# Has anyone biult a custome frame for an EV biuld? I am planing on biulding mine this



## PaulS (Sep 11, 2012)

Abel,
One of the biggest drawbacks to most conversions is the weight of the donor car. They are made to take not only the weight of driver and passengers but also that of the engine and drivetrain. working from the ground up consider where your torque loads will be and where your weight loads will be. You can build it lighter and therefore better performing with a longer range.
It is dificult to build a good steering system from scratch but you can use a tubular fabrication made for a car with the same track (distance between wheels of the same axle) and wheelbase (distance between the front and rear axles). Using an adjustable "coil-over" suspension is likely to be the lightest unit with the strength you need to handle "G" forces in turns and stil maintain decent tire life. (no soft tires on electrics though - it increases power consumption drastically)
Make it high enough off the ground that you can clear speed bumps in parking lots but no higher than necessary. When it comes to wiring the vehicle, have all your components and dash in place. It makes for a cleaner install.
Less over-hang on the front, rear and sides makes the vehicle handle better but if you want comfort then you have to sit in the middle between the front and rear axles.
There is a bunch more to learn but if you run into specific questions just ask.
Paul


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## Duncan (Dec 8, 2008)

Hi Abel

Have a look at locost
like these guys
http://www.locostusa.com/

I am most of the way through mine 

http://www.diyelectriccar.com/forum...-dubious-device-44370p5.html?highlight=duncan

there are a few made - different priorities for different folk


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## Abel (Sep 16, 2009)

Thank you guys for your input. Paul I have software for suspension design and that double A arm with horizontal shocks set up is the one that I seem to get perfect every time. A little bit heavier than the set up you suggested. I also have the CAD design for the spindles for my set up. Now for the fun part the frame core will be made of 3” X 6” square stock. It’s to be an I frame that is reinforced by sub frame cage. The style of the sub frame is used on aircrafts. I am thinking of bringing the two rails closer together. This will save me 15+ pounds the longer A arms will improve traction and road response. This will also allow me to use smaller motor mounts. The motor and transmission are custom made they are 12” wide and I am thinking of 16” space between the rails.
Duncan nice build what are you shooting for? Miles per charge and top speed?


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## Duncan (Dec 8, 2008)

Hi Abel
As you may have gathered I am a heretic when it comes to suspension design - I would be interested to see what you come up with

Expectations
I expect (hope) my motor will be OK to 4000rpm - and may see 5000rpm
4000rpm will be 108Kph - 135Kph at 5000rpm
Range
I looked at my driving history - I am either doing less than 25Km - or (infrequently) more than 150Km
So I have 44S 2P 16Ah cells - 4.6Kwhrs
Should be good for 30Km at 80% discharge

I expect (hope) to be able to spin the tires at up to 100Kph - If I can't then I will need more amps!


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## Abel (Sep 16, 2009)

Duncan are you using AC or DC motor or motors. If you are using DC you can use variable pulse to run your motor and it would be cooler at higher amps. Its worth looking into.


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## PaulS (Sep 11, 2012)

The part that electric car builders usually forget is that you are not running a gas engine. The torque forces are smaller and smoother than you get with the IC engines so your frame can be a lot lighter. 3" x 6" square tube is big - even for an IC car. You could be lighter and stronger using 1" x 2" square tube with a triangulated upper rail of similar size. Start thinking in ounces per foot instead of pounds.


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## Abel (Sep 16, 2009)

Paul let’s see if we are on the same page I attached to pics both from online sources. The first in the one I am talking about but different. The I shape buts the rails in-between the driver and passenger, but opens at the ends for motor placement in-between. The second pic I believe is the frame style you are talking about. Now that I am thinking of it I will draw out some scales drawing and post those.


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## Duncan (Dec 8, 2008)

Abel said:


> Duncan are you using AC or DC motor or motors. If you are using DC you can use variable pulse to run your motor and it would be cooler at higher amps. Its worth looking into.


I don't understand what you are talking about??
Please expand


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## Duncan (Dec 8, 2008)

PaulS and Abel

Those chassis are stone age - derived from horse drawn carts 
There has been a more recent invention
---- triangles ----

Seriously though a ladder chassis is OK for poodling but very inefficient if you want performance

PaulS
_The torque forces are smaller and smoother than you get with the IC engines_

Smoother I will go with - "smaller" is right out


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## mizlplix (May 1, 2011)

After a lifetime as a race mechanic/chassis tech, I would choose the car with the body style I wanted, then build a space tube frame and use the factory skin panels welded on Ala NASCAR or SCCA style. 

That way you get a very light car that looks standard but is 1/2 the weight and has a stiff compliant chassis. 

It would be easy to repair in case of damage too, just some more tubing and another skin panel.

If you were sharp, you would get a street car cheap, strip it for skin panels and parts. 

It would also have a really important thing...a title and frame tag when you went to register it. (I would have it registered, plated and put in my name before stripping it.)

I just went through this with my 1930 roadster. It was scratch built with no title. The DMV thing was a story in it's self.

Get dedicated and keep going.

Miz


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## madmike8 (Jun 16, 2011)

I'm building an electric T-Bucket. Not much to show yet... But when the time is right I will start a build thread.


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## PaulS (Sep 11, 2012)

Abel said:


> Paul let’s see if we are on the same page I attached to pics both from online sources. The first in the one I am talking about but different. The I shape buts the rails in-between the driver and passenger, but opens at the ends for motor placement in-between. The second pic I believe is the frame style you are talking about. Now that I am thinking of it I will draw out some scales drawing and post those.


Abel,
Both those frames are too heavy for an electric car. They are designed for BIG gasoline engines. 
Duncan is right - a light-weight well triangulated frame will be stronger than the "ladder" type frames that you show in your pics and lighter. You can make the area where the electric motor mounts carry the torque where it needs to go without making the entire frame heavy enough to support the weight of a 600 - 1200 pound engine and transmission. Using composits along with chrome-moly tubes you can use a pan to carry the weight of batteries that resists any damage from battery compounds - whether you use lead-acid or lithium. You cab design in cooling and /or heating as required by your batteries and the climate you operate within.
When I build my car it will use hub motors so the double "wishbone" suspension will have to carry the torque to the chassis. Hub motors are 95 - 98% efficient and although they are noisier they transmit power directly to the wheels - no transmission losses. They do present the problem of unsprung weight but I think I can deal with that with a proprietory design that I have come up with for my motors. You could accomplish the same advantage by using a transverse mounted drive motor to each of the two rear wheels. That way the weight of the motors is on the sprung chassis and you only have to deal with the weight of the jack-shafts to the wheels.
Our design critiera are probably miles apart but I am still going for efficiency just like most guys who want to make electric cars. I don't need a car to cummute with, I want one that I can drive on long road trips. That is why I am so concerned with light weight and maximum efficiency.
Paul


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## Duncan (Dec 8, 2008)

Hi Paul
Hub motors - 
There are good engineering reasons why they are as rare as hen's teeth
Unlikely to change anytime soon!


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## mizlplix (May 1, 2011)

Greetings: CRMO (Chrome moly) steels are stronger and harder than regular carbon steels, but they are not weld friendly without a lot of special pre and post heat treatment and compatible filler metals. Simply said, they are subject to thermal change induced root cracking and hydrogen embrittlement I would not pick this for a DIY chassis unless you are an expert welder and have a lot of experience with it. It is also harder to bend and in some sizes, requires special equipment.

However it is great for smaller things such as struts, brackets and plates as they are mostly bolt on items. 

Chrome moly has been used for 50 years for bicycle frames by using socket fittings and brazing. The lower temperature brazing process is sub-critical and does not cause the cracks to appear. 

Just a decent grade of regular A36 carbon steel will fill the bill nicely. It is ductile and has a decent strength to weight ratio.

The cost is lower too. 

(Sorry about the rant, a degree in metallurgy is sometimes a curse)

Miz


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## Abel (Sep 16, 2009)

Hey guy you guy have given me some good ideas. It sounds like everyone agrees that something kinda like the factory 5 frames would be best. Here are two pics the first is there GTM and the second is the MK4 car frame. Let me know what you think of this style. If any one has any pics of good frame please post them.


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## mizlplix (May 1, 2011)

They look good. When selecting an EV frame, always think battery placement....

Miz


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## toddshotrods (Feb 10, 2009)

I didn't really want to post because this subject has kind of been beat to death around here (search scratch-built) and there are more than a handful of scratch-built projects, and experienced builders, around to glean info from (almost everything in my signature is scratch-built)... The problem is that same information is simply being regurgitated, including the same misinformation that always comes up.

Miz addressed the Chrome-moly issue that people commonly think is such an easy solution, so I'll jump on one other one - ladder frames.

Ladder frames get a bad rap because of pickup trucks and old cars - modern aftermarket "ladder" style frames (actually more commonly perimeter style frames) are actually very capable. They're producing handling and autocross/road course times comparable to all the other types, except for high-end carbon racing "tubs", etc.

The advantage, for the not so well-equipped, and experienced, DIY, builder is you can build a chassis that can carry a tremendous amount of weight - safely - and with excellent results - in all aspects. You can have a really solid feeling vehicle, that can tolerate rough roads, handle well, support the weight safely, and perform predictably in a crash.

One of the main points I see here that concerns me, coming from the perspective of 30+ years of building street and race custom vehicles, is idea that simply triangulating a bunch of smaller cross-section, thin-walled, tubing will result in a safe, effective, chassis. I would suggest following a proven design or spending some time in CAD to find out where the forces are going and where triangulating will produce any beneficial results.

Another point of misinformation: the weight issue. EVs are typically as heavy or heavier than their ICE counterparts. You can't simply go lighter on the chassis because you don't have a 500-600lb engine and transmission. You still have a motor and battery pack that will, most often, weigh as much or more. That weight may be distributed more evenly throughout the chassis but it is still there and still "seen" by the entire chassis. Weight transfer under acceleration, braking, and cornering, means *the chassis has to be designed for the weight of the entire vehicle*. Most ladder frames are heavily reinforced at the points that bare the most static weight (_e.g._, the engine/front suspension area, or cargo area, in trucks), to support that weight and the forces that are transferred. The ladder frame that people like to label as being inferior, is inherently strong from front to back, requiring only adequate reinforcement in the critical areas. Torsional rigidity is not hard to obtain with them, unless you're building a ten-tenths road course car - in which case we shouldn't really be having this rather rudimentary discussion.

NOTE: I am posting this because this is a public, DIY, forum, and while the posters here may be perfectly capable of stringing together a maze of triangulated thin-walled tubing into a safe, effective, chassis - many people that will read this chassis may not be, and might build something unsafe or, at the least, unrewarding. Just think and do some research before you take that _easy_ internet advice and jump off the high-dive with it.


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## MalcolmB (Jun 10, 2008)

mizlplix said:


> CRMO (Chrome moly) steels are stronger and harder than regular carbon steels, but they are not weld friendly without a lot of special pre and post heat treatment and compatible filler metals. Simply said, they are subject to thermal change induced root cracking and hydrogen embrittlement I would not pick this for a DIY chassis unless you are an expert welder and have a lot of experience with it. It is also harder to bend and in some sizes, requires special equipment.


Hi Miz,
Just as one ex-metallurgist to another  I totally agree about CroMo not being suitable unless you have some fabrication experience and are really keen to save weight. I've played with it a little though and done a bit of reading about weldability. I found several recommendations to use mild steel filler rod, rather than a matching filler, as this reduces carbon content in the weld and susceptibility to hydrogen cracking. Even so, preheat is definitely a good idea with thicknesses of 3mm and above. Not trying to score points here – I don't have the practical experience to back this up – just wondering if you've come across similar recommendations or tried it yourself?

Malcolm


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## mizlplix (May 1, 2011)

Hi Malcom:

Yes, it is done that way in the stainless steel family too. There is a 307 filler with low end stainless properties that allows a relatively pure stainless steel piece to be attached to a mild steel hub with the strength of the parent hub (like maybe a turbine hot section).

I have even used stainless steel arc electrodes on cast iron with good results.

With T.I.G. welding the CROMO family, a mild preheat is always necessary. We usually just bury the weldment in plain sand to slow the post-welding cool time, followed by a half heat to relieve any remaining stresses that might show up after service where any vibrations are present.

Pretty standard stuff when you do it all the time, but not something a DIYer would know.

Regards, Miz


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## MalcolmB (Jun 10, 2008)

Thanks Miz. I'd like to build a custom CroMo chassis myself one day. I have a decent TIG welder that is just crying out for a challenge.


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## toddshotrods (Feb 10, 2009)

There's nothing wrong with following Miz's advice to the "T", but most race car fabricators and top notch custom shops I have seen, using 4130 Chrome-Moly don't preheat or post heat the part, or welded area, because the type of tubing generally used on a chassis is thin walled.

Here's an article on it, that seems to describe exactly what is commonly done. I still think there's more to it than just triangulating a bunch of small tubes, even if you can weld your azz of...


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## Duncan (Dec 8, 2008)

toddshotrods said:


> There's nothing wrong with following Miz's advice to the "T", but most race car fabricators and top notch custom shops I have seen, using 4130 Chrome-Moly don't preheat or post heat the part, or welded area, because the type of tubing generally used on a chassis is thin walled.http://www.weldcraft.com/2007/08/tig-welding-4130-chrome-moly-steel/.


I remember reading one of the best DIY books
Engineer to Win - Carroll Smith

He said
If your chassis builder says he does not need to post weld heat treat - RUN AWAY - FAST
And find somebody who does

Me I stick to mild steel - its a bit heavier - but then so am I


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## toddshotrods (Feb 10, 2009)

Duncan said:


> I remember reading one of the best DIY books
> Engineer to Win - Carroll Smith
> 
> He said
> ...


I usually like building in mild steel too, because it's more forgiving/easier to turn into the kinds of things I like to do. I've heard both sides of the coin, and it depends on who you're listening to. As a reference, NHRA doesn't require anything of the sort (pre/post heating), only that moly be TIG'd. If they'll put an okay on a 7.50 certification moly chassis, with no stipulation that it be pre or post heat treated, there is engineering data behind the decision - there would be too much liability otherwise. Those cars bounce off concrete retaining walls, roll, and flip, and the chassis usually always does it's job...

Again, there's nothing wrong with going all the way and pre/post heat treating - just find some data to support what you're doing. I've known some people who just grabbed an oxy-act torch and heated metal until it was glowing red and call it heat treating too. There are temperatures, rates, times, etc...


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## mizlplix (May 1, 2011)

That is a really nice article. Thanks Todd for posting it.


I knew Carrol thru my friend Bob Bondurant. He was a decent sort of chap. They both admit that during their heyday things were less scientific than they were at my time. We were about 10 years apart in ages.

On some of the old Biplanes, after the tubing was torch welded and rewarmed, we were required to drill a 1/8" hole at each end to pump linseed oil through them to anti-corrosion coat the inner surface. LOL

Times do change. Mostly for the better.

Miz


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## Duncan (Dec 8, 2008)

toddshotrods said:


> As a reference, NHRA doesn't require anything of the sort (pre/post heating), only that moly be TIG'd. If they'll put an okay on a 7.50 certification moly chassis, with no stipulation that it be pre or post heat treated, there is engineering data behind the decision - there would be too much liability otherwise. Those cars bounce off concrete retaining walls, roll, and flip, and the chassis usually always does it's job...


I have just had a motorsport approved roll cage fitted - man what a palava
They could not make their minds up about what was needed and who needed to do it!
In the end it was a specific tube and TIG welding - by an approved guy

Cost me $500 and the best part of six months - massively over-strong 

The dopy thing is the spec on the tube (it had to be that tube) was only mild steel strength

In New Zealand the requirements for use on the road are clearer and more sensible than the motorsports guys


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## Abel (Sep 16, 2009)

Hey guys you both are correct! You’re just not on the same page. Me buddy is a welder from the locale nuclear power plant. He explained to me that Como 4140 needs pre/post heat because it is more brittle. The 4130 is more forgiving. Both the 4140 and the 4130 pre/post heat is based on thickness of material. In wormer areas the ambient temperature will allow thin wall 4130 to cool down slow enough. Here is the cache the filler material my require a post heat. You will have to see manufacture’s install methods. He suggested two more thing to me for my application the first is to pre/post heat because the preheat will make is easier to tig wield it and the post heat will bring any lost strength back. The second is to make a couple of practice wields on scraps, but user similar joints that you plan to use on your builds. Wait a day look for crack if there are not any hit it with a slug hammer then check again if you find cracks try another method. A human should not be able to break cromo with a hammer. (Thor and the Hulk are excluded)


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## mizlplix (May 1, 2011)

As silly as it sounds, mild steel D.O.M. tubing is specified by many race bodies.

It has the ability to slowly deform and soak up the shock of a crash without transferring it to the driver. (crash protection-roll bars-frontal and side crush spaces)

The frames and other load bearing structures can use Chrome Moly as needed in higher stress situations where weight is a problem.


Miz


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## toddshotrods (Feb 10, 2009)

Abel said:


> Hey guys you both are correct! You’re just not on the same page...


Actually, we are pretty much on the same page. The real point is to present enough good information to guide newbies who read these threads looking for "the way" into doing more research. We're establishing basic guidelines, that warrant further research, and good planning. I cringe at the thought of people simply grabbing a bunch of materials, and following vague internet advice, to build a vehicle that will be used in real-world applications, where there are other people at risk. If you've done this for decades, you kind of develop a natural "feel" for what will work, and what will be safe, and effective. Lacking that experience, and armed with insufficient data, it's easy to be dangerous.

The real point in the Carroll Smith perspective on welding moly, and Miz's follow up on that point, is if you're not sure it's usually a good bet to over-engineer, and err on the safe side.


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## Abel (Sep 16, 2009)

Its seems that I miss under stood you two. I believe I have a pretty good idea on how to design my sub-frame and what materials to use. Now I am going to design it on CAD and run some virtual stress tests and see were some adjustment are needed. My external structure will be carbon fiber and body/crumple zones high grade fiber glass and ultra-light expanding foam. (It helps with the body shape too). I would like to thank all of you for your input and I will be posting pics of the frame and stress tests. I hope this will help others out as well and to the other DIY guys FYI am doing it this way because I have a professional wielder and a composite engineer as friends willing to help me on my build and I suggest trying to find skilled people to help you. You will be amazed how much wing, pizza and beer can get you!


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