# Electric motors housed within the rear axel ?



## Woodsmith (Jun 5, 2008)

It can be done but my first concern would be the unsprung weight and the vibration to the motors.

You may be better off putting a motor in the transmission tunnel and keeping the prop to the original axle, a Transwarp9 for example may be fine.

An alternative might be to fit an IRS system but that would involve a lot of engineering and may not give you any weight benefit for the complexity of the conversion.


----------



## MartinD (Jun 13, 2011)

Thank you. I do understand and agree your point about unsprung weight, even if vibration could be lived with.
Please excuse my ignorance, but what is an IRS system ?


----------



## major (Apr 4, 2008)

MartinD said:


> Please excuse my ignorance, but what is an IRS system ?


IRS is the Internal Revenue Service. Don't you pay tax 

Seriously, I think Woody was referring to Independent Rear Suspension.


----------



## Woodsmith (Jun 5, 2008)

major said:


> IRS is the Internal Revenue Service. Don't you pay tax
> 
> Seriously, I think Woody was referring to Independent Rear Suspension.


Cheers major,
Not been well so posting quickly and sporadically. I should have been clearer.


The other reason for not building the motor/s into the axle assembly is to keep things simple and servicable and using common and accessible parts for future servicing and upgrade.
The big space ahead of the axle could be better used for part of the battery pack, as can the now empty engine bay and fuel tank area under the boot floor.


----------



## MartinD (Jun 13, 2011)

major said:


> IRS is the Internal Revenue Service. Don't you pay tax


Sure I know about tax. In the UK it is 60% the cost of fuel. Every time I fill up my diesel 4x4 I receive another kick in the direction of converting my old MG to electric that has now sat in the garage unused for the last 9 years….
Thank you guys for putting me straight on the powered axel idea.


----------



## Yabert (Feb 7, 2010)

MartinD said:


> The whole of the engine bay is then available for batteries + controller etc


That is a really good idea. You can try to mount the motor close to the rear differencial, in the drive shaft tunnel or mount in the rear of the car (something like an old VW beetle).

But the controller need to be close to the motor. Keep this in mind.


----------



## Woodsmith (Jun 5, 2008)

The MGB tunnel gets very narrow at the back end. There may only just be room for a 9" where the gearbox used to live and even then it might need opening up a little to fit it. That is where I would put it though and retain the propshaft to the axle.
The controller can then go in the engine bay near the motor.

With UK restrictions you'd want to try not to cur any of the body shell is you can as it can cause IVA issues. The fuel tank is fairly shallow so it may limit the batteries underneath, and over, the boot floor unless you want to fit prismatic lithiums on their side or make up a small pack to fit using cylindrical cells.

Whereabouts in the UK are you, Martin? I'm in Manchester and there is a growing EV community in the UK which is nice.
You can add your location in your profile.


----------



## MartinD (Jun 13, 2011)

I still cling to the idea of directly driving the rear wheels from a pair of motors mounted between the wheels, mainly to cut out as many unnecessary bits of (heavy) 40 year old car as possible. I believe it is possible to design a way to mount the motors to the chassis with flexibility in the drive/mounting to allow for suspension movement. There should be the space to do this as the existing batteries are in this area, basically under the rear seats, should a car like this have rear seats. Ideally no cutting about of the body.

I take the point of distance to the controller, but is that not down to wire size?

Issues for me are motor spec and controller spec as I would guess there needs to be some logic or balancing between power and speed of the two motors.

My apologies for not filling in the profile. I am near Hitchin & Bedford (often in Norfolk) and very new to the EV conversion game, but finding this all rather fascinating. Part of my profile should say that I always find a different way of doing things (that is what the “D” stands for), but will always listen to advice…

If the twin motor idea is not practical, I will happily go back to the single motor idea as suggested.


----------



## Woodsmith (Jun 5, 2008)

If you are determined to try the twin motor route then you will need to find the motors you might be able to use first. That will determine how and if they will fit and how much space is left for drive shafts.

You could look at the Agni 95R as a possible motor. Talk to Steve (Jozzer) at Jozztek as he had some recon units. He will be able to advise if two would be sufficient for the MGB.

You might find that motors that will fit may be a bit low on power and/or torque.

I don't think the original axle will be that much of a problem weight wise even given the MGB wasn't a light car to begin with. Don't forget the added weight of changing the suspension, adding new mounts and location points and all the IVA issues that brings up. Building a solid beam axle with the motors in may be a bigger weight penalty and could raise lots of alignment issues too.


----------



## Woodsmith (Jun 5, 2008)

The issue of controller to motor location is to do with the very high current that goes between the two.

Even using a high voltage pack the controller will reduce the voltage and increase the current to control the speed. You can have cables from the pack to the controller to handle the controller input current but the output will need to cope with more current.
You can just use bigger cables but you will get more losses as well as using more money for the bigger cables.

It is easier to put the controller in the boot if you are having the motors in the axle as that will be the closest point.

Another point to consider is the big heavy cables to the motors being shaken up and down by the suspension.

All in all I see little benefit from a motorised axle but if you can build one that overcomes all the downsides then why not. It would be good to see.


----------



## RedBandit (May 27, 2009)

I've wanted to do something similar for years. As it turns out I don't have any time to do anything at all, regardless this has been my desire for a while now. 

My hope was to drive the axle with a single motor and maintain a more or less stock differential, but it would probably still require some regearing. I think most of my ideas require more custom work than I can afford at the moment so I haven't gone anywhere. I guess I don't have much to contribute other than my moral support. Good luck, I hope you have progress we lurkers could follow.


----------



## MartinD (Jun 13, 2011)

I came across Agnimotors before I came across this forum, after following up on Cedric Lynch who I saw on TV and had been recommended to me through the boat building world (yes, I also want to build an electric boat). I had a reply to my initial enquiry, but have not had a reply after providing further information. However my conclusion is these motors, although highly desirable, are very much underpowered and many more than 2 would be required. Fine if you want to build a motorbike.
I am however fast coming to the conclusion I need to heed some of your advice on single motors though.
I have had a look at the Transwarp9 but wonder if there is a link for UK supply?... http://www.go-ev.com/ Claim to be is the exclusive worldwide distributors.


----------



## Woodsmith (Jun 5, 2008)

I think the Transwarp9 is going to be an import. There was one on Ebay a year or so ago that a converter was selling, it went for about a grand IIRC, I bid £700 for it and didn't get it.

You can use a forklift truck motor and just adapt the shaft to a UJ flange that fits the MGB propshaft. It shouldn't be too difficult for a machine shop to do. Even a propshaft maker/repairer could probably do it.

Some fork truck motors have a propshaft flange already on them, to drive a short prop to the truck's axle. Others have the motor on the axle and are gear drive. If you go for this type get the gear if you can as it can be machined/converted to a flange.

Be careful of motors that have a female shaft. If you can get the splined shaft that fits it then you might be able to convert that to a UJ but it isn't simple.

The easiest motor would have a plain parallel shaft with a keyway, that will couple easily to most things.

Here's a link: Fork Truck Breaker in Chesterfield. They have a warehouse full of motors at about £300 each.

However, starting at the begining, take the MGB engine and gearbox out and then measure the space available in the tunnel. You can make up a 9" cylinder from cardboard, about 15"-20" long to see if it can be fitted, you may need to beat out some of the tunnel sides or go for an 8" motor.


----------



## MartinD (Jun 13, 2011)

It strikes me there are a lot of similar one off projects going on, each with issues of cost, supply and availability, but each finding their unique solution.

For me, I am not into building a scrap heap challenge out of salvaged parts, but resolving all the issues in a reliable and repeatable way.

Is there a case for those interested in EV conversions getting together in an area or country basis, pooling resources and negotiating better deals on quality parts?... Take it one stage further and you consolidate imports, so making a huge saving on freight etc.

Perhaps a subject for a new thread.


----------



## Woodsmith (Jun 5, 2008)

Very occasionally groups do get together to make group purchases of parts, usually batteries, to reduce costs.
Sometimes this works, sometimes it doesn't. The difficulty, in the UK at least, would be that there are not that many of us and we are all at different stages of build.

I have decided against the new components direction to aim for recycling as much as I can while also keeping costs down. That isn't everyones choice but just one option.

Sometimes relaibility isn't down to new parts, though repeatability is. A good used motor is as reliable as a new one if treated right and properly serviced.
A very reliable controller with a good reputation would be the Soliton 1 and also the Open Revolt kit. Some other controllers have had some poor press while others have been around a long time.
I am using preused controllers until I can build an Open Revolt.

Building out of salvaged parts isn't a huge issue really, your whole car is a 'salvaged part' in one respect where as mine will be a new build using salvaged steel.

Are you looking at converting more then one car? If so then that would be a good new thread.
I would suggest that if you are looking at a UK group buy it may be worth having a look at The Battery Vehicle Society as a UK forum. There are many there who are not here, but are here in the UK, if you see what I mean.


----------

