neljoshua

iTrader: (2)

I know that there are numerous posts about shocks here on the forum, but I think that my question is a little different.

I have a 1983 GSL converted to electric (currently in the classified section). From the look of the responses that I have gotten, I do not think that I am going to sell it--no one is willing to pay for my time and the parts together (no suprise there).

In any event, it may be time to start some long-term planning. I would eventually like to put new shocks on the car. The after-conversion weight is a little under 2700 lbs (I think the original was 2500), so the overall weight is not a problem. The distribution, however, is different because there are about 500 lbs of batteries over the rear axle.
I know there are coil-overs and stiffer shocks, but would these be able to support this much weight? My grandfather (a mechanic) suggested air shocks so that I can adjust the height.
I do not have too much experience with shock selection--I have only installed one set. Any ideas?

Thanks
Josh

Unevolved

iTrader: (1)

I don't think airbags would be necessary, you will be able to get height adjustment with an adjustable-perch spring kit like RE-speed's. Personally, it sounds like you should be more concerned with springs than shocks, I should think a high-quality damper like a Tokico Illumina would be up to the job, if you chose your spring rates correctly.

Pele

iTrader: (28)

500 lbs of batteries are over the rear axle, but what have you removed?

Fuel !!! = 8 lbs per gallon in a 16 gallon tank, that's a quarter of your weight there.
Fuel tank - Couple pounds there.
Fuel lines, Fuel Pump, etc etc.
Exhaust system - Lotsa pounds there.


Additionally, the stock shocks and springs were rated for a few hundred pounds of cargo, which you're not carrying all the time.

Air shocks are overkill. I'd just go for a set of performance (stiffer) springs.

DivinDriver

iTrader: (15)

Um, no; the stock rated net capacity of these cars (which includes passengers and cargo) was only about 350 lbs. Varied a little model to model.

You need to get the car weighed on a scale that can determine your weight bias. Then you can figure what needs to be done with regard to springs and shocks.

Shocks are important for restraining inertia, but springs are just as important for carrying the load.

neljoshua

iTrader: (2)

Thanks for the info.

Yeah, I know that there is MUCH more weight in the back than was originally intended. Even with all the stuff I removed from the rear (spare tire, gas tank, gas, various plumbing, exhaust), I added back in a 1/8" steel box and the 6 batteries.

So...better (perhaps less "sat-in-the-junkyard-and-rusted-for-five-years") springs. Should I look at different bushings as well?

Just a question: what will happen if I get coil-overs without upgrading the shocks? I do not think my shocks are destroyed--just old.

jgrewe

iTrader: (1)

You need different springs, not shocks(well maybe shocks too, to control the stiffer spring). Pele is on the right track, you have taken at least 1/2 of the weight of the batteries in misc stuff. The stock exhaust alone is about 70 pounds IIRC. I didn't look at the car in the classifieds section but have you put any of the batteries in the engine compartment?

neljoshua

iTrader: (2)

jgrewe, yes, there are batteries in the engine compartment; four to be exact, mounted in a steel box between the two "frame" supports starting where the radiator used to be. With the electric motor and the batteries, the front end is most certainly lighter than it was originally.

What happens if you get a spring that is "too stiff"? I do not mind a little rougher ride if it means better control.

DivinDriver

iTrader: (15)

Too stiff is almost as bad for control as too soft, IMO. With suspension, you are trying to balance forces & keep things dynamically within a given range of travel and time. It's not a harmonic relationship, but it works sort of similar; It's all about damping transient forces.

That said, for a daily driver with the issues you face here (increased weight, extended moment arms) & if you don't mind having your teeth rattled, a little too stiff is probably preferable.

Urethane rear bushings for the links and sway bar would tighten things up a bit, if the original rubber ones are old. They're not load-carrying, though - - strictly control items.

Kentetsu

Using an adjustable shock, combined with a stiffer spring with an adjustable perch would probably be the way to do. Since the shock adjustment will have a significant effect on ride comfort, you won't have to be exact on the spring rate (close enough would be close enough).

I would recommend that you contact Billy (Bwaits_). His knowledge of suspension design runs very deep, and he would be very happy to advise you on a project like this I'll bet.

Good luck, it sounds like a very interesting project.

.

bwaits

iTrader: (12)

What is the background story on this. Did you do the conversion? How long ago? What does it currently handle like?

You really are not going to know what you need for spring rates until you know the weight on each end of the car.

See if you can find a set of scales. Most truck stops will be able to give you weights.

Let us know what you find out.

-billy

jgrewe

iTrader: (1)

Too stiff in the rear would cause the car to oversteer generally.

I checked out the car, pretty neat. Would it be a big deal to move two more batteries to the front over the motor? That may help out the weight distribution a lot. You might get close enough to not need new springs. The best way to find out would be to scale the car. If you don't have access to scales find a truck stop with scales and put the front wheels on the tractor pad and the rears on the trailer pad. That will get you close enough to know if you are really out of whack. If you end up with about 12-1300 at each end I would just go through the wear items (shocks, etc) and call it a day.

I've looked into doing an electric car myself, what voltage are you running the system at? I was leaning toward a tube frame Spitfire and putting a VW transaxle in the rear of it. That would eliminate a lot of weight of the seperate tranny and rear end. The guy I share a shop with has fiberglass molds for the Spitfire body and I could make a chassis.

neljoshua

iTrader: (2)

Thanks for the info. I will have to research this further.

I do not want to move two more batteries up to the front. The engine bay would be quite crammed. I would also have to get more sheet metal parts made to hold the batteries. Besides, I consider that part of the project "done." Not a bad idea, though.

bwaits, yes, I built this car myself. Not including the little bit of cleaning and repair that I did, I built it last summer from June to August (about 45 days).

Other than the loose steering (steering wheel moves about 15 degrees without moving wheels), it handles quite well--pretty close to original. Currently have one caliper that sometimes sticks (left rear). I know what I need to do to fix it and I plan to do it this weekend.

I will try to find some different scales locally. The one I used at the junkyard is just one big scale.

jgrewe, I am running 120 V (10 12 V 120 Ah batteries in series). Based on what I have seen, you should definitely go with a brushless DC or induction motor. Brushed DC motors and controllers are a little cheaper, but they can have over-heating issues, brush changes, etc. Brushless gives you the added advantage of simple-to-implement regen. Most brushless controllers have regen built in--all you need to do is hit a switch.

jgrewe

iTrader: (1)

Do a search for steering box adjustment here and you'll find its pretty easy to tighten the wheel up quite a bit.

Thanks for the motor/controller tips, I'll file that away in my grey matter for future use.

And calling a project "done", that's a good one Usually mine are called doen when I sell them, even then I end up explaining to the buyer how to do all the stuff I never got around to...

Cool project, I think an electric motor may be the only thing smoother than a rotary but I would need it to still make some brap brap sounds.

Kentetsu

Here's a good discussion on tightening up the steering system:

https://www.rx7club.com//showthread.php?t=785410

And, to use one big scale, just park front tires on the scale, get the weight, then do the rear wheels.

orion84gsl

iTrader: (5)

^ Gotta be careful with that. If the ramp up to the scale is angled then the weight will transfer to the wheels that are lower on the ramp and that will give you an incorrect reading. Using a truck stop should be easy. They don't care if your not in a truck, and it's only a few bucks. Use a CAT scale if possible. They are the most accurate, and are calibrated regularly. Most others aren't. A few times I've scaled my truck at a Flying J and after rescaling the paper told me I was a few hundred pounds heavier. Their scales do that every time.