Lotus Elan

Introducing myself - eejit with an electric car project

PostPost by: Own Little World » Thu Nov 05, 2015 8:11 pm

Dear all,

I would like to introduce myself as a new member to this forum (and lurker for a couple of weeks).

I have been owning, loving and restoring MGB Roasters for over 20 years and admiring Elans from afar. I have also been planning an electric restoration of some sort of sports car for a while now and the following occurred to me::

1) I ideally needed something lightweight - lighter than a B
2) I wanted something with 2 rear seats (for the littluns)

When I saw a +2 on ebay going without an engine or transmission and with a rusted through fuel tank it looked like a perfect donor and I went for it. (Actually I have since decided to use a multi-speed transmission for added efficiency, to which end the seller was also kindly able to supply me with an MT75 box).

I have found a couple of threads on this forum so far, relating to similar projects and I was wondering whether any members have made progress since then and would be happy to share their experiences.

I am currently looking at the AC Induction motors, something like a HPEVS AC-76 motor. I am less sure about the controller but I am looking at things like the NetGain WarpDrive. I imagine that the project will probably take a year or two, given all my other commitments and therefore I will leave the battery purchase to the very last minute, just in case there are any battery tech quantum leaps between now and then.

My general design parameters are:

1) 100-150 mile range at sensible A-road speeds (cf. the "New European Driving Cycle").
2) Enough grunt still to do the Elan justice (at least for a few minutes of fun)
3) Final curb mass no more than ~1000kg (MGB territory) so as not to lose too much of the famed Lotus handling.

I am also looking at ideas to add lightweight strength and safety the fiberglass tub (maybe I will leave that to another thread though...)

Hopefully speak soon,

Alec
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PostPost by: Own Little World » Thu Nov 05, 2015 8:56 pm

Dear Moderators - I realise this should maybe be in the "introducing myself" or even the "mods" section.

Please feel free to move as appropriate.

Thanks,

Alec
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PostPost by: Mazzini » Thu Nov 05, 2015 10:21 pm

Welcome! Makes a change from the Zetec mob :D Good luck with the project!
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PostPost by: trw99 » Thu Nov 05, 2015 10:51 pm

Welcome Alec.

Clearly you are going to shock us all with your current plans. All sounds rather hair-raising.

Toddling off now ...

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PostPost by: billwill » Thu Nov 05, 2015 11:49 pm

Why would you need a multi ratio gearbox with an electric motor ?
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PostPost by: Europatc » Fri Nov 06, 2015 12:32 am

welcome Alex
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PostPost by: prezoom » Fri Nov 06, 2015 3:51 am

A good friends son owns EV West, and they have done quite a few electric motor conversions. As far as transmission choices, the 3 Series BMW they did, used a two-speed Powerglide transmission. I can tell you it works great. Acceleration is amazing, even with a very heavy car. They took that car to Pikes Peak a couple of years ago and finished 4th in class, despite having the only non-purpose built car in the class. Lately they have done a Factory Five 818 and a 308 Ferrari. Can't wait to get a ride the Ferrari......... his dad has promised.
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PostPost by: john.p.clegg » Fri Nov 06, 2015 9:08 am

Alec

Whereabouts in England?

Sounds like a good project,keep posting as it progresses...

John :wink:
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PostPost by: Own Little World » Fri Nov 06, 2015 11:27 am

Hi everyone - many thanks for the warm welcome.

John, I am just outside Hastings on the South Coast. I should change my profile to be a bit more specific.

Billwill, I have been reading that although the Torque curve is pretty much flat with an electric motor, the efficiency curve isn't. They say that with a multi speed transmission (by that they usually mean 2 or 3 gears, not necessarily 5) you can increase the range by 10-15%, even when you factor in the mass and transmission losses etc.

Also, the 5th gear on the MT75 is overdrive, which should mean less revs and current at motorway speeds. Not that it will really be a motorway car though.

Prezoom, the EV West website has been my main point of call for component specs as they seem to have a stocklist much longer than anyone elses. They seem to be the godfathers of EV so I will give them a call soon.

The Ferrari sounds very interesting - the 308 was fiberglass too, wasn't it?
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PostPost by: 661 » Fri Nov 06, 2015 11:40 am

Good luck with the build. Sounds interesting, put up a build thread.
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PostPost by: Elan 1600 » Fri Nov 06, 2015 11:46 am

Hi Alec or is it Alex

There used to be a guy in Peacehaven who ran an electric MX5. You can read a bit more about it at https://endless-sphere.com/forums/viewtopic.php?f=34&t=38171.

All the best with your project
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PostPost by: john.p.clegg » Fri Nov 06, 2015 12:02 pm

Alec

Shame you're so far away,would have loved to "poke my nose in ",keep us updated...

John :wink:
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PostPost by: Own Little World » Fri Nov 06, 2015 2:35 pm

Thanks again for the comments, and I look forward to hooking up in person in the future.

I will certainly do a build thread but I expect this to be a long haul.

The donor car has seen better days. I think it may have had a family of ducks as previous tenants as it has full of feathers, snail shells and an unforgettable smell. However, I am used to seeing through these things, a an MGB addict.

In fact, even before I start on the +2, my first priority is to smarted up the paint on the Roadster. I will have to sell it (after17 years) to fund the Lotus project. Sniff.

It will all make sense in the end though.
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PostPost by: Bombay Racing Green » Sat Nov 07, 2015 2:20 pm

Hi Alec,

Welcome. I'm glad you brought this up. I was looking at the very same thing myself and would be very interested to see how you get on. I'm sure you have looked at the various YouTube videos on the subject. I found that the EVTV programmes to be filled with information and advice. A look through their project data base is inspiring. My personal favourite is the Beck Porsche 904gts conversion. It used a DC motor but everyone is moving to AC motors now. Another good site with tutorials is EV4U.

Some things that I came up with whilst pondering this kind of project:

The HPEVS AC50,I think, will give more than enough oomph for the +2. The netgain controller I think is more suited to netgain DC motors. Most of the packages I looked at (for example on www.thunderstruck-ev.com) have a matched AC inverter for the AC motor.

The most conversions retain the original gearbox and only use reverse and the higher gears. The lower gears will just result in dramatic wheel spin. The clutch is also retained as an added safety precaution ie the motor can be disconnected in case of a runaway controller ( I think that's not so much a problem with AC motors but is with DC ones). I did think of doing away with the gearbox altogether and connecting straight up to the diff but after seeing a tutorial on EVTV decided against this. You will need quite powerful motors that, whilst needed to get moving, will be wasted during the cruise. The EVTV programme describes this better than I can. I realise Tesla are doing this but again I will refer you to the tutorial!

Battery packs, size and placement. A tutorial on EV4U gives you a handy way of calculating range and pack size. I too would like to get the range that you specified as my commute is exactly 100 miles round trip. The pack size (and hence pack weight) would be very large. Too large I fear for the +2. Bringing the range down to say 75miles will require 44 x 180ah CALB type batteries I seem to recall. That would give me the 50 miles to work with a useful reserve and there are changing points available whilst I'm at work. You could split the pack and puts some in the engine bay on top of and around the motor and one where the petrol tank is. You might still be able to retain the rear seats. The issue I can foresee is how to securely attach the pack (mounted in a metal cage) to the chassis. The backbone of the chassis is relatively narrow. Perhaps a combination of bottom attachment to the chassis and lateral attachment to the rear uprights? I dread to think what an unsecured pack of that size would do in a rapid deceleration especially if you have the kids in the back. Putting part or all of the pack in the front will put a huge load up front. The front springs will have to be able to cope with this. The boot (trunk) is of no use as the fibreglass construction will just cave in! Also a Spyder chassis MAY be of more benefit than the Lotus one. Perhaps a call to Spyder may help you. They might have done one already!

I apologise if this has thrown up more questions for you than answers. I certainly think that it is a worthwhile engineering project. It will certainly take the Elan in a whole new direction. To allay the fears of the purists, as most conversions retain the original transmission and differential the car can be returned to normal specs relatively easily. I was also eying up the Europa for a similar conversion but at 6'2" in height I simply don't fit! Other than that it certainly looks good as a conversion. Aerodynamic, a large engine bay and light weight.

Don't let any of this put you off! I would love to see it turn into a reality. I believe that all the issues that I have mentioned can be overcome successfully given sufficient time (and money!). With three kids under three I don't have either! A recent Kit Car magazine had an article on an all new EV seven type. Also this chap in Canada (www.szott.com) has done a Lotus 23 type EV conversion.

Good luck and keep us posted.

Regards,

Pete.

PS. As always, I am standing by to be corrected on any of the above.
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PostPost by: Own Little World » Sat Nov 07, 2015 5:44 pm

Hi Pete,

Glad to meet you.

I am sure I remember reading on one of the sites that the Net Gain controller was suitable for a variety of motors, including induction, but I have just looked at EV West and it is not stated there, so you may well be right. I looked at the various matched Curtis controllers and they all seemed to be limited to about 500 Amps.

I was thinking of a slightly higher voltage than 44 cells - I was thinking more like around 50 x 160Ah and that was coming out towards the top end of if not more than my mass budget.

My range calculations are not based on any prior experience of EV conversions, rather:.

1) Calculate the theoretical range of the Tesla Roadster for the European driving cycle, based on published vehicle specs
2) Divide the theoretical range by the published Tesla range for NEDC to get a scaling factor
3) Calculate the theoretical range of the Lotus for a variety of configurations
4) Apply the scaling factor to approximate the real life range.

The theoretical calcs were done by calculating the total energy expended against wind resistance and rolling resistance at the mean driving cycle velocity and due to acceleration at the mean driving cycle acceleration minus a small amount of saved energy from regenerative braking. In the best circumstances I was hovering around the 100 miles point.

I was aiming to completely fill the area where the fuel tank was and place the rest in the engine bay, as far back as I can. I think I fit within the overall volume envelopes, maintaining a similar mass distribution but I have not worked out the exact orientation and configuration of the cells. I am also thinking about making up a frame, like yourself.

What sort of performance do you reckon to get out of the AC50? Are you thinking 96V or 144V?

Thanks for the site recommendations, by the way.

Speak soon,

Alec
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