EV from Scratch Build Thread - Please feel free to contribute!
 

Off and on over the last few months I have posted that I was going to design and build my own EV. Well finally things are coming together and I have made some decisions based on practicality.

The vehicle is going to be a 3 wheel design with a minimum speed of 75 mph and a range of 80+ miles (will probably go for 100+....all depends on my budget, the battery pack will be scalable)

I have created a blog charting my efforts and designs and already includes some designs that I am working on in SolidWorks. You may recognize the design because it will be based on the Australian TREV. However I do plan to improve its aerodynamics significantly.

Here is a sample image of what I have so far:

IsoViewFullCarVer2 - Vox

The main information/advice I need right now is regarding the suspension and steering system. I am estimating the total weight including driver to be around 700 pounds at the moment (could be as low as 450 though). Also need to learn about breaking more. I am hoping to not need any hydraulics for braking pressure (hopefully that would be unneeded weight/complexity).

The plan is regenerative breaks from the rear wheel and mechanical brakes of sort on the front. I also need to figure out a way to have the mechanical brakes to only kick after a certain amount of force is applied to the pedal so that the regenerative brakes do almost all braking except during emergencies.

Please check out my blog: BenW’s blog - Vox

3 wheels will be interesting for a DIY build, I look forward to seeing more, be sure to keep us up to date!

Looks good so far. I'd maybe look into motorcycle brakes for something that is mechanical and built to stop something with the weight you're looking at. Probably not a bad place to start to look for suspension stuff too.

I would recommend that you consider just using a VW Beetle/Thing front suspension. It's a torsion bar setup which is fairly lightweight.
http://www.vwtrendsweb.com/features/...Suspension.jpg

I don't think I need something as heavy duty as that. I need to be very weight conscious for performance reasons. The battery pack will be the primary cost of this design, and will probably come in around 2.5-4 grand depending on prices when I finally purchase it.

If weight goes up significantly then I need to increase the pack size, strengthen the frame etc. It all spirals up in costs.

As Daox suggested, motorcycle brakes would work well considering the weight of the vehicle.

I wonder which would weight more, the vw bug front suspension unit, or a custom dual A-arm system? Go with the lightest.

VW suspension is light weight already and self contained, meaning you you can bolt it on with 4 bolts and have your steering and suspension all right there, otherwise something like the suspension from an ATV could work but they tend to be heavy because of the 4 wheel drive hubs and they need a frame for the shocks to mount to so they are not going to be as simple as the VW set up.
as far as brakes go, go hydraulic they are simple to work with, allow flexibility in the lines and you can use so many off the shelf parts, and as far as your regen braking goes, just have a dual stage pedal, where the first half is controlling the regen part of the speed controller and the send part of the travel hits the mechanical part.

I guess I didn't look at the picture close enough the first time (I'm not an auto mechanic by any means) and didn't scrutinize what was actually part of the suspension/steering system.

*Watches his credibility jump out the window*

=)

I have done a LOT of research on suspension design. I'm a computer engineer, not a mechanic. Quite frankly, if you need to ask about suspension, you shouldn't built it from scratch. I'm not bubble-bursting here... if you did manage to hack something together, it would probably kill you.

I don't know that I could build it from scratch even if I was capable. I only have limited access to a machine shop. I will probably just find something that seems suitable and then modify it to my needs. My main concern is that a car suspension retrofitted in will be too stiff for this application due to the low vehicle weight.

But I know that some setups can be tuned so I will have to look in to it more.

My concerns for looking into this now is that I want to ensure that I have enough space in my front compartment to attach the wheels and suspension without protruding out from the vehicle. Also need to ensure there is enough room for suspension travel.