# Weight and Drag are the key!



## Bowser330 (Jun 15, 2008)

http://www.canadiandriver.com/articles/gw/vw1litre.htm

This car gets 235mpg and is powered from a 8.5hp motor...

imagine throwing in a nice wide ranging AC setup from electro motorsport...

Any ideas on copying the over all "bullet" concept to make a commuter EV similar to this?

Tube frame with fiberglass panels...?? Lifepo battery pack?


----------



## wakinyantanka (Apr 8, 2008)

Bowser330 said:


> http://www.canadiandriver.com/articles/gw/vw1litre.htm
> 
> This car gets 235mpg and is powered from a 8.5hp motor...
> 
> ...


I've been saying this all along... That is why I have the Orion prototype, 1800 lbs total curb weight with batteries, windshield laid back similar to a Lamborghini, all aluminum suspension, all composite monocoque structure, no steel to weigh things down, belly just as aerodynamic as the top, (actually had to create a little drag underneath to keep it from becoming an airfoil.)


----------



## manic_monkey (Jun 24, 2008)

Wow! the spec of that car reads like a who's who of exotic materials. 

Getting a EV to anywhere near that weight would be a mammoth task. Even single seater formula ford race cars weight 400kg. 

take a look at http://www.dpcars.net/ for the build diary of a guy designing and building his own small sports car. I think he says it weighs in at 1000lb. so maybe 1200lb is possible with an EV?


----------



## Bowser330 (Jun 15, 2008)

wakinyantanka said:


> I've been saying this all along... That is why I have the Orion prototype, 1800 lbs total curb weight with batteries, windshield laid back similar to a Lamborghini, all aluminum suspension, all composite monocoque structure, no steel to weigh things down, belly just as aerodynamic as the top, (actually had to create a little drag underneath to keep it from becoming an airfoil.)


do you have a website to show us this prototype of yours?

1800 is pretty good, is that with AGM or leadacid?

If a 3600lbs EV can go 40-50 miles on a pack of lead acid, then....

an 1800 EV should be able to go 80-100 on the same pack.

Throw in a lithium ion pack and you are looking at 150-200....

Its all about drag and weight...


----------



## ww321q (Mar 28, 2008)

Over all I think the most important thing is , when building a performance vehicle , paying attention to every detail . I liked the idea of the mirrors "digital mirrors" . In the way of shape I think looking at the solar racer that GM made in the 80s gives a good idea of aero shape to the max . Not much to look at though . VW did a good job on that one and I think it may be worth the time to find more info on it . Efficient vehicles share a lot , weather ICE or EV J.W.


----------



## Qer (May 7, 2008)

*shudder*

I wouldn't set my foot in that thing. Don't wanna think of how it'll look after a head on collision in 40 mph.


----------



## wakinyantanka (Apr 8, 2008)

Bowser330 said:


> do you have a website to show us this prototype of yours?
> 
> 1800 is pretty good, is that with AGM or leadacid?
> 
> ...


That is with lifepo4 battery pack, no way you get that light with lead acid.
I do have a website, though it is mainly a contact page, no pictures up there until all the testing is done.
orionelectriccar.com


----------



## wakinyantanka (Apr 8, 2008)

Qer said:


> *shudder*
> 
> I wouldn't set my foot in that thing. Don't wanna think of how it'll look after a head on collision in 40 mph.


Composite construction is far safer and stronger than conventional steel construction. People don't give a second thought to climb in their cobalt or vw bug, trust me 40mph head on in one of those is not pretty, I've seen it first hand. I'll take composite over steel any day.
Lighter, stronger, faster, harder to do, thats why its not commercially available.


----------



## manic_monkey (Jun 24, 2008)

wakinyantanka said:


> Composite construction is far safer and stronger than conventional steel construction. People don't give a second thought to climb in their cobalt or vw bug, trust me 40mph head on in one of those is not pretty, I've seen it first hand. I'll take composite over steel any day.
> Lighter, stronger, faster, harder to do, thats why its not commercially available.


^what he said 

although, i do have massive reservations about the use of aluminium (not aerospace alloys) in structural roles. aluminium suffers from fatigue problems and can let go without warning


----------



## Qer (May 7, 2008)

wakinyantanka said:


> Composite construction is far safer and stronger than conventional steel construction. People don't give a second thought to climb in their cobalt or vw bug, trust me 40mph head on in one of those is not pretty, I've seen it first hand. I'll take composite over steel any day.
> Lighter, stronger, faster, harder to do, thats why its not commercially available.


I don't set my foot in a VW bug as well, trust me on that. I like my Voyager and Jeep Cherokee, according to the statistics from a Swedish insurance company that has been doing accident statistics for decades they're among the safest you can sit in in case of an accident. Probably mostly because of the raw weight of the vehicle rather than exclusive safety design...

That's a major factor in case of an accident, weight matters. A lot. A small car built in composite materials with low weight might collapse better than steel, but it won't matter much when the two vehicles movement of 40+40 mph results in a joint movement of 20 mph and you happen to sit in the vehicle suddenly going from 40 mph forward to going 20 mph backwards.

I very much prefer to sit in the vehicle going from 40 to 20 mph forward, thank you.


----------



## manic_monkey (Jun 24, 2008)

take a look at this for small car crash protection http://www.youtube.com/watch?v=ju6t-yyoU8s


----------



## Bowser330 (Jun 15, 2008)

The whole reason we are on these boards is to talk about technology, and to support people who make their own prototypes and build their own EVs.

I think its quite counter productive thinking to support gas guzzling tanks, instead you could just get a larger vehicle made from the same composite material that made the smaller vehicle..So yes it would weigh more but it wouldnt be a tank.

in the UK there are lots of small and down right tiny cars. All over the EU actually. Yes there are trucks, but usually and almost exclusively for commercial reasons, not personal reasons. Therefore with less jeep cherokees and other under-utilized tanks on the road the likelyhood of being hit by one is reduced. 

We will get there. Just wait....with current gas prices I have already witnessed in my area the number of prius's and smaller hondas or toyotas, has increased. I even see a lot more old mercedes diesels running on WVO...


----------



## wakinyantanka (Apr 8, 2008)

Qer said:


> I don't set my foot in a VW bug as well, trust me on that. I like my Voyager and Jeep Cherokee, according to the statistics from a Swedish insurance company that has been doing accident statistics for decades they're among the safest you can sit in in case of an accident. Probably mostly because of the raw weight of the vehicle rather than exclusive safety design...
> 
> That's a major factor in case of an accident, weight matters. A lot. A small car built in composite materials with low weight might collapse better than steel, but it won't matter much when the two vehicles movement of 40+40 mph results in a joint movement of 20 mph and you happen to sit in the vehicle suddenly going from 40 mph forward to going 20 mph backwards.
> 
> I very much prefer to sit in the vehicle going from 40 to 20 mph forward, thank you.


You are correct in your understanding of mass and inertia, however, the lighter, stronger composite vehicles structure would not collapse like a steel structure would. The energy would be dissipated through the entire structure, the lighter of the two objects would then be pushed out of the way and come to a stop with the passenger compartment intact. If the the fragile creatures inside are securely strapped in, they to would be safe.
Remember that the Swedish test firm has no true monocoque composite structured vehicles to run there tests on. Having seen the level of sophistication of S-2 fiberglass used on the decks of U.S. battleships to missile proof them,(yes I said missile proof), I think it will make an outstanding light weight structure. Scratch that, I know it will make an outstanding structure, I work on one every chance I get. Which is usually everyday.


----------



## Bowser330 (Jun 15, 2008)

Where can we get more information on this s-2 fiberglass?

Another thing I was thinking was making the parts out of Polyurea.

Its the same stuff that makes spray-on truck bedliners, and also what they use (believe it or not) to make buildings and walls bomb proof.

Its got incredible tensil strength and can even be applied transparently to glass/windows.

Its definately something that when used in a thin layer could be sprayed on top of foam to create strong, insulated lightweight car parts. It could even be sprayed over the entire tubeframe to cover all the welds and make the frame more robust, while prevent rust or corrosion.


----------



## wakinyantanka (Apr 8, 2008)

Bowser330 said:


> Where can we get more information on this s-2 fiberglass?
> 
> Another thing I was thinking was making the parts out of Polyurea.
> 
> ...


S-2 is aerospace grade fiberglass cloth. Just google it, you'll find what you need.


----------



## skullbearer (Jul 9, 2008)

Qer said:


> I very much prefer to sit in the vehicle going from 40 to 20 mph forward, thank you.


That is the attitude that makes it difficult to push the better safety of small vehicles.

Like motorcycles, small nimble cars not only are more cost effective but have much higher accident avoidance ability, and I'm sure studies have shown this to be the case.

Don't forget though that a lot of a a large car's 'safety' is an illusion. The modern SMART ForTwo received the same ratings and better than many huge SUV's, and yet on all the videos interviewing safety testers they complained and complained about how a small car just can't provide the safety in an accident... and finally qualified that as 'with a large SUV or truck', even while they mentioned it had better ratings than those same vehicles.

Materials all have limits, and steel frames just won't stand up as efficiently for a large vehicle because of the exponentially greater forces involved, whereas the strength of a steel frame increased by size is linear, the larger you go the worse any material performs in an accident. There is too small (and the SMART may be it, though I'd drive it any day, and after a test drive I would buy it any day too... given the money... and then convert it into an EV!!! MWAHAHAH!) and there is too big, and if you look at force vs strength calculations for accident predictions, anything bigger than a family sedan is LESS SAFE with steel frames.

Composite materials could potentially bump that size up to a small SUV or so called 'crossover', but then we're increasing the chances for accidents to happen in the first place... overall its safer to avoid the accidents through smaller nimbler vehicles and driver's training that actually TRAINS the drivers. Even the motorcycle safety course is too lax and simple, and for cars the standards in the U.S. are downright laughable.



EDIT: Back to the original subject of this thread, however... which I completely forgot I had a response to.

I myself am working with two other guys (and possibly a new member) on a hopefully sponsored Solar/EV concept vehicle. The initial prototype is to 1/2 scale and will be built on a go-kart type chassis using (initially) aluminum components for the bulk of it, or possibly a good composite. Funding will be thin so we are spending the bulk of the cash we can get on cylindrical lithium batteries, a solid vector speed controlled AC motor of 5-7kw constant, and of course the solar panels and all the outsourced specialty labor associated with a custom panel. Our hope is to do as much as we can ourselves by going through companies that make interlocking panels out of the box which are easier to wire and still nearly 30% efficiency. If anyone is interested I can post links for all the companies we get info for pricing from on another thread...

Anyhoo, the goal weight for a full size two seater who's outer dimensions will be 6x14ft is under 1400lb with two potentially 200lb passengers (so 1000lb for the vehicle). That's with a 14.4 kw vector controlled AC motor and 100miles worth of cylindrical lithium phosphate batteries, our calculations with our initial aero-designs give us a 35-60% solar power supplement at full light and 60mph, giving us a range of about (just off the top of my head here) 160-240miles... hmmm, swore it was higher but thats a top of head guestimate. Anyhoo, we can raise the vehicle weight by another 200lb of batteries and hopefully get 80% greater range, there will be space as long as its only a two-seater.

As the 1/2 scale progresses (target weight on that is under 500lb with no driver, we think we can actually do 500 with a driver) I'll make a thread and keep you guys informed as to the possibility or impossibility of our goals... so far as I can given that we have to protect our intellectual property rights on this.


----------



## Qer (May 7, 2008)

skullbearer said:


> Materials all have limits, and steel frames just won't stand up as efficiently for a large vehicle because of the exponentially greater forces involved, whereas the strength of a steel frame increased by size is linear, the larger you go the worse any material performs in an accident. There is too small (and the SMART may be it, though I'd drive it any day, and after a test drive I would buy it any day too... given the money... and then convert it into an EV!!! MWAHAHAH!) and there is too big, and if you look at force vs strength calculations for accident predictions, anything bigger than a family sedan is LESS SAFE with steel frames.


Sorry. Not buying it. There's a swedish insurance company, called Folksam, that do statistics on real life accidents and that statistics tells the simple fact that bigger cars in general are safer than smaller. It is true that within each group it varies a lot and a Mitsubishi Cosmos L300 from 88-94 is an extreme unsafe car despite it's size while a Hyundai Accent from 95-99 or a Toyota Yaris from 99-05 is extremely safe despite it's smallness, but in general the rule is the bigger the better.

A big Volvo, Voyager or Toyota Hiace, it doesn't get much safer than that and that's statistics from real life. I trust empirical data from real life more than any theoretical data. Sorry.


----------



## wakinyantanka (Apr 8, 2008)

Qer said:


> Sorry. Not buying it. There's a swedish insurance company, called Folksam, that do statistics on real life accidents and that statistics tells the simple fact that bigger cars in general are safer than smaller. It is true that within each group it varies a lot and a Mitsubishi Cosmos L300 from 88-94 is an extreme unsafe car despite it's size while a Hyundai Accent from 95-99 or a Toyota Yaris from 99-05 is extremely safe despite it's smallness, but in general the rule is the bigger the better.
> 
> A big Volvo, Voyager or Toyota Hiace, it doesn't get much safer than that and that's statistics from real life. I trust empirical data from real life more than any theoretical data. Sorry.


It's what the vehicle is made out of, and how its put together that determines it's structural integrity. That is why you see different results for different size vehicles. Spot welding as opposed to bonding can make a huge difference. 
Just my 2 cents.


----------



## Qer (May 7, 2008)

wakinyantanka said:


> It's what the vehicle is made out of, and how its put together that determines it's structural integrity. That is why you see different results for different size vehicles. Spot welding as opposed to bonding can make a huge difference.
> Just my 2 cents.


Yup, but that's only one of several factors. I watched that youtube link that Manic Monkey posted and it was interesting. Both that a Smart actually could handle the physical stress of the impact but also the conclusion that in high speeds it doesn't matter anyway since the internal organs of the passengers turns into to grounded meat due to the extreme g-forces.

If two moving objects hit each other the mass of each of them will be one of the key factors to the resulting speed of the individual objects after the collision. Now, a Smart weights 800 kilo while our Grand Voyager -95 weights 1860 kilo. Imagine them hitting eachother front to front in 50 mph. In essence for the passengers of the smart it will probably be pretty much like in that video...


----------



## wakinyantanka (Apr 8, 2008)

Qer said:


> Yup, but that's only one of several factors. I watched that youtube link that Manic Monkey posted and it was interesting. Both that a Smart actually could handle the physical stress of the impact but also the conclusion that in high speeds it doesn't matter anyway since the internal organs of the passengers turns into to grounded meat due to the extreme g-forces.
> 
> If two moving objects hit each other the mass of each of them will be one of the key factors to the resulting speed of the individual objects after the collision. Now, a Smart weights 800 kilo while our Grand Voyager -95 weights 1860 kilo. Imagine them hitting eachother front to front in 50 mph. In essence for the passengers of the smart it will probably be pretty much like in that video...


Very true. However the energy of the collision would be transfered over the entire surface area of the composite vehicle as where a steel vehicle will transfer the energy straight through. Not nearly the amount of surface area in the steel vehicle, therefore the energy of impact would definitely liquefy the organs of the passengers in any current steel framed vehicle.
Remember mass is energy, if that energy is dispersed over a larger area it is essentially "absorbed" and the passengers are effectively insulated from the impact. It would be like hitting a piece of Styrofoam with a baseball bat. Think Indy car hitting a concrete wall at 200mph and the driver walks away. (Possibly a few broken bones, but organs intact.)
Also, I'm speaking of a vehicle design that is not in mass production so keep that in mind. Composite construction is labor intensive and difficult to mass produce, steel frames, on the other hand are very easy to make. 
This is also way off topic, perhaps another thread is in order.


----------



## skullbearer (Jul 9, 2008)

My final half cent on the off-subject,

The reason many of those larger vehicles ARE safer despite theoretically and actually inferior material/construction issues, is that there is greater raw clearance (particularly front and rear) between the bumpers and the passenger areas. Given that monkeys don't ride inside the engine compartment and most people nowadays don't let the kids in the back hatch area of their fuv's, that makes those spaces massive crumple zones.

These are far larger proportionally in big vehicles than in small vehicles, given huge engines and large trunk space, and so they exceed the loss in structural safety due to the increase in size. New trucks and fuv's are designed so that the engines also are pushed underneath the car and the strong under-chassis needed to support their absurd masses.

These things plus structural collapse design specifically made for these larger vehicles has made them safer, but it still stands when you have a vehicle of comparable proportions and greater overall size, the larger vehicle does worse.

Plus they're a lot less fun to drive!


----------



## Qer (May 7, 2008)

skullbearer said:


> Plus they're a lot less fun to drive!


I disagree! I own a 4WD Jeep Cherokee and live by a gravel road. I actually think that's funnier than a BMW on Autobahn (yep, tried that too at >200 km/h). 

But I agree, this is OT so let's just all agree to disagree and sing Kumbaya together. I'll reconsider when the statistics tell a different story, until then I'll just stick with big(ger) cars. Which, of course, is both an advantage (more space for batteries) and disadvantage (more expensive convertion, more weight, probably more drag too) when it comes to converting to EV's (weak connection back to the original subject, I know).


----------



## skullbearer (Jul 9, 2008)

Qer said:


> I disagree! I own a 4WD Jeep Cherokee and live by a gravel road. I actually think that's funnier than a BMW on Autobahn (yep, tried that too at >200 km/h).
> 
> But I agree, this is OT so let's just all agree to disagree and sing Kumbaya together. I'll reconsider when the statistics tell a different story, until then I'll just stick with big(ger) cars. Which, of course, is both an advantage (more space for batteries) and disadvantage (more expensive convertion, more weight, probably more drag too) when it comes to converting to EV's (weak connection back to the original subject, I know).


I don't think doing high speed is one iota of fun. Its all about the turns baby. Highway 1 in California, grab yourself a civic or Mini Cooper or Celica and put some wear on your aftermarket sport suspension.


As for weight and drag... someone in my Calc class is trying to convince me there is a soon-to-be off the shelf 'carbon foam' which can supposedly be a near 0 mass replacement for steel crumple zones. It's either called something different or its his imagination, cause I can't find it online.


----------



## todayican (Jul 31, 2008)

A reply to the original thread: 

I am building this car! (kind of)

It uses a steel tube "backbone" style chassis 

72v D%D sepex motor 500lb of sla, and a 10hp diesel making it a parallel hybrid.

Its kind of a cross between the vw, an electrathon, and a big Bug-e

I expect it to get weigh 900 to 1000 pounds empty, go 50 under electric power, 75 under diesel power, and get 200 mpg (I hope 

pics at tshtrikes.com

let me know what you guys think?


----------



## skullbearer (Jul 9, 2008)

todayican said:


> A reply to the original thread:
> 
> I am building this car! (kind of)
> 
> ...


I think its a lofty goal. You'll need serious aero, higher pressure tires, and you'll need to run that diesal at max throttle max power with an equalling load at all times you use it to achieve that kind of mileage methinks.

Are you serious that you think you can get this to 1000lbs with steel tube frame strong enough to hold the weight of 500lb of batteries, a heavy DC motor, all the goodies to go with it, wheels, shell, and minimum safety equipment?


Can anyone spot me the average weight of a 4 banger motor, say 2.0L? Because I don't think most small cars race lightened even minus the roll-cage and motor + 550-700lb of electrical/diesal hybrid components would be 1000lb or under...

How much does the Lotus Exige weigh without the motor?


EDIT: Found the weight of the motor in the modern Exige, at this source it is listed as 115kg, which is about 253lb, the total vehicle weight of the Exige with that motor is about 2000lb, so if you were to remove the motor and add in your electronic components you are at a big whopping:

2000-253+x where x; [500,650] x being your system weight, so 2247 - 2397lb if you converted an already very light Exige.

Now lets say you had built the exige with lighter tires, no transmission (there's about 100lb in the tranny, maybe 60lb in the diff and another 15-20lb in the drive just random guestimates here) so another 180lb gone maybe for those, 20-80 for the tire reduction (rim and tread), maybe 15 in brake reduction, I'm betting no more than 400lb in frame reduction at serious strength loss potential here, you're still hundreds over 1000lb in best case.

Not to rain on your parade, are you just not planning on driving it on the road legally? Because you have to meet certain crumple/seat/belt/frame regulations to get a full roadability approval.


----------



## todayican (Jul 31, 2008)

I appreciate the input 

since its a trike (2 in front, 1 in back) its more like going up from a motorcycle, then down from a car.

however, with a box section space frame, its alltogether possible to build a 1000 pound (ICE anyway) car. there are a lot of folks building cars based on the lotus seven and beating the hell out of them on the race tracks.

I am getting the weight estimates from known numbers (like the weight of the batts etc) and the dry weight of the same style trike with only the diesel (before we decided to narrow the track width and go electric / diesel hybrid.

It is getting close to the point, like this weekend) where I can put the rolling, battery laden chassis and canopy on the scales, and I will let you know the numbers.

Thanks
Tom


----------



## ww321q (Mar 28, 2008)

skullbearer said:


> Are you serious that you think you can get this to 1000lbs with steel tube frame strong enough to hold the weight of 500lb of batteries, a heavy DC motor, all the goodies to go with it, wheels, shell, and minimum safety equipment?


I built a rack for my truck from 1"sq. tube .063 and .094 wall thickness . It weighed 60lbs and I carried over 600lbs on several occasions . I've built lot and lots of stuff from square tube . Easy to work with and very strong when properly designed ...J.W.


----------



## skullbearer (Jul 9, 2008)

ww321q said:


> I built a rack for my truck from 1"sq. tube .063 and .094 wall thickness . It weighed 60lbs and I carried over 600lbs on several occasions . I've built lot and lots of stuff from square tube . Easy to work with and very strong when properly designed ...J.W.


I guess a good point would also be that a properly constructed roll cage can essentially support the weight of the vehicle and more, and yet a solid cage usually only adds... what? 50-100lbs? I don't know, haven't handled an entire roll cage outside a car before.

I guess you could build a good strong frame with high grade steel tubing on 300lbs maybe? I'm talking 2 or tight 4 seater with some luggage.


----------



## wakinyantanka (Apr 8, 2008)

skullbearer said:


> I guess a good point would also be that a properly constructed roll cage can essentially support the weight of the vehicle and more, and yet a solid cage usually only adds... what? 50-100lbs? I don't know, haven't handled an entire roll cage outside a car before.
> 
> I guess you could build a good strong frame with high grade steel tubing on 300lbs maybe? I'm talking 2 or tight 4 seater with some luggage.


Any ground up build would be wise to consider the advantages of composites. Check out this article:http://www.techlink.net.au/lambo/murcielago.pdf
This is how I'm doing my build, Although I'm not going topless.


----------



## Technologic (Jul 20, 2008)

wakinyantanka said:


> Any ground up build would be wise to consider the advantages of composites. Check out this article:http://www.techlink.net.au/lambo/murcielago.pdf
> This is how I'm doing my build, Although I'm not going topless.


If you're going ground up with composites (fiberglass is ungodly cheap these days) you should use aluminum... remember that hardness is exponential not to weight but to thickness... and since aluminum is roughly 50% as strong as high grade steel yet around 3 times lighter per kg you will acheive about a 9 times increase in strength.


----------



## wakinyantanka (Apr 8, 2008)

Technologic said:


> If you're going ground up with composites (fiberglass is ungodly cheap these days) you should use aluminum... remember that hardness is exponential not to weight but to thickness... and since aluminum is roughly 50% as strong as high grade steel yet around 3 times lighter per kg you will acheive about a 9 times increase in strength.


This is true, however a foam core composite will weigh three times less than aluminum and have eleven times its strength. Also, aluminum behaves like plastic when its stressed,i.e. a crash, so from a safety stand point the composite is also superior. That being said composites are extremely labor intensive, so aluminum has the advantage there. I guess it would be a trade off, probably why Tesla went with a bonded aluminum frame and carbon fiber panels on the outside.


----------



## CNCRouterman (May 5, 2008)

Ok, if memory serves me correctly, Strength, not hardness goes up with the cube of the (section) thickness. However, composite's superior strength is in tension, not compression, correct?
It is my understanding that composites tend to have *relatively *poor properties with respect to buckling and compression strengths, therefore to design a structure to perform a controlled collapse, you have to provide for different forms of collapse than you would with metal. You would want to change the energy absorption path from columnar to tensile, like pushing a rope, futile unless you put the rope in a tube. Of course, having a big ole chunk of styrene or polypropylene or polyethylene foam of modest shore value will provide a good deal of energy absorption too.

As far as aluminum goes, fatigue strength properties vary with the alloy, as do corrosion resistance and strength (ultimate). Also, fatigue properties depend on load, so if you design to stay below the fatigue threshold, fatigue become almost a non issue.

I don't understand the reference to aluminum acting like plastic under stress. If the reference is to it's malleability, that is not necessarily a bad thing, plastic deformation takes energy, and would be preferred to rupture, where there is no more energy absorbed once failure occurs.


----------



## todayican (Jul 31, 2008)

Ok I dont know if its good manners or not, but good service is so friken rare these days I will do it anyway, I just called Erik (CNCRouterMan) to talk about having his company cut the mold for my trike out of foam or mdf, and he went through the options patiently, and thoughtfully. I was thouroughly impressed (and the "ballpark" figures he was quoting for the job were more then fair.

Erik, Thanks.

If someone is interested in CNC routing, I would seriously consider giving him a call...

Tom


----------



## Technologic (Jul 20, 2008)

CNCRouterman said:


> Ok, if memory serves me correctly, Strength, not hardness goes up with the cube of the (section) thickness. However, composite's superior strength is in tension, not compression, correct?
> It is my understanding that composites tend to have *relatively *poor properties with respect to buckling and compression strengths, therefore to design a structure to perform a controlled collapse, you have to provide for different forms of collapse than you would with metal. You would want to change the energy absorption path from columnar to tensile, like pushing a rope, futile unless you put the rope in a tube. Of course, having a big ole chunk of styrene or polypropylene or polyethylene foam of modest shore value will provide a good deal of energy absorption too.
> 
> As far as aluminum goes, fatigue strength properties vary with the alloy, as do corrosion resistance and strength (ultimate). Also, fatigue properties depend on load, so if you design to stay below the fatigue threshold, fatigue become almost a non issue.
> ...


shattering as in ceramics or resins absorbs more strength than plastic metallic deformations.... so ideally if you could hot cast AlO or carbon into ceramics that would be best for weight and crash safety  You'd also want solid tungsten molds so it doesn't melt at 2500C 

ideally for a body panel price wise you could injection mold akulon plastic with hollow glass spheres suspended in it... this would be super light yet stronger than carbon fiber per lb.

Just FYI.


----------



## aeroscott (Jan 5, 2008)

Technologic said:


> shattering as in ceramics or resins absorbs more strength than plastic metallic deformations.... so ideally if you could hot cast AlO or carbon into ceramics that would be best for weight and crash safety  You'd also want solid tungsten molds so it doesn't melt at 2500C
> 
> ideally for a body panel price wise you could injection mold akulon plastic with hollow glass spheres suspended in it... this would be super light yet stronger than carbon fiber per lb.
> 
> Just FYI.


I've used epoxy /hollow glass spheres . what is akulon ? I'm thinking a thermoplastic but stronger then carbon . Ive heard about putting nanoparticles in the epoxy/ carbon to add compressive strength . thermoplastics have much better delamination strength .


----------



## Technologic (Jul 20, 2008)

aeroscott said:


> I've used epoxy /hollow glass spheres . what is akulon ? I'm thinking a thermoplastic but stronger then carbon . Ive heard about putting nanoparticles in the epoxy/ carbon to add compressive strength . thermoplastics have much better delamination strength .


They make different kinds of the elastomer akulon from DSM engineering (best plastics company in the world at the moment).

http://www.dsm.com/en_US/html/dep/akulon.htm

There are high compression versions that top out in the 300GPA modulus range. it weighs about 2.5 g/cc (less than aluminum) as well. Glass spheres provide massive compression stiffness per gram (as all hollow spheres of ceramics do). 3M makes them.


----------

