Field Day Mini

Open for any sort of non-technical discussion regarding EVs
Post Reply
User avatar
EV2Go
Senior Member
Posts: 2059
Joined: Wed, 16 Jul 2008, 00:21
Real Name: Paul
Location: Brisbane 1963

Field Day Mini

Post by EV2Go » Thu, 22 Jan 2009, 03:05

Does anyone know if that brown mini from the field day has made it on the road yet? I am keen to know how it performs, from the components it should go quite nicely.

moemoke
Groupie
Posts: 115
Joined: Tue, 20 May 2008, 04:47
Real Name: Andrew Pugsley
Location: Moe, Victoria,

Field Day Mini

Post by moemoke » Thu, 22 Jan 2009, 05:27

I guess you mean this one, on ausmini
http://www.ausmini.com/forums/viewtopic.php?t=42150

In one of the posts there is a link to some video's of it in the testing phase. He is currently needing to raise the rear suspension
as the 150kg battery pack is bit much fot it.
A great conversion with lots of people interested in it
We do not inherit the Earth from our Ancestors,
we borrow it from our Children.

User avatar
EV2Go
Senior Member
Posts: 2059
Joined: Wed, 16 Jul 2008, 00:21
Real Name: Paul
Location: Brisbane 1963

Field Day Mini

Post by EV2Go » Thu, 22 Jan 2009, 18:04

link didn't work, that website appears to have a history of being down Image

moemoke
Groupie
Posts: 115
Joined: Tue, 20 May 2008, 04:47
Real Name: Andrew Pugsley
Location: Moe, Victoria,

Field Day Mini

Post by moemoke » Thu, 22 Jan 2009, 19:24

We do not inherit the Earth from our Ancestors,
we borrow it from our Children.

User avatar
EV2Go
Senior Member
Posts: 2059
Joined: Wed, 16 Jul 2008, 00:21
Real Name: Paul
Location: Brisbane 1963

Field Day Mini

Post by EV2Go » Thu, 22 Jan 2009, 20:05

Thanks for that moemoke... that went like I thought it would... makes me think a bigger engine and rear wheel drive would make a very interesting mini conversion.

fuzzy-hair-man
Groupie
Posts: 118
Joined: Wed, 12 Nov 2008, 16:40
Location: Canberra

Field Day Mini

Post by fuzzy-hair-man » Thu, 22 Jan 2009, 20:54

EV2Go wrote: Thanks for that moemoke... that went like I thought it would... makes me think a bigger engine and rear wheel drive would make a very interesting mini conversion.
You've heard of Twinni Minis? (Twin engined minis) apparently the front subframe will fit in the back Image (with lots of work I expect) or there's rear engined motorbike powered minis in the UK you could borrow rear subframe ideas from.

User avatar
EV2Go
Senior Member
Posts: 2059
Joined: Wed, 16 Jul 2008, 00:21
Real Name: Paul
Location: Brisbane 1963

Field Day Mini

Post by EV2Go » Thu, 22 Jan 2009, 22:23

Yeah I used to own a fairly over the top mini years ago, ported Cooper S head, stroked and bored 1275 out to 1360, nitrided crank, big cam etc. The torque steer was an absolute bitch. That’s why I like the idea of RWD.

Yes I pretty much considered all sorts of weird and wonderful ideas back then including twin engines, I was half way through turboing mine when I gave up the idea because it had way to much static compression.

If I did another mini it would either be a mid mount Warp 9 or 11 with the motor sitting where the back seat normally goes with batteries in the front, or TransWarp 9 or 11 in the front using the tunnel for the exhaust to run a tail shaft to the rear.
Last edited by EV2Go on Thu, 22 Jan 2009, 11:25, edited 1 time in total.

fuzzy-hair-man
Groupie
Posts: 118
Joined: Wed, 12 Nov 2008, 16:40
Location: Canberra

Field Day Mini

Post by fuzzy-hair-man » Thu, 22 Jan 2009, 23:20

EV2Go wrote: Yeah I used to own a fairly over the top mini years ago, ported Cooper S head, stroked and bored 1275 out to 1360, nitrided crank, big cam etc. The torque steer was an absolute bitch. That’s why I like the idea of RWD.

Yes I pretty much considered all sorts of weird and wonderful ideas back then including twin engines, I was half way through turboing mine when I gave up the idea because it had way to much static compression.

If I did another mini it would either be a mid mount Warp 9 or 11 with the motor sitting where the back seat normally goes with batteries in the front, or TransWarp 9 or 11 in the front using the tunnel for the exhaust to run a tail shaft to the rear.


There's some stuff about beam axles in Vizard's yellow book too, the beam axle is supposed to make it handle better (on smooth stuff I think) the pivot point?(not sure that's the term) was quite high so I think the compromises required for transferring drive to a solid diff might stuff up the pivot point??

User avatar
EV2Go
Senior Member
Posts: 2059
Joined: Wed, 16 Jul 2008, 00:21
Real Name: Paul
Location: Brisbane 1963

Field Day Mini

Post by EV2Go » Fri, 23 Jan 2009, 01:06

Are you referring to the diff input pinion angle if I went mid mount? This is generally only a problem if you use a fixed tube diff, the angle of the input pinion can load or unload the rear tyres depending on if the pinion is facing upwards or downwards.

If I did it I don’t think that would be a major concern since I would be looking to use a custom independent rear suspension out of a late model Japanese car with shortened axles.

That way the motor could be basically directly coupled, or through a uni if I used a TransWarp to the independent diff. The slight angle the diff / motor would be mounted at (relative to the car) would keep the motor and the diff in complete alignment.

The negative effect caused by the odd pinion angle would be negligible with an independent rear end as there are no fixed tubes to transfer the torque to the chassis in an unusual way to unload the tyres.

The mini rear end is so simple and with mounting points both in front of and behind the rear wheels, making a custom rear sub frame to suit an independent rear end shouldn’t present any major problems.

Only one potential draw back that I can see... If the diff angle was too great no oil might get to the front pinion bearing.
Last edited by EV2Go on Thu, 22 Jan 2009, 14:10, edited 1 time in total.

User avatar
EV2Go
Senior Member
Posts: 2059
Joined: Wed, 16 Jul 2008, 00:21
Real Name: Paul
Location: Brisbane 1963

Field Day Mini

Post by EV2Go » Tue, 10 Feb 2009, 22:41

In an effort to reduce drive train losses I have been contemplating mounting the Warp 11 east / west in the rear of the mini and driving straight off both ends of the motor.

A few considerations...

Not sure how to put this into words... to reduce side loads and twist on the motor end plate bearings, I am thinking of adding additional plates both ends, that are mounted parallel to the motor end plates and level with the ends of the shafts, so all external CV joint load and flex would be carried by the outboard bearings, kind of like a live axle in drag racing if you’re familiar with them.

I notice most of the Warp motors have different size shafts on both ends, and marginally concerned that the smaller .875” (22mm) shaft may be a bit light on to be trying to drive off it.

Because there is no planetary gears in the motor it would effectively be a locked diff unless I could integrate some kind of LSD into at least one of the axles.

With no gearbox or diff gear reduction would a Warp 11 have enough torque? Granted the 10”, 12” or 13” wheels would help.

User avatar
woody
Senior Member
Posts: 1713
Joined: Sat, 21 Jun 2008, 02:03
Real Name: Anthony Wood
Location: Mt Colah

Field Day Mini

Post by woody » Wed, 11 Feb 2009, 05:16

EV2Go wrote: In an effort to reduce drive train losses I have been contemplating mounting the Warp 11 east / west in the rear of the mini and driving straight off both ends of the motor.

A few considerations...

Not sure how to put this into words... to reduce side loads and twist on the motor end plate bearings, I am thinking of adding additional plates both ends, that are mounted parallel to the motor end plates and level with the ends of the shafts, so all external CV joint load and flex would be carried by the outboard bearings, kind of like a live axle in drag racing if you’re familiar with them.

I notice most of the Warp motors have different size shafts on both ends, and marginally concerned that the smaller .875” (22mm) shaft may be a bit light on to be trying to drive off it.

Because there is no planetary gears in the motor it would effectively be a locked diff unless I could integrate some kind of LSD into at least one of the axles.

With no gearbox or diff gear reduction would a Warp 11 have enough torque? Granted the 10”, 12” or 13” wheels would help.
The smaller shaft would break on a slow, tight corner I think :-) Then you'd have a 1 wheel drive :-)

From memory:
* the Warp 11 generates a peak of 800Nm
* the mini tyres go as small as 25cm radius

This means your peak accellerative force will be 3200N.

Given a weight of 800kg for easy math, this means peak accel of 4m/s/s.

0-100 (~28 m/s) in 7 seconds ignoring drag. So maybe 8-10s with drag.

Most people would be happy with that, but you're not most people.

Should have a decent top speed though, good for a EV land speed attempt :-) You don't need a diff on salt either.

The small tyres don't make up for the lack of diff, kind of like a 1.5:1 diff.

How about a near vertical motor mount above a diff?

Or, You could have 2 9 inch motors, one each direct driving a wheel, this would give you a diff / traction control equivalent and series/parallel switching and 4000N of force.

You'd have to mount them horizontally but at an angle to the transverse so you could fit them both in.

cheers,
Woody
Planned EV: '63 Cortina using AC and LiFePO4 Battery Pack

User avatar
Electrocycle
Senior Member
Posts: 985
Joined: Sun, 19 Oct 2008, 20:23
Real Name: Andrew
Location: Sydney
MSN: dumhed@dumhed.com
Contact:

Field Day Mini

Post by Electrocycle » Wed, 11 Feb 2009, 05:22

yeah I'd go with twin 8" motors running chain or toothed belt reduction to each hub.
Then you just run two controllers, and run a single throttle through a steering angle pot to vary the drive to each rear wheel depending on cornering :)
The Engine Whisperer - fixer of things

User avatar
EV2Go
Senior Member
Posts: 2059
Joined: Wed, 16 Jul 2008, 00:21
Real Name: Paul
Location: Brisbane 1963

Field Day Mini

Post by EV2Go » Wed, 11 Feb 2009, 17:09

Hi Woody,

Can you please explain the math behind your findings so I can try calculate other tyre options.

Couple of questions:

The peak force of 800Nm, what voltage / amps are required to produce that? As in is it really obtainable?

How do you get the 3200N? Is that 800Nm / .25m (25cm radius) = 3200N?

The 4/s/s I am assume is 3200N / 800Kg? That’s means 3200N will move an 800kg car 4 metres in a second right?

0 -100 (~ 28m/s) in 7 seconds (BTW that would be acceptable but would like faster)

I can see 28 / 7 = 4 in there, but not sure how you calculated that

How about a near vertical motor mount above a diff?

No can do... there front pinion bearing wouldn’t get oil. I don’t have any problems with putting the motor in the back seat area.

2 x 9” really isn’t an option due to the weight.

If I use a diff to increase torque I am worried about running out of legs on the Warp 11 as they only seem to efficiently rev to about 3500 rpm

User avatar
Johny
Senior Member
Posts: 3729
Joined: Mon, 23 Jun 2008, 16:26
Real Name: John Wright
Location: Melbourne
Contact:

Field Day Mini

Post by Johny » Wed, 11 Feb 2009, 17:20

If you use a gearbox/diff from a small front wheel drive car (mainly because of small wheels so diff ratio will be lower) as a rear diff the overdrive (or 5th gear) would take care if getting >120k/h before you hit 3500 RPM. Having the gears would then mean keeping the current down to controller-available levels as well.
Direct drive or chain drive from 2 motors on the rear wheels would be a mechanical nightmare IMO.

User avatar
EV2Go
Senior Member
Posts: 2059
Joined: Wed, 16 Jul 2008, 00:21
Real Name: Paul
Location: Brisbane 1963

Field Day Mini

Post by EV2Go » Wed, 11 Feb 2009, 17:44

Only problem with doing that is the lack of space. A mini is very narrow and if I use a gearbox / diff like the brown mini that half inspired the idea, I wouldn’t get the Warp 11 in, he only managed to get an 8” in.

The other consideration is weight distribution I am trying to keep too much weight from hanging off the extremities. If I mid mount the motor and some of the batteries and some batteries up front I think I can get a more favourable distribution.

The motor between the back wheels by itself might not have been too much weight. I got a price yesterday on a Quaife diff (which have lower drag) and might wind up going that way with an alloy 9” diff carrier.

fuzzy-hair-man
Groupie
Posts: 118
Joined: Wed, 12 Nov 2008, 16:40
Location: Canberra

Field Day Mini

Post by fuzzy-hair-man » Wed, 11 Feb 2009, 18:02

EV2Go wrote: Hi Woody,

Can you please explain the math behind your findings so I can try calculate other tyre options.
To make the gearing better (more acceleration) you'd want smaller wheels/tyres that 10 inch which I don't think they exist for cars Image

EV2Go wrote: The 4/s/s I am assume is 3200N / 800Kg? That’s means 3200N will move an 800kg car 4 metres in a second right?

0 -100 (~ 28m/s) in 7 seconds (BTW that would be acceptable but would like faster)

I can see 28 / 7 = 4 in there, but not sure how you calculated that
4m / s / s is acceleration with every second you are able to accelerate by 4 m/s so after 1 sec you are going 4 m/s after 2 seconds you are going 8 m/s after 10 secs you are going 28 m/s
EV2Go wrote: If I use a diff to increase torque I am worried about running out of legs on the Warp 11 as they only seem to efficiently rev to about 3500 rpm
so can you find a diff with a suitable ratio? assuming the mini diff of ~3.14 (to start off) and I'm not sure what rpm it's doing but I'd guess 3500ish at 100km? so with a standard diff it might do about 100km/hr

How fast do you want it to be able to go?

find the speed in m/s, divide this by whatever your wheel circumference might be, gives you wheel revolutions per second, times by 60 to get rpm, now multiply this by the diff ratio to get engine revs. If it's not what your after find a different diff that will fit and take the load and try again...

lets say 150 km/hr = 42 m/s

42 / (2 x pi x.25) = revs /sec
42 / 1.57 = 26.75
26.75 x 60 = 1605 rpm @ wheels
1605 x 2.2 (2.2:1 diff if they exist) = 3531 rpm at the motor

So if I worked it out correctly and you wanted a maximum speed (assuming max rpm 3500) of 150km/hr you need a diff ratio of around 2.2:1, which means with direct drive you'd probably be doing 300km/hr @ 3500 rpm Image
Last edited by fuzzy-hair-man on Wed, 11 Feb 2009, 07:12, edited 1 time in total.

User avatar
woody
Senior Member
Posts: 1713
Joined: Sat, 21 Jun 2008, 02:03
Real Name: Anthony Wood
Location: Mt Colah

Field Day Mini

Post by woody » Wed, 11 Feb 2009, 19:01

EV2Go wrote: Hi Woody,

Can you please explain the math behind your findings so I can try calculate other tyre options.
Sure. My maths for wheel sizes are e.g. 145R10 or 155/75R10.

If the /75 bit is left out then assume /82.

The /75 is the percentage aspect ratio, i.e. tyre profile height / tread width

The 145 or 155 is the tread width (the tyre bulges wider than this) in mm.

The R means radial (not radius).

10 is the rim diameter, in inches.

So the radius of the tyre is (145R10):
half the rim diameter converted to mm: 10 inches / 2 * 25.4mm/inch = 127mm
+
the tyre profile 145mm * 82% = 119mm
=
127 + 119 = 246mm = 0.246m

155/75R10 = 127 + 155*75% = 0.243m

205/65R15 (Commodore) = 15/2*25.4 + 205*.65 = 0.324m

So the difference between the mini wheels and the commodore wheels is 1:1.3, about the same as a 3:1 diff compared to a 4:1
EV2Go wrote: Couple of questions:

The peak force of 800Nm, what voltage / amps are required to produce that? As in is it really obtainable?
It's just from memory, I can't quote a source. Others please chime in here ;-).

A less rubbery figure is that Zeva calculated his MX-5 would put 2000Nm at the wheels, and an MX-5 diff is 4.3:1, so 500Amps -> 400Nm for a Warp 11. I misremembered that was a Warp 9, so the 800Nm is looking like 1000+Amps.
EV2Go wrote:
How do you get the 3200N? Is that 800Nm / .25m (25cm radius) = 3200N?
Exactly.
EV2Go wrote: The 4/s/s I am assume is 3200N / 800Kg? That’s means 3200N will move an 800kg car 4 metres in a second right?
Nearly, it will accellerate it to 4 metres/second in 1 second. So average speed over the first second is 0+4/2 = 2 m/s, so after 1 second, you'll have moved 2 metres.
EV2Go wrote: 0 -100 (~ 28m/s) in 7 seconds (BTW that would be acceptable but would like faster)
Hmm, if it's only 400Nm, then you're 14+ seconds.
EV2Go wrote: I can see 28 / 7 = 4 in there, but not sure how you calculated that.
800Nm accelerates 4 m/s/s, so after 1 second you're going at 4 m/s, 2 seconds: 8 m/s, 3 seconds: 12 m/s, ... , 7 seconds: 28 m/s AKA 100kph.
EV2Go wrote: How about a near vertical motor mount above a diff?

No can do... there front pinion bearing wouldn’t get oil. I don’t have any problems with putting the motor in the back seat area.
Sealed front pinion bearing maybe? (for others).

I think putting it in the back seat area makes sense.
EV2Go wrote: 2 x 9” really isn’t an option due to the weight.
Fair enough.
EV2Go wrote: If I use a diff to increase torque I am worried about running out of legs on the Warp 11 as they only seem to efficiently rev to about 3500 rpm
If someone can give me an estimate the shape of the Warp 11 torque curve with a particular controller + batteries (e.g. flat 600Nm to 3500 rpm and then constant power or power drops off 1/rpm) then I can do a more realistic calc.

The calcs I did in the above post are "You will go no faster than this" rather than "You will go this fast".

A did some playing around in my spreadsheet with flat torque curves: a mini needs at the 155/75R10 wheels:
Nm: 0-100 times
435: 15s
620: 10s
685: 9s
760: 8s
860: 7s
990: 6s

I think the weight and the losses (5-10%) from the diff are more than made up for by the gains (being able to go around corners).

cheers,
Woody
Planned EV: '63 Cortina using AC and LiFePO4 Battery Pack

User avatar
EV2Go
Senior Member
Posts: 2059
Joined: Wed, 16 Jul 2008, 00:21
Real Name: Paul
Location: Brisbane 1963

Field Day Mini

Post by EV2Go » Wed, 11 Feb 2009, 19:06

Ok I need my bike to be able to do 300kph but not my car (that would be dangerous Image )
The tallest diff gears I can get for a 9” is 2.5:1 or 2.8:1 so that would make 1605 x 2.5 = 4012 or 4494 which is still upper side of acceptable.

4m / s / s is acceleration with every second you are able to accelerate by 4 m/s so after 1 sec you are going 4 m/s after 2 seconds you are going 8 m/s after 10 secs (7 secs?) you are going 28 m/s

There must be a point where it can’t sustain that acceleration rate, especially with the torque dropping as revs rise?
Also how would diff gears fit into the formula?

From memory:
* the Warp 11 generates a peak of 800Nm
* the mini tyres go as small as 25cm radius

This means your peak accellerative force will be 3200N.

So if diff gear multiply the torque 3200 x 2.5:1 = 8000N / 800kgs = 10m /s /s that can’t be right can it? That would mean 0 – 100 in under 3 seconds (not that I would complain)
Last edited by EV2Go on Wed, 11 Feb 2009, 08:38, edited 1 time in total.

User avatar
woody
Senior Member
Posts: 1713
Joined: Sat, 21 Jun 2008, 02:03
Real Name: Anthony Wood
Location: Mt Colah

Field Day Mini

Post by woody » Wed, 11 Feb 2009, 19:26

diff (e.g. 2.5:1) has three effects an accelleration:
1. increases wheel torque by the ratio (400Nm -> 1000Nm)
2. decreases wheel torque by the efficiency (~95%) (1000Nm -> 950Nm)
3. decreases wheel rpm by the ratio (2500rpm -> 1000rpm wheel)

10m/s/s to start with, but like you say, it will drop off with higher RPM.

cheers,
Woody
Planned EV: '63 Cortina using AC and LiFePO4 Battery Pack

User avatar
EV2Go
Senior Member
Posts: 2059
Joined: Wed, 16 Jul 2008, 00:21
Real Name: Paul
Location: Brisbane 1963

Field Day Mini

Post by EV2Go » Wed, 11 Feb 2009, 19:53

Thanks Woody for your comprehensive answer. I won’t be using 10” rims, minimum of 12” (factory option) like the LS1275 and would aim for maybe even a 13” with a lowish profile tyre; I think 14” might be a bit too much to ask for.

Since the boot floor pan would be coming out or severely modified to accept the diff and remove factory battery box, it would also receive some mini tubs (pun intended). The centre line of the diff / axle will probably be the biggest influencing factor on rim size.

BTW didn’t need the explanation on tyres Image but will be handy for others that don’t know about aspect ratios.

I should be able to juggle the formulas you have provided to find a workable combination.
Last edited by EV2Go on Wed, 11 Feb 2009, 09:00, edited 1 time in total.

User avatar
EV2Go
Senior Member
Posts: 2059
Joined: Wed, 16 Jul 2008, 00:21
Real Name: Paul
Location: Brisbane 1963

Field Day Mini

Post by EV2Go » Wed, 11 Feb 2009, 19:54

Ok figuring the 12” are 165 x 82 x 12 = 287.7mm radius, the 13” 185 x 70 x 13 = 294.6mm radius. I think 215 x 60 x 14 (307mm) might be a bit more than I can get under the guards.

So using a base figure of 290mm radius, 400Nm from the Warp 11 to get a realistic result, 800kgs for weight (be around that maybe a tad lighter) and 2.8 diff gears.

400Nm x 2.8 diff x .95% efficiency = 1064Nm
1064Nm/.29mm radius = 3669N
3669N/800Kgs = 4.58 m/s/s
28m/s (100kph) /4.58 = 6.11 secs (constant velocity not factoring in drop off)
44.45m/s (160kph) /4.58 = 9.7 secs (constant velocity not factoring in drop off)
28 / 1.82m circumference = 15.38 r/s * 60 * 2.8 = 2583 rpm
44.45 / 1.82m circumference = 24.42 r/s * 60 * 2.8 = 4102 rpm

Just ran the same numbers using 3.9 ratio diff (save me about $3k)

400Nm x 3.9 diff x .95% efficiency = 1560Nm
1560Nm/.29mm radius = 5379N
5379N/800Kgs = 6.72 m/s/s
28m/s (100kph) /6.72 = 4.16 secs (constant velocity not factoring in drop off)
44.45m/s (160kph) /6.72 = 6.61 secs (constant velocity not factoring in drop off)
28 / 1.82m circumference = 15.38 r/s * 60 * 3.9 = 3598 rpm
44.45 / 1.82m circumference = 24.42 r/s * 60 * 3.9 = 5714 rpm

I would have to accept a lower top speed, but without drag and torque drop off being factored in I expect the 100kph time may potentially double.
Last edited by EV2Go on Wed, 11 Feb 2009, 15:14, edited 1 time in total.

Post Reply