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

[Blue Bomber Man]

So some good news. I decided to estimate the frontal area today based on my current design. It looks to be just under 1 m^2 (~9.5'). I am hoping to get the Cd under .2 which will significantly be better then the estimates I had when I was thinking of doing a motorcycle instead of this. This is important because I think that I will be over my weight estimate of 350 lbs instead coming in around 500ish or higher.

This large difference in weight will be more then offset by the improved aerodynamic drag and will make the battery requirements a tad easier (as well as making top speed and range easier to achieve).

[Coyote X]

Some considerations to look at are strength, weight, and reliability. Using an ATV suspension will give you a light weight setup that is not that strong or reliable. Having driven/owned ATVs for years I can tell you they hold up to 5-10,000 miles of use and are pretty much done for. The ball joints and other pivot points are just not made to last that long. The brakes on them are usually undersized to start with and they make up for it by going to softer pads. So typical easy use you get at most 1500 miles on a set of brakes. The cable operated brake systems on some of the older ones are junk and would be really dangerous on the road. Hydraulic brakes are much easier to maintain and use.

Motorcycle brakes are usually bigger and will last longer. You could probably get 5-10,000 miles on a set of pads as long as the total weight was around 750lbs. Motorcycles will have a lot better suspension reliability so it might be possible to use them.

If you want a setup that is light weight(for a car) and reliable the main choices seem to be a VW beam front end or a Mustang II. Both of them are pretty light weight. Places like Jegs and Summit sell complete Mustang II front suspensions that use light weight parts if you can't find one at a junkyard. Any custom made parts will also wear out over time so you will have to make new ones as the old ones wear. So using existing parts as much as possible saves a huge amount of trouble later on.

I guess a lot of it comes down to what you ultimately want the car to do. If it is going to be driven for 20 years and last 200,000 miles it needs a totally different design than one that is just driven occasionally and mainly just to see what you can push the limits to. Designing for long life means it will end up looking and acting much more like a standard car and end up being heavier than you want. It is far easier to find existing car parts that do what you want and adapt them onto your frame than try and make anything and have it reliable.

My first car I built was using lots of custom parts and parts of a dozen different cars. It is nearly impossible to work on it without using a welder to just make something else fit since I can never find replacement parts or even half the time remember what car the part came off of to get a new one.

My second car was much better, it stayed 100% Metro parts at the expense of making it heavier and less flexible in overall design. But I can pretty much go anywhere and get parts to fix it. That makes a huge difference if you plan on driving it daily.

[Blue Bomber Man]

I am definitely hoping to get long life from this vehicle and that's an excellent point about custom fabed parts versus existing components. I am almost certain that the finished weight of the vehicle will come up 750 pounds and additionally I hope that 75% of the braking will come from the regenerative forces which should further help maintain the lift of the front brakes.

I will look into those two suspensions and see what sort of adjustability they have and how much they weigh. If it seems like a viable solution I will have to get more specific measurements on them and decide whether I should modify the chassis slightly or modify the suspension so it fits. All depends on what is more feasible of course.

Thanks for the help!

[MazdaMatt]

regarding your concern about stiffness of an OEM suspension... you can always replace the springs. But really, you're working with 3-wheels, so you get 25% more weight on each wheel than a 4-wheel version, and you'll be lugging around batteries. Besides, stiff = fun

[Ryland]

The front end of a VW beetle is pretty light, total car weight is around 1,400 pounds with a good deal of that being in the rear where the engine is.
my electric car is 1,400 pounds with 500 of that being batteries leaving 900 pounds for body, frame, drive train, seats, doors, windows, if you think you can make a safe vehicle that weighs much less then that then it is either going to cost a great deal or you have alot more experience doing this then you appear to.

[Blue Bomber Man]

This will vehicle will weigh between 500-750 pounds with batteries (the battery pack is around 100 pounds for 5kw-hour pack)

No, it won't be nearly as safe as a normal car, it will be safer then a motorcycle though. For those of you curious as to how it will be so light, check out the blog it has links to TREV and their construction methods.

I may add some sort of side impact protection, but we'll have to see.

[Blue Bomber Man]

Small update: Posted a few more photos on my blog this evening. Getting a little burnt out from working on it so I probably won't have anything new till Saturday.

BenW’s blog - Vox

On a side note if anyone wants access to the .sldprt or .sldasm files for this project let me know.

[Blue Bomber Man]

It has been a few days since I've posted anything so here's some updates:

I've been learning a lot about how to build things in SolidWorks and I've decided to rebuild the chassis from scratch for increased accuracy and customization. There is a lot in the program about setting relationships instead of dimensions. This allows you to change one part and Solidworks will automatically adjust other dimensions as needed to match the relationship requirements.

I have been exchanging emails with one of the guys that headed up the team that developed the Trev from Australia. He has given me some insight on problems that came up with the final design of the Trev. The main concern he brought to me is thermal expansion of the canopy. The acrylic they had blow molded expands significantly with varying temperatures and means that that the carbon fiber lining which reinforces the canopy forces it deform, making a seal impossible.

That unfortunately is a pretty big setback and I am looking for ideas to get around it. I'm hoping someone has some experience with custom windshields that have some ideas. I'm currently thinking of something like a 4 piece canopy, 3 of safety glass, one (the top) of lexan.

Hopefully tomorrow I will have some new screen shots up, but unfortunately they will probably not show much of anything knew. I am going to look into making the renders look better though for presentation purposes.

[Blue Bomber Man]

New update on the blog. Latest screenshot is of the entire car. This update has improvements to the front wheel well to give greater wheel turning movement.

On a side note, I need help figuring out how to post SS's directly in my post. I've tried the option before but it just give's a link to my blog's pic without a thumbnail or a full picture. Do I need to upload the photo somehow directly to this website?

Thanks for the help!

[Blue Bomber Man]

New photo's on the blog: Ben's Custom EV Blog

Please check it out and comment.

Latest update includes sidewells, thoughts on new ideas, and of course photos!

The total mass of the that setup so far is 150 pounds. That includes:
Chassis, Tires and Wheels, seat.

That leaves around 300 pounds for batteries, controllers, suspension/steering and a motor. Also needed: Canopy, body (actually that part is VERY light, you will see), misc stuff: lights, ventilation/motor cooling, comm station