Chassis: Factory build or selfbuild?

Chassis and suspension of whatever design

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Chassis: Factory build or selfbuild?

Postby Wynand on Mon Dec 05, 2011 9:31 am

Quite often in the past a newbie would be guided to rather buy a built chassis from a manufacturer rather than building one self by some forum members. Then again, quite often I made my views clear that I would rather build a chassis rather than buying it if you are capable of doing decent welds...which sort of makes me an unpopular person. That said, I based my statement on my 35 years of experience as a fully qualified boilermaker.

Here is the scenario; most if not all chassis build professionally will be welded with MIG process, more commonly known as CO2 welding and this is one of the easiest welding methods to "learn", fact. Just look at your local exhaust outlets and this will become clear.
In a factory / manufacturing engineering concerns most welders are what we call in the trade as operator welders and most of them perform MIG welding. To use a qualified welders for more commonly fabricated work would be to expensive to be competitive in the game, except where procedure welding is called for that changes the whole ball game and qualified expert (read coded) welders and expensive procedures are called upon. I run general steel manufacturing and also steel yacht building concerns for about 20 years before retiring with lots of work done for ESKOM that calls for stringent QC and procedures due to the nature of their business.
Unfortunately, a seven chassis will be classed as a general manufacturing item and be welded by a general welder (read operator) with MIG.

I always warned people that MIG in the hands of a qualified welder, things are OK, but in the wrong hands, it can be lethal. Thats the very reason I built my own chassis and intimately knows every weld, some not beautiful, but did penetrated and fused properly to the parent steel.
A qualified welder will look at a weld and know he is doing things right and if in doubt, most probably do a test piece and subject it to some destructive testing to check fusion. On the otherhand, a general welder, and again most probably an affirmative action candidate, would not go that extra mile and his/her only concern is payday - being there, done that...

And all this ramble brings me to this. I did a few years stint as a boilermaker apprentice instructor and during their welding training phase with the MIG, I would do a few welds - nice and ugly ones - on butt and fillet joints and asked them which in their views are best. To complicate things further, the nicest looking welds will be done with less penetration and will look perfect and usually are chosen by them. When I put the test pieces in a vice and with a fast tap of the hammer knock the weld clean off the steel, the look on their faces are priceless....
And herein lies my concern about "factory welded chassis by the before mentioned welders - when the frame is completely welded and stiffened up by the sum of the welds, it would be very difficult to test the welds and moreso after being shotblasted and powercoated. IOW, a chassis may be a time bomb waiting to fail.
Image
To Illustrate my point here is a picture found a seven's forum elsewhere and shows a suspension bracket weld that failed due to lack of fusion - it is worthwhile to mention it is indeed a "perfect" looking weld and done with MIG. More worrying though is the fact that this picture is of a factory built Westfield chassis... :shock:

As a parting note, please do not look upon a home-built chassis as crap, but rather ask why did he built it himself in the first place and before shooting the sheriff, inspect such a chassis before leaving negative comments. Yes, I believe there are some poorly built/welded units out there, but unfair to generalize all self-build units as suspect.
Likewise, if I have to inspect a factory chassis - especially ones build in SA and welded by affirmative action welders, I would knock a few welds off. Food for though :wink:
Personally, all the suspension brackets and wishbone welds on my chassis were welded with normal DC arc welding with E312 stainless steel electrodes for excellent strength and toughness and better penetration than MIG in these critical areas. Even TIG welding does not come close when performing a destructive test in similar suspension parts by yours truly.
Wynand
Webpage: http://5psi.net
Car: McSorley 442E chassis
2.0l Ford Pinto with ZX9 bike carbs
Lightened flywheel, camjob, 4-2-1 exh
5 Speed Ford type 9 g/box
IRS - 3.7:1 diff ratio
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Re: Chassis: Factory build or selfbuild?

Postby kalfiekind on Mon Dec 05, 2011 11:47 am

Nice!

I am no coded welder and cant do mig. My arc mostly looks like bird droppings but i never had a weld fail like that before. I work for "maak n plan engineering", meaning that when something breaks we use a lot of initiative to repair stuff. I have experienced the people you are talking about, got papars but no heart or skill, and they are easy to give up until parts arrive. They are there only for the money. Us older artisans can still maak n plan.
I believe that i have enough skill and ingenuity to do a home built chassis using arc welding, renting a mig and learning it to use it, but since I am not a coded welder I do understand that getting such a car on the road is rather difficult.
I want to build a car for road use and the occational track exercise, so being roadworthied is of cardinal importance to me.
Can a home built chassis be roadworthied and approved by sabs?
It gives extra time to kill in the Process.

Any thoughts on this provess?
Finally getting to start planning a build.
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Re: Chassis: Factory build or selfbuild?

Postby Wynand on Mon Dec 05, 2011 12:04 pm

kalfiekind wrote:I want to build a car for road use and the occational track exercise, so being roadworthied is of cardinal importance to me.
Can a home built chassis be roadworthied and approved by sabs?
It gives extra time to kill in the Process.


Yes, it can be registered - see Legal forum threads - a chap I know and haven't seen lately in Virginia got his home-built registered in 22 days. Of course there are other ways best not discussed here that is more painless and easier...
As for SABS - a manufacturer needs to supply a few chassis (not certain of how many - had a similar issue when I started to build scaffolding for certification) that will be tested ("destroyed") and evaluated for SABS approval and the manufacturer can then issue VIN numbers for registration to put it simply. My friend just through the process for the trailers he manufactures.
That said, certification does not necessary mean that all the products leaving the fabrication shop will meet the certification standards laid down by SABS, although it is suppose to religiously stick to the SABS certification specs, but some blunders may slip by :|

Enjoy your build :)
Wynand
Webpage: http://5psi.net
Car: McSorley 442E chassis
2.0l Ford Pinto with ZX9 bike carbs
Lightened flywheel, camjob, 4-2-1 exh
5 Speed Ford type 9 g/box
IRS - 3.7:1 diff ratio
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Re: Chassis: Factory build or selfbuild?

Postby muller on Mon Dec 05, 2011 12:14 pm

Wynand, you raise several very valid points. I am one of the buy rather than build advisors but you have to see it in context. Very few home builders have your expertise and experience to build a properly welded chassis. Therefore despite your reservation of the factory chassis weld quality, odds are it will be surperior to what most "regular" home builders will be able to put together.

The other considerations are time and compatibility. A lot of people under estimate the time it takes to build a proper chassis and end up abandoning their projects due to frustration. Then there is an advantage of having a factory chassis which gives you the choice of buying off the shelf parts without having to fabricate everything.

There are some stunning "home built" cars out there, but guys need to know what they are getting themselves into.
Anton

Race car 1: Birkin IRS 4AGE 20v (TLR class B - B10)
Race car 2: Birkin IRS 4AGE 20v (TLR Class B for SO - B20)
Road car: erm.. who cares
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Re: Chassis: Factory build or selfbuild?

Postby Wynand on Mon Dec 05, 2011 3:58 pm

Anton, of course you are right on several issues like for instance the time factor. Many build a chassis because he has the expertise to equal or better a factory build unit, others because of financial reasons/restrictions and to save some money and herein lies the problem. Chances are good that the person may not be well versed in welding and steel working skills if any and yes, this is usually the chassis that get abandoned giving home built's a bad name. If you cannot afford to buy a chassis, chances are you cannot afford the car and will have problems early into the build.
At the same token, some may build a chassis because he does not have immediate funds available but have time on hands and plan a long term project of lets say five years or longer and these do get completed eventually.

Personally, I did a complete scratch build and made everything - right down to a replica Lotus nose badge made from ally billet and baked enamel.. :) and originally planned to have it finished in about 6 months time. Im at thirteen months now and still building but my ride is now about 80% complete and should be burning black top middle February 2012. :oops:
Time cannot be dictated to by a self-build and always best to triple the time estimate.

Going the factory way does speed up things in a big way because parts, bits and pieces are available off the shelf so to speak but then again, individuality is not a given save for colour.
Building yourself things can be customized or adapted to ones own fancy and like in my case, have a proper GRP bootlid at the back that does wonders to the car's aesthetics, but takes time. In fact, because I built the McSorley 442E chassis (wide nose) that allows to fit my 135kg frame into, no Locost GRP body parts fitted and had to made all my own and the plugs, molds (some split molds such as nose cone) and a set of moldings took me 15 weeks alone full time to make....

But in the spirit of this thread title it is sometimes unfair to condemn home-built chassis just because of the fact it home-build since there are some very excellent examples out there.
Wynand
Webpage: http://5psi.net
Car: McSorley 442E chassis
2.0l Ford Pinto with ZX9 bike carbs
Lightened flywheel, camjob, 4-2-1 exh
5 Speed Ford type 9 g/box
IRS - 3.7:1 diff ratio
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Wynand
 
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Re: Chassis: Factory build or selfbuild?

Postby muller on Tue Dec 06, 2011 2:04 pm

Wynand wrote:But in the spirit of this thread title it is sometimes unfair to condemn home-built chassis just because of the fact it home-build since there are some very excellent examples out there.

I don't think I have ever condemmed a home-built chassis, but I always do advice extra caution before buying one.

In being fair on the home/factory build debate, some people would have seen the TLR technical bulleting regarding the rear suspension subframe failures we've seen on IRS Birkin's being raced. My car was one of those that experienced such a failure so everything is not perfect on the factory side. (No road car has experienced such a failure)
Anton

Race car 1: Birkin IRS 4AGE 20v (TLR class B - B10)
Race car 2: Birkin IRS 4AGE 20v (TLR Class B for SO - B20)
Road car: erm.. who cares
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Re: Chassis: Factory build or selfbuild?

Postby Wynand on Tue Dec 06, 2011 2:39 pm

muller wrote:
Wynand wrote:
some people would have seen the TLR technical bulleting regarding the rear suspension subframe failures we've seen on IRS Birkin's being raced.


Thats an interesting bit of information Anton. :shock:
Can you perhaps amplify on what exactly failed so we can all guard against such mishaps although we do not all own a Birkin - but this failure can perhaps shows up in the Locost and other clones .
Wynand
Webpage: http://5psi.net
Car: McSorley 442E chassis
2.0l Ford Pinto with ZX9 bike carbs
Lightened flywheel, camjob, 4-2-1 exh
5 Speed Ford type 9 g/box
IRS - 3.7:1 diff ratio
User avatar
Wynand
 
Posts: 148
Joined: Wed Aug 04, 2010 1:11 pm
Location: Welkom

Re: Chassis: Factory build or selfbuild?

Postby muller on Tue Dec 06, 2011 5:01 pm

I'll try and post some picture later, but essentially the subframe that supports the differential and front lower wishbone pickup has torn out of the chassis on 3 race cars due to to tortional force applied by the diff under hard acceleration. The bracket is properly supported in the horisontal plane, but weak in the vertical plane and this is what seems to have caused the failure.
Anton

Race car 1: Birkin IRS 4AGE 20v (TLR class B - B10)
Race car 2: Birkin IRS 4AGE 20v (TLR Class B for SO - B20)
Road car: erm.. who cares
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