor kit, with 28, 30, 32, 34 or 36 teeth.
4. We have not yet decided on any additional warranty arangements, though we will of course meet the standard government requirements.
5. Yes, we will keep spare parts handy.
6. At 120rpm on the crank, the electric motor would be able to put out 270W continuous. The torque at this point would be 21Nm. At lower rpm, we can put out up to 60Nm.

We will probably offer an external on/off switch in future. It will work over CAN bus, so it will be compatible to the first version of the motor. If you have any further questions, feel free to contact us again.

 

[anotherkiwi]

I really like the battery and its plug. Would slip nicely into a pannier or could be bungied onto the rack. Just missing a carry handle or a couple of rings for a shoulder strap.

 

[cwah]

You've got a competitor doing half the weight:
2 kg all included
http://endless-sphere.com/forums/viewtopic.php?f=31&t=68451

However it's a friction drive so less reliable under wet environment and also more noisy

 

[HillyBilly]

"Pendix drive " is the only comparison i have found , more urban in design and not sure what stage in development .Interestingly direct drive crank??
A few more answers from Markus@ Bionicon-
QUESTIONS--
1-To stop pedal 'hitting leg '.does crank torque sensor stop motor instantly?
2-Has battery a charge indicator light display?
3-Which mount type on oval chain ring is used on e-ram?
4-If two chain rings are chosen- Would this work with your oval rings 28 teeth and 36 teeth combination or is this not possible ?
LAST ONE -5- Is routine lubrication needed on eccentric gear drive and is vibration from eccentric felt ?
REPLIES--
1. It only measures the left crank arm, so it might move half a rotation more than absolutely necessary. But it stops quick enough not to be a nuisance.
2. Yes
3. GXP (SRAM standard)
4. oval chainrings are not shiftable (that was why they never were successfull on road bikes. now with 1x11, they lose this drawback). I hope I understood your question correctly, you wanted to mount two oval rings and shift them. You can mount the spider of a regular 2 speed SRAM crank together with a 2 speed front derailleur.
5. The gear is oil lubricated, there is an oil refill port on the motor. Vibration is not felt.