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Discussion Starter #1
I am thinking about building a reverse EV trike using a swingarm from a motorcycle. I would like to drive the trike using the existing belt drive already mounted to the rear tire. I would adjust the pulley sizes as appropriate to match the motor capabilities and the normal cruising speed I decide on. Is this a viable setup? I've searched on the forums and could find very little regarding this drive setup. It seems like the most efficient and easiest to do, but I may be overlooking something. If this is a reasonable option, should the motor be mounted to the frame with an idler to maintain the belt tension as on the original motor setup or could I mount the motor to the swingarm so I could eliminate the tensioner by having an adjustable motor base to tighten the belt.

Thanks for any knowledge you can share regarding this.
 

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The general set up works, back in High School I was on a team that built Electron Run (Electrathon) cars in this general form factor. We actually didn't use any suspension at all since the cars were under 100kg and only had 1hp.

Our toughest decision was how much negative camber to use on the front wheels. We were using 20 inch BMX bicycle wheels on all three corners. Which don't handle lateral loading well. If you consider using motorcycle wheels on the front you will need to consider this too.

Otherwise it can work very well!

Sent from my STV100-1 using Tapatalk
 

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Discussion Starter #5
I am thinking that I will mount the swingarm to a Triumph Spitfire frame. Batteries in front where engine would be to try and maintain same weight balance as original spitfire, but with only one wheel in back.
 

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I am thinking that I will mount the swingarm to a Triumph Spitfire frame. Batteries in front where engine would be to try and maintain same weight balance as original spitfire, but with only one wheel in back.
That's fascinating... but why? A car with a missing rear wheel is just a bad car. There have been many trikes made over the decades, but they are all either a poor-handling compromise to dodge some sort of regulations which would apply if there were four wheels, or specifically designed for the three-wheel format... and usually both.

The Polaris Slingshot is a car with only one rear wheel, built that way to avoid safety equipment and other regulatory hurdles for a simple open car; it has a very wide front track (needed to achieve reasonable handling and stability), and some people have been converting them to four wheels!

Because the Spitfire has a sort-of-backbone frame it could be made to work, but placing the swingarm pivot and motor will be difficult, because there's not much length to work with. And of course all of the floor and internal body structure at the rear would have to be removed, much of the trunk would be lost (unless you built "saddle bag" trunks), and it would look really goofy if the outer body were left full-width. Is all of this to avoid having a differential?
 

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Discussion Starter #8
Thank you very much for your input. Like it says, I am a newbie at this.

My reason for a reverse trike was to minimize weight and simplicity of the build if I could use the direct belt drive as I mentioned. I hadn't read anywhere that the reverse trikes handled poorly, so I maybe should reconsider that option.

After looking at the spitfire drive train again, I see that the differential is fixed to the frame, so it should be fairly easy to direct couple a motor to the differential. What are your thoughts on this? I want to eliminate the motor and transmission so I can put the batteries in front to maintain the balance of the vehicle.

So any thoughts or advice on direct coupling to the differential would be appreciated.

My other plan for this vehicle is to ditch the spitfire body and drop on a fiberglass T Bucket body.

Thanks again
 

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My reason for a reverse trike was to minimize weight and simplicity of the build if I could use the direct belt drive as I mentioned. I hadn't read anywhere that the reverse trikes handled poorly, so I maybe should reconsider that option.
Reverse trikes handle much better than one-wheel-in-front trikes, but they are still fundamentally limited. When cornering there must always be load transfer from the tires on the inside of the turn to those on the outside, to counteract the leaning tendency due to the cornering force at ground level, below the height of the centre of mass. With a trike, all of that transfer is done by the tires at one end of the vehicle, which is both too much for them, and unbalanced. There's a reason that vehicles of this format (even "reverse" or "tadpole" style) are generally wide and very low (improving handling) or very low performance (so handling doesn't matter).

The BRP Can-Am Spyder is a reverse trike with the rider sitting way up on top of it, but it is ridden like a snowmobile... the rider leans into the turns. Even it is very wide for a vehicle without side-by-side seating.

To be fair, the recently sort-of-started-production Solo from Electra Meccanica is a reverse trike, and not exceptionally low or wide, or slow. Despite the maker's promotions, I don't think anyone seriously expects good handling from this vehicle, which is a variant of the old Corbin Sparrow design (the fourth one to go into production).

The simplicity of the belt drive is certainly desirable, but conventional automotive differentials and shafts are readily available and already worked out; that's why I wouldn't put a lot of value on eliminating them. If you had to build everything from scratch, it would be a very different matter - that's why some old and third-world three-wheelers were and are still built that way.
 

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After looking at the spitfire drive train again, I see that the differential is fixed to the frame, so it should be fairly easy to direct couple a motor to the differential. What are your thoughts on this? I want to eliminate the motor and transmission so I can put the batteries in front to maintain the balance of the vehicle.

So any thoughts or advice on direct coupling to the differential would be appreciated.
There isn't really any space for an adequately large motor immediately ahead of the Spitfire final drive (differential), but you can put the motor where the transmission is normally located, leaving the entire engine space available for the battery. With only the final drive ring-and-pinion gearset between the motor and the wheels for speed reduction and torque multiplication, this is a relatively low-speed motor application, so adequate performance needs either a relatively large motor (which is hard to fit in the narrow transmission tunnel) or a single-speed reduction gearbox on the end of it (relatively simple, but a specialty item so very expensive).

There are 11 Spitfires in the DIY EV Garage. It appears that all of them either use a transmission (either the original from the Spitfire or similar), or are incomplete, or both.

A motor without a traditional transmission is certainly possible. One of the best known examples in this forum of this configuration in a similar size and configuration of vehicle is Duncan's "Device". He used a large motor - larger than that used in the Spitfire projects - and was able to fit it in because he custom-built the frame, rather than working with something like a stock Spitfire frame. Duncan's motor is further rearward than a typical transmission, but it's basically the same configuration. The Spitfires usually use a 9 inch diameter brushed DC motor; Duncan used the same type of motor, but 11 inches in diameter.

This gearing issue can be addressed in some cars by choosing a different final drive ratio: some final drives (differentials) have ring-and-pinion gear sets available with various ratios, from less than 3:1 to more than 5:1. Unfortunately, for the Spitfire the most extreme reduction ratio is probably 4.11:1, which is the same as or not much better than what you already have (likely either 3.89:1 or 4.11:1).
 

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My other plan for this vehicle is to ditch the spitfire body and drop on a fiberglass T Bucket body.
By the time you have discarded the Spitfire's engine, transmission, and body, all you have left is a frame which is not really appropriate for a T bucket body, and a suspension which was designed in the 1950's. The Spitfire chassis was pretty good for the 1960's, and great fun to drive (we have one), but pretty crude by today's standards. It might make more sense to sell the Spitfire to someone who actually wants one (there is still lots of enthusiasm for them), and find a more suitable chassis.
 

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Hi
A Spitfire would make quite a nice machine

Put the motor where the gearbox would normally live

http://www.diyelectriccar.com/forum...dubious-device-44370p15.html?highlight=duncan

The device uses Subaru bits so it is a good bit larger - but it's the same idea

I'm using an 11 inch motor - because I had one! a 9 inch would do just as well

Not sure about a T bucket body

I like the "Hurricane" a replacemnet body for the Spitfire
https://www.google.co.nz/search?q=h...=RYSwWY_2AYzJ0gSFvaqoDQ#imgrc=hJVYBlemtBQ-IM:
 

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Discussion Starter #13
Thanks everyone for your thoughts, recommendations and support. If I put the motor where the transmission goes, do I just get a special driveshaft made?

If motor is coupled to differential, will I have enough torque with an AC motor or should I consider DC? I realize AC is more costly, but it seems the benefits are probably worth the extra cost. Thoughts?

I do not have a spitfire donor yet, but it's the only vehicle with a frame that looks like I can just drop the T bucket body onto. I've always wanted a T bucket and am also a fan of EV, so I decided I should combine the two thoughts. But, I also want to do this on the cheap. I'm hoping to find a spitfire donor that I can use the chassis and part out the remaining parts to keep my project costs low. I'm looking for economy, good range and hopefully something that catches attention, I don't need a race car.

Thanks again for the feedback.
 

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Put the motor where the gearbox would normally live
...
I'm using an 11 inch motor - because I had one! a 9 inch would do just as well
An 11 inch motor won't fit there in a Spitfire - even a 9 inch might be tight - and that leaves the question of whether a 9-inch really would be suitable with only the final drive reduction.

If I put the motor where the transmission goes, do I just get a special driveshaft made?
The electric motor doesn't have a shaft end to which you can readily attach the motor side of the joint that you will need at the front of the shaft. I don't recall how Duncan set up his, but look at his build thread for one possible configuration.

An off-the-shelf solution is the TransWarP motor style from Netgain (the 9" model is the TransWarP 9) - they build the motor with a shaft end to which the driveshaft can be attached, and add a housing like the tail of a conventional transmission, with suitable bearings in the housing.

Whatever is done at the output of the motor, you would be having a custom driveshaft made up with the stock Spitfire (or whatever chassis you eventually choose) joint on the rear end and something else on the front end; this is not a problem because there are shops which do this sort of thing routinely.

If motor is coupled to differential, will I have enough torque with an AC motor or should I consider DC? I realize AC is more costly, but it seems the benefits are probably worth the extra cost. Thoughts?
With a typical DC motor (such as the common 9" size already mentioned), I don't know if you would consider the torque to be "enough". A motor with 100 lb-ft of torque (NetGain's spec for their WarP 9 / TransWarp 9) directly driving the diff would deliver about the same torque to the wheels as a stock late-year Spitfire engine in third gear... and you can't shift down to get more torque to the wheels at low speed. The pace of acceleration would be quite "relaxed". A higher reduction ratio in the diff, a motor with higher torque output, or just driving that size of motor harder (more voltage, less reliability) could improve performance.

I note that none of the 11 builders or prospective builders in the DIY EV Garage have gone ahead without a transmission, although Baratong built a no-transmission adapter, before reconsidering and going with a transmission. The 9" motor didn't really fit in Baratong's Spitfire; the entire transmission tunnel had already been hacked out by the previous owner, and in the test fit the WarP 9 still protruded into the engine compartment. If you decide to go without a transmission, perhaps Baratong still has the hardware he built, and would sell it to you... if you go ahead with a Spitfire chassis.
 

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Nope
Torque is proportional to current
If you want more torque - apply more current!

The Device is about the same weight as a Spitfire with more weight on the rear wheels plus wider tires and an LSD
And I can smoke my tires!

A 9 inch will give a bit less torque than my 11 inch - but I drive on the road at 50% power because 100% is too scary!

The advantage of a 9 inch is that it can do more revs!

As far as fitting is concerned I think the Spitfire has a cardboard transmission tunnel - so it can be enlarged quite easily
 

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Nope
Torque is proportional to current
If you want more torque - apply more current!
... and to get that current to flow, apply more voltage. :rolleyes:

A 9 inch will give a bit less torque than my 11 inch - but I drive on the road at 50% power because 100% is too scary!
Three-quarters of the 11" torque, using NetGain's specs for their 9" and 11" motors.

The advantage of a 9 inch is that it can do more revs!
NetGain lists the same maximum speed (5800 rpm) for its 9" and 11" motors, but sure, in general a larger-diameter motor will be limited to lower speeds.

But even if the smaller motor can turn faster... so it has a theoretical top speed even further beyond the speed at which the vehicle will ever be driven? With fixed gearing which is too tall anyway, I don't see how the availability of higher motor speed does any good.

As far as fitting is concerned I think the Spitfire has a cardboard transmission tunnel - so it can be enlarged quite easily
It has a steel transmission tunnel, but it isn't very structural (it's a body-on-frame vehicle) so it can certainly be modified. But then, anything can be modified, for a price and with enough time. Since I have both of my legs, I wouldn't want a wider transmission tunnel in the Spitfire.

Of course, if using only the frame, this isn't an issue. :)
 
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