# Weight Reduction



## Brendonbosy (Dec 13, 2007)

Some of these tips seem a little outlandish:

*Removing seats*? The passenger seat weighs maybe 25 lbs at most, unless you got power seats

*Carbon fiber*? That sh*t isn't cheap at all. If you want panelling with decent quality, you'll be looking at about $600+ per panel. CF also has many drawbacks. You often need to add backings with extra mounts and pins to support them at highway speeds. If not, you're hood will fly open into your windshield. Also, CF performs VERY poorly and dangerously in accidents. It has a tendency to shatter like glass in an accident rather than crumple.

*Magnesium wheels*? There's a reason why the UK banned these. Nevermind the extrodinary cost, mag wheels are very dangerous and highly flammable if they overheat. The most common problem is a tire blowout. They are also notoriously difficult to put out once they do catch fire.


Weight reduction is a good idea, but it has its limits when you're talking about a practical, daily driven car, not an Indy 500 or a Carrera GT supercar.


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## mattW (Sep 14, 2007)

Yeah they were supposed to go from reasonable and easy to ridiculous and expensive, i was sort of joking about the crazy stuff but i thought i would let other people decide what was reasonable... 



> Each converter will need to decide on whether or not each mod is suitable for their situation; A specialised one seater commuter will have different priorities from a family car. Some of these mods would be very expensive and/or difficult, it aims to be an inclusive list not a recommended list.


Who knows, we might get some rich environmentalist on the site who wants to build a carbon fibre specialist commuter. Who are we to say its not reasonable . You can change it if you like, that's what the wiki is for


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## JRoque (Mar 9, 2010)

Hi. This is a very old, and probably tried and true, post but I'd say you get the most bang for your buck if you change to thinner and low friction tires with the right air PSI in them. Unless you're driving a sail boat, tires will likely contribute most of your drag. A thinner tire also helps steer easier requiring less power steering assistance.

Cheers,
JR


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## Greasemonkey84 (Sep 7, 2010)

Brendonbosy said:


> *Magnesium wheels*? mag wheels are very dangerous and highly flammable if they overheat. The most common problem is a tire blowout. They are also notoriously difficult to put out once they do catch fire.


Lamborgini uses forged aluminium/magnesium alloy wheels on the murcielago SV.
The fastest Lamborgini to date.
I think if a high performance car like that can use these wheels the way they do, an elctric bug or miata won't be able to give the required performace to overtheat such wheels. Unless you go drag racing with, it instead of using it for your daily commute i don't see any reason why it would be dangerous.


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## Pirape (Feb 26, 2009)

Brendonbosy said:


> *Magnesium wheels*? There's a reason why the UK banned these. Nevermind the extrodinary cost, mag wheels are very dangerous and highly flammable if they overheat. The most common problem is a tire blowout. They are also notoriously difficult to put out once they do catch fire.


 
HUH?? I am in sales for Husqvarna global leader in outdoor products

the professional chainsaws uses a magnesium cylinder and crank case

can't get hotter than that


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## jeremyjs (Sep 22, 2010)

There's no way Mag Wheels or engine parts are pure magnesium. It's some sort of alloy that's not prone to burning. Hell half or more of an F1 car's engine including the cylinders are a magnesium alloy. Maybe if you're talking about magnesium wheels from the 50's and 60's it was true that they would burn; because they were made from pure magnesium. They were also junk. They broke easily and leaked air like a sieve.


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## ElectriCar (Jun 15, 2008)

*1940's Ford truck goal to weigh <1500lbs with batteries!*

I met a guy tonight who turned me on to some things. He has to me a lofty goal stated above. He's running the Advanced FB1-4001A with Curtis 1231 controller. Here's what he's doing or has done with the truck currently stripped to the frame. 



Cut holes in the framing where he says it won't affect the structural integrity.
Will use ALL TITANIUM bolts and nuts to put it together.
Front hubs remade from aircraft aluminum.
Aluminum Motor mount
Composite leaf springs
Carbon Fiber inner fenders
Carbon Fiber bed
Light weight brake parts, maybe ceramic rotors.
Light weight no vacuum assist master cylinder - Says it will be easy to brake too.
Delete vacuum pump due to master cylinder selection
There may be more stuff but I can't think of any now. I did turn him on to this site though so maybe he'll chime in. He's worked with race cars for years so he knows a lot of stuff because of that.


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## dtbaker (Jan 5, 2008)

*Re: 1940's Ford truck goal to weigh <1500lbs with batteries!*



ElectriCar said:


> I met a guy tonight who turned me on to some things. He has to me a lofty goal stated above. He's running the Advanced FB1-4001A with Curtis 1231 controller. Here's what he's doing or has done with the truck currently stripped to the frame.
> 
> 
> 
> ...


I am very interested in how to swap out power brake master for purely mechanical... to avoid the whole vacuum pump and switch thing would save weight, complexity, time and space under the hood!

The rest of this is sounding like the (many) 'weight weenies' in the bike racing world where grams matter when you are looking for an extra .5% of acceleration. The thing is that exotic materials drive cost up rapidly, and 'lightening' structural members is rarely a good idea. Machining cool AL parts from billet gets super expensive unless you happen to own/work in a machine shop with access to 'scrap' for free.

most of us can probably drop 50 pounds out of the car by lightening the OCCUPANTS and carrying less crap around in the vehicle.  I have made a decision to not lug around spare tire and jack in my EV; I'll never be very far from home!

I am still interested in the high 'bang for the buck' items though. For instance:
- using AL instead of steel for battery rack edges
- swapping OEM seats for light racing seats
- carbon-fiber/fiberglass hood, fenders if available
- swapping flat glass with Lexan if possible


and then doing the same for the 'major' aero mods like:
- blocking grill
- smooth belly-pan
- consider backup cameras instead of mirrors... legal?


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## ElectriCar (Jun 15, 2008)

Here's some data re weights & strength of metals.

Titanium is 1/2 the weight and strength of steel.
Aluminum is 1/3 the weight and strength of steel.

Another thing is wire weight. Aluminum is 1/4th the weight of copper and is practically the same capacity as copper but slightly less for small sizes like 2/0 it's nothing. I was running two parallel cables of 1/0 copper but recently removed the second set saving about 20 pounds. 

Because the voltage drop is so small in my truck, much less than I estimated because of wire length, I may go to #1 aluminum next week when I switch to lithium, saving even more. Because of the loss of 700 pounds in batteries, an increase in pack voltage, less sag and the much less internal resistance, my current is going to decrease a lot for a given speed. 

The smaller cables will try to warm on hill climbs but that only lasts 30 seconds at the most and wire isn't going to get HOT in 30 seconds due to being overloaded a little bit, even a lot.


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## idarusskie (Feb 17, 2011)

http://motoringjstyle.blogspot.com/2008/03/75-mpg-in-geo-metro.html

Here is one way a guy took 300lbs off his geo metro. Its not electric, but it could be.


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## TigerNut (Dec 18, 2009)

Titanium is relatively obtainable through eBay... last I checked you could buy bars of various sizes. However, it's an unforgiving material to machine and unless you take extreme care with the finishing, it can crack or corrode starting at any surface nicks (even doing line-marking with a scratch awl rather than a marker pen will leave a sufficient stress riser for a crack to start).
Making stuff out of aluminum is easier, and 7075-T6 is relatively easy to get and machines great. 6061 is even easier to get but it doesn't machine as well and it's not as strong, but it is weldable. You still need to consider the final finish and corrosion protection especially if you intend to drive your car in the winter when road crews may use salt.

Overall, replacing significant parts of your car with custom machined aluminum parts is tricky... you're replacing a purpose-engineered piece of steel that has typically already had at least one level of material minimization applied (because steel costs money), and you have to replace it with less mass of aluminum, without sacrificing streetability. Be prepared to do regular inspections of your parts to ensure you're not going to be left by the side of the road.

On the other hand, you can replace calipers, rotors, and shocks with lightweight components, sometimes at a quite reasonable premium (or even savings) compared to the OEM replacement part cost.


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## iti_uk (Oct 24, 2011)

__-_-_-__ said:


> Actually the reason why all cars are not just made with carbon fibre is because it's too expensive. that's why parts and components made with it are only seen in premium cars.


Too expensive indeed, but not due to material cost. Structural carbon fibre design is very much a black art which has been improved recently by improvements in CAE analysis techniques. This analysis is a far more deeply involved process for composites than it is for sheet metal (the reason I know this - it's my job), and the time involved and processing power required to design a small panel, let alone a whole chassis/body, drives up the development costs.

Then there is the difficulty of manufacture compared to sheet metal. Layups have to be done (for the most part) by hand and are therefore subject to operator error more than their sheet metal counterparts. Again, the time involved and the quality control required drive up manufacturing costs.

Then we must consider the end usage of such panels and parts. Delamination is a major problem with composites. When it starts it can be near impossible to detect, especially in non-sheet parts. Imagine if every sheet panel in your car was replaced by an equivalent CF part - there is no way you'd be able to detect delamination until catastrophic failure of the part. Even if you do manage to detect a fault in the part, repair isn't straightforward.

The reason why it's so popular in racing cars and RC toys (I've been a heavily involved RC enthusiast myself - yes, they are toys ) is because these are low duty applications. A CF chassis in an F1 car does not have to last more than a year's worth of limited mileage driving, and the teams are financed such that they can afford spare chassis. Their manufacturing process is very strict and precise with high rejection rates, completely at odds with the cost-efficient manufacturing requirements of mass-produced, high duty vehicles such as your daily driver.

This is all before we take into consideration the environmental impact of using CF - it is not easily recyclable.

As an analyst (and spare-time tinkerer) I don't see the use of woven composites as being "the future". High strength homogeneous sheet materials (not necessarily metals) are a far better answer to real-world requirements and efficiency/environmental objectives.

For those who like the bling of "carbon fibre" parts, there are stickers available to cover any metal part you want...

Sure, titanium is a difficult metal to work with but it has its uses. Fasteners is one very valid area for the use of titanium, sheet panels; not so much. Lightweight and strong alloys of aluminium are currently our best bet for sheet parts. There are even some high strength alloys of steel which can be made thinner and therefore lighter due to their higher strength - imagine that; lightweight steel panels!?!

Chris


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## TomA (Mar 26, 2009)

Wow, talk about getting off into the weeds...

Substitution of parts for lighter things is really only practical for heavy parts that are easily substituted. Wheels, hubs, leaf springs and brake rotors are the key components here, although for a street car without regen, aluminum brake rotors are probably not a good substitution, particularly if the car is going to be heavier than stock. It is better to go with skinnier tires and narrower wheels, but finding something that fits (alloy wheels are typically wider than steelies in the same application, not narrower) is going to be the trick.

You could go bananas and drill out all the brackets, make aluminum ones, etc. etc., but the money and time spent isn't worth the payback. Much better to take that time and money and clean up the nose and bottom of the car, eliminating cooling openings and fitting coroplast panels underneath.

Seats are surprisingly heavy. The lightest factory seats I've seen around are C5 Corvette and Toyota Yaris- both are about 35lbs. Some OEM seats are 50lbs. Fiberglass racing buckets can be 15lbs or even less with minimal padding. If you're sitting in your EV for 1/2 hour at a time, that's probably OK, and the weight savings could be very substantial.

Carpet and padding weighs a ton. Lightweight Ozite or Home Depot outdoor carpet is much lighter, and if what you have in the car is already worn out, probably worth the trouble to cut and fit.

Lastly, drilling lightening holes into anything built in the last 30 years is a bad idea. In a unibody carefully engineered for minimum weight, durability and crash performance, there just aren't any "non-structural areas" that can be eyeballed as non-essential and eliminated. Frankly, cutting the trunk panel out to put in a battery box already destroys the crashworthiness of the rear of the car. Swiss-cheesing the rest of the chassis to save a pound or two is just not a good idea, and the reason racers can do it is they have a tube steel cage in the car that more than offsets the structural losses of lightening. 

Lastly, replacing glass with plastic isn't going to be satisfactory on a street car. Maybe if you have a huge rear window hatch like the 60 pounder on a Mazda MX-3, you could consider replacing that, but all the "perspex" and "polycarbonate" racing glass I've seen, except for Speedglas, is too soft for every day use. I might use Speedglas, from Percy's, but never on a window that rolled up and down or opened (too much wear, and too hard to get an acceptable water and air seal,) and of course on a windshield you are no longer DOT compliant for road use. Also a major PITA to install water tight...

The biggest weight reduction issue most guys overlook is what they are putting into the car during a conversion. Angle iron battery racks, plates of steel and aluminum, lots of stuff that doesn't need to be that heavy. 

There's a point of diminishing return with all of this. That point is different for every application and vehicle. For racing, that point is far beyond what a road EV would cost-effectively need.

Everybody should build what they want, but that doesn't make every mod a practical exercise.


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