Hello I'm about to start shopping for some materials to begin my chassis and wanted to get some opinions on weight, strength etc.

What I am thinking of doing is increasing the wall thickness of all of the 1" sq., 3/4" sq. and 3/4" od round to 14 ga instead of 16 like a book chassis.

I am using a BMW 325e as a donor. Some possibly relevant figures.
Original 325e approx 2728 lbs.
125 bhp @ 4250 rpm
177 lb/ft torque @3250 rpm
M20 engine - approx 258 lbs.

I know this engine is a little big (height mostly), but I'm not sure how it compares weight-wise to other engines. I plan on using the entire IRS system, and hope to install a 3.25 lsd as well.

Why am I thinking I may need extra strength? Call it being overly cautious. I overengineer everything I build at work. If 1/8" will do fine, I'll use 3/16" etc. I know some people have moved up to 1.25" tubing - I assume they are sticking with 16 ga. (Stalker etc.)

You engineering types - how do 1" 14 ga and 1.25" 16 ga compare to each other in strength, weight etc? I know the idea of a locost/seven is quickness through lightness, but if it will be significantly stronger/safer in a crash etc, I don't mind since I will rarely if ever take it to a track.

As usual I have rambled on -

Thanks for your responses,

Eric
Locostmonkey

Everyone in the UK is asleep right now, but when they surface again I'm sure someone will try and talk you out of using a BMW engine. There was a thread recently on just such a notion.
IIRC the concensus was the engine is too tall for a book chassis and the gearbox too wide. Weight was also an issue unless you ise one of the lighter all-alloy engines.
If you do get around the height/width dificulties, then I would question your practice of using thicker wall tube.
If you do, you're not really making matters much better; as you guessed, you'd be better off going up in tube size and retaining the original wall thickness. Have a look here.

I know the BMW looks like a good option (RWD, alloyhead etc)
but is has definate draw backs, the engine is tall and sits about a 18 degree angle in production cars, this is difficult to corrct as the oilways and oil flow system is designed for the angle. 125 bhp from 2.5l is poor.
Block is iron in the older engine meaning a lot of weight to.

If your lookiig for something of similar size. look at Alfa Romeo 2.5 V6 all alloy 160bhp off the shelf. (alfa 75) or 30l V6, same block 190 bhp. (alfa 164). these engines can be mated to a ford box if you are willing to make the effort , look at Trev Borgs page.
Or some of the Jap or Ford (eeegh) engines are almost as good (I'm bias), There are companys who design cars around the BMW system (Marlin).

Sorry if I sound negative but i did the same as you, spent ages lookig for BMW options but there was to many drawbacks, finally went for an Alfa and I'm in the middle of sorting a gearbox conversion bellhousing for a Ford box.

There is a pictur of a Viento with a BMW 6 , in Luegos web site. So it it possible.

AS for the tubing im on the "up the size keep the wall thickness the same team "
if you apply the other option and keep going you end up with solid bar which can hardly support its own weight over a long lenght

Good luck

Agree fully with above the engine is to big also the rear suspension istr on this model is semi-trailing arms which really aren't suitable, even if it has the much superior Z axle it will take a heap of inginuity to mount it and get working as it should.

theres shed loads of volvos over there !!!

live axle also

same problem with chassis - engine is tall so needs scoop or a higher chassis

using a 442 chassis will definitely help - you could fit the volvo 6 cyl - 204hp - auto gearbox tho - which can be converted to manual .

the bmw 6 is still quite a headache to fit in a 442 , ala metal hippy !

Rorty not only do you have a hottie avatar, your link has convinced me to go up in size and not wall thickness. That's just the kind of info I was looking for!

Johnmor, thanks for all of the input. I realize that my donor isn't the top of the heap, but as they say - "I'm doing what I can, with what I have, where I am"
Unfortunately I live in Kentucky in the US. Even finding anyone who could pronounce Alfa Romeo around here is unlikely - let alone a car/engine.
Since it says you're building a Viento, I'll ask - how does the Viento chassis compare to a book or McSorley +442? Are they larger? Use bigger tubing? Both?

Britishtrident - now you're the first one to make me go "oh crap" Since suspension is one of my weaker areas of understanding, I had planned on taking an awful lot of measurements from the donor and just transplant the entire IRS to my chassis by welding in brackets and braces as necessary.
Could you elaborate on why the semi-trailing arms aren't suitable, and what you think would be difficult with my approach? Is there a standard conversion process I could use?

By the way - the main reason I'm using the BMW is my donors LOW cost. I got a running donor that was in a high speed chase (complete with bullet holes!) for $152. I think that's around 90 pounds or so. I plan on using every scrap I can and only shell out cash for a few items such as wheels, tires, and front coilovers! Allthough I must say I find it funny that a single nice wheel may cost more than my donor

Thanks for all the replies - keep em coming!

Eric
Locostmonkey

quote:

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Originally posted by locostmonkey
Britishtrident - now you're the first one to make me go "oh crap" Since suspension is one of my weaker areas of understanding, I had planned on taking an awful lot of measurements from the donor and just transplant the entire IRS to my chassis by welding in brackets and braces as necessary.
Could you elaborate on why the semi-trailing arms aren't suitable, and what you think would be difficult with my approach? Is there a standard conversion process I could use?

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Teh Viento is a kit produced by Luego in the UK. It is based around using a 3.5l V8
so the chassis is about 6" wider and the wheel base is about 12" longer than stadard, but with the extra room you could just about fit any engine in.
I think they may be using a 5.7l Chevy V8

Check www.luegosportscars.com

I've done some analysis aimed at improving the strength and stiffness of the Locost chassis.

The original chassis isn't very stiff and some tubes, especially around the front, take more load as a result.

This is fine for smaller engines, remember that the "book" chassis was intended for the smaller Ford units, 1.1, 1.3 and 1.6.

Some builders have reported tubes TR1/2 bending a bit when bigger engines are used.

Try reading the Locost bits, including the bigger engines suggestions, of my results.

You can find them here-

http://locost7.info/

in the files section, title is kitcaranalysisv2.doc

quote:

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Originally posted by Johnmor
I know the BMW looks like a good option (RWD, alloyhead etc)
but is has definate draw backs, the engine is tall and sits about a 18 degree angle in production cars, this is difficult to corrct as the oilways and oil flow system is designed for the angle. 125 bhp from 2.5l is poor.
Block is iron in the older engine meaning a lot of weight to.

If your lookiig for something of similar size. look at Alfa Romeo 2.5 V6 all alloy 160bhp off the shelf. (alfa 75) or 30l V6, same block 190 bhp. (alfa 164). these engines can be mated to a ford box if you are willing to make the effort , look at Trev Borgs page.
Or some of the Jap or Ford (eeegh) engines are almost as good (I'm bias), There are companys who design cars around the BMW system (Marlin).

Sorry if I sound negative but i did the same as you, spent ages lookig for BMW options but there was to many drawbacks, finally went for an Alfa and I'm in the middle of sorting a gearbox conversion bellhousing for a Ford box.

There is a pictur of a Viento with a BMW 6 , in Luegos web site. So it it possible.

AS for the tubing im on the "up the size keep the wall thickness the same team "
if you apply the other option and keep going you end up with solid bar which can hardly support its own weight over a long lenght

Good luck

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quote:

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Originally posted by locostmonkey


By the way - the main reason I'm using the BMW is my donors LOW cost. I got a running donor that was in a high speed chase (complete with bullet holes!) for $152. I think that's around 90 pounds or so. I plan on using every scrap I can and only shell out cash for a few items such as wheels, tires, and front coilovers! Allthough I must say I find it funny that a single nice wheel may cost more than my donor

Thanks for all the replies - keep em coming!

Eric
Locostmonkey

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