2:1 reduction gear ideas?

[Mouse]

Anyone got any practical ideas about how to achieve a 2:1 reduction to reduce the motor rpm / multiply the torque before going into a final drive?
It's for a Outlander MGR, 60kw.

[rstevens81]

if you have the manufacturing capbilities avialable, you could probably reuse a toyota prius transaxle planetry gearset, if you hold the planets in place you will get a 2.6:1 ratio between -mg1:mg2. In a similar place myself trying to decide what to use when my conversion gets moving (car gearbox vs outlander mgr diff thing vs something else like this).

For some reason I thought you were doing a bike then all you would need is a really big cusom made sprocket (laser cut)?

see: http://eahart.com/prius/psd/ (you will need flash to make it work, but it lets you play with diferent speeds on mg1/mg2/engine)

[ZooKeeper]

Low Range transfer case planetary?

[Mouse]

For some reason I thought you were doing a bike then all you would need is a really big custom made sprocket (laser cut)?

Yea I am doing a bike but I want to avoid a chain final drive if at all possible. This is for various reasons but mostly because chains are short lived which makes maintenance expensive and tedious. I gave up with chain driven bikes years ago because of it. The big plan is to use the electric bike for my primary transport and as I currently do about 20000 miles a year and have only ever got about 8000miles per chain + sprocket set it's a thing that soon adds up on the maintenance bills.

Low Range transfer case planetary?

Sounds like a worthy consideration, as is the toyota prius transaxle planetry gearset, however I have no real idea what else they are fitted to for scavenging parts from.

I've kind of settled on the BMW K series swing arm and beval drive as they are available in a range of ratios and are reasonably plentiful on the 2nd hand market but I'll be needing a further reduction before this.

First idea simply connecting to the drive shaft. Max reduction from available ratios is 3.36:1 which gives a max wheel speed at max rpm of about 202mph using 9000rpm as a maximum for the outlander motor. This is clearly ridiculous. Only the lowest rpm from the motor is usable and the toque to the rear wheel is heavily compromised by the high gearing.

Second idea using two final drives in succession. lowest reduction is 2.82 X 2.82 = 7.95 and a max wheel speed of about 86 mph which is lower than I'd like it, not that I'm a speed freak but being able to hit 100mph would be good plus I'm guessing having the motor near max rpm in normal use will compromise available torque as the motor will be tapering off at this speed.

Third idea is using a reduction of 1.59 from an Audi TT transfer box. 1.59 X 3.36 = 5.34 and a max wheel speed of about 130mph, which again is still a bit high but closer to what I'm aiming for.

Ideally I want a max speed to be around 100mph for best acceleration and lower gearing but not so low the torque of the motor will be tapering off as it reaches max rpm during normal road use. This I think needs a ratio of about 6:1 which I can get using a reduction of 2:1 followed by the bevel drive of the swing arm of 3:0:1

Mind you it's mostly guess work at this stage so please chip in if I've made any really bad assumptions.

[rstevens81]

I wouldn't give up on option 1 yet... How much power do you want from a bike at what speeds, remember weight is thy enemy! (& Keep it simple).

If you look at the Mitsubishi imeiv evolution that was used for the pikes peak challenge they pumped out 300nm of torque per motor (these were modified motors whos speed was increased to 11krpm) it gives and indication of the potential.

If I remember right you were considering 4x 16s BMW modules so you could potentially have 236v nominal if you push say 260a (I believe 200a is about stock Outlander at 195nm, & Damien has breifly pushed 100kw out of his 96s pack, so should be achievable at least for short pulses) out of the batteries that would give you 60kw (minus losses).

Baseed Dyno curves for the imiev (https://forums.aeva.asn.au/viewtopic.php?t=3031) the power goes flat line (which if we assume when Fw is applied, this could be wrong as found out with the leaf motor) at 3000rpm on a 88s battery.

Then based on 64/80 you would get max power between 2400-4800 which based on your calculations above would be 2400/9000 * 202 = 53 mph (to 103 mph)

Remember you are going to getting based on the above 260/200 * 195 * 3.36 = 852nm at the wheels from zero to 50mph that seems like quite alot if torque on a bike to me!

Edit: third idea would give max power from 33mph to 66mph and give you 1354nm at the wheels (till 33mph)


Sory got mixed up it was clanger9 who was using the BMW batteries but most of it still stands as torque is king.

[bexander]

VW Golf II and III Syncro might have other gear ratios than the Audi TT on there transfere case.

[Mouse]

VW Golf II and III Syncro might have other gear ratios than the Audi TT on there transfere case.

After a quick search they all appear to have the same part number across the VW/Audi golf and TT ranges which is a shame but worth considering.

I had no idea the motors were comparable in the Mitsubishi i-meiv, not sure how beneficial that is but useful to know.

I have BMW i3 96Ah 12s battery modules. I found out after getting them that they are the same modules used in the BMW electric motorbike.
Still looking for a working and affordable BMS solution as the BMW protocol doesn't appear to have been cracked properly to allow balancing yet.

How much power do you want from a bike at what speeds, remember weight is thy enemy! (& Keep it simple).

All the power!! What fool wants only some of the power?
I'm after useable road speeds, commuting, motorway etc with enough in reserve to be a bit of fun.
Understood about weight but the current bike has a VW 1900cc TDI engine and car gearbox in it and is a real heavy weight. I could probably use all 8 battery modules and be of comparable weight

I've just had a closer look at this dyno graph tucked away in another thread here and it lists the torque as starting at 277nm and dropping to 195nm max ev speed of 135kph, 84mph. The rpm on this graph is clearly garbage and I've compensated for that using the standard issue wheel diameter and transaxle reduction gear to 277nm @ 1780rpm and 195nm @ 6870rpm. This is consistent with the max rpm of the motor of ~9000rpm and the max speed of the outlander listed as 110mph.
Not sure how seriously to take the torque readings from this source as they are selling a performance enhancing module and probably prone to exaggerating.

[jap]

the current bike has a VW 1900cc TDI engine and car gearbox in it

We need pics or something

[Mouse]

[We need pics or something

You might need a stiff drink after seeing this

I've done a talk about it at a hacker camp and recently done a walk around video if you're interested.

[rstevens81]

I think my first car was lighter