46 replies to this topic

[Cooperman]

Have to say that if I was going to build a hybrid I wouldn't use a classic Mini as the basis because of the engineering limitations and thus the high cost.

It would be easier and far cheaper to build, say, an MGB with a small-block American V8 or even an MG Midget with the A-series replaced by a Mazda MX5 unit. To replace with a normally mounted but more powerful engine in a conventional front engine rear drive car is usually quite simple. In fact, the MGB was produced as a V8 by MG using the small-block Buick V8.

The Ford Escort & Cortina are good for different engines and the Cortina has been fitted with many different engines, often Ford units like the V6 Granada unit.

Doing that sort of engine change does not create the same structural implications or safety issues either.

The problem with the Mini is the cost of making a complete new sub-frame and drive shafts, plus a potential lot of body welding to get everything in. The packaging design of the classic Mini was a masterpiece, especially when it was done back in 1958 - 9. In fact, that is what makes the Mini such a design classic in its own right. Issigonis was a genius.

I have a 1971 MGB-GT sitting outside my workshop. It's my Grandson's and we have considered fitting a Buick V8, but we have decided to stick with the B-series in order to maintain the value of such a classic.

[The Matt]

The space limitation of the Mini engine bay puts me ofc the idea now. Flip front vs retaining the inner wings is the driver for the engine conversion in my mind.

if you're willing to hack the inner wings off then there are plenty of conversion options. There's obviously a whole load of pros and cons that I won't go into there.

A mate of mine has recently done a Ford Focus ST170 engine into an MGB. Looks like an excellent conversion!

[Cooperman]

A friend of mine has a 1.8 Honda V-Tec engine in a Mini and, quite frankly, it is cleverly engineered, but cost an absolute fortune. I test drove it and although it is quick in a straight line, I did feel that the change to the basic body structure was causing some strength issues and it did feel poor in hard cornering. Maybe it was just this car, as I have driven others with different engines and they did not feel unsafe as this one did, just didn't feel like a classic Mini to me.

With a hybrid Mini it is the structural issue as well as the drive line and lack of space which makes it both difficult & expensive.

The Mini is a monocoque structure and without a lot of stress analysis it is impossible to determine whether the modified structure is 'crash-worthy', or even fatigue capable.

I used to be in aerospace design and I'm very sceptical of the so-called flip front designs. Who has done he finite element analysis of the bracing bars which replace a large part of the load-carrying structure? Probably no-one and it's just a guess.

[DomCr250]

I think we all agree that different aspects attract different people to mini ownership.

 

Conversion costs are down to your own ability, if you need to pay people to make subframes, driveshafts and looms then it will cost more.  That is why I suggested the K series on a metro frame ... it's basically a parts bin type swap with some electrical work.

[JOE123]

im thinking of making up a few designs

[The Matt]

I used to be in aerospace design and I'm very sceptical of the so-called flip front designs. Who has done he finite element analysis of the bracing bars which replace a large part of the load-carrying structure? Probably no-one and it's just a guess.

An ex-colleague of mine designed a composite sprint shell many years ago. He did a very detailed FEA of the whole vehicle. Flip front vs fixed with inner wings, steel vs composite. Reading his results was very interesting and the flip fronted composite shell that came out of the design was torsionally stiffer and turned out lighter than a steel counterpart too.

It wasn't designed for road use, purely for sprint use. But the data is 95% there if he were ever to analyse it all again.

[JOE123]

 

I used to be in aerospace design and I'm very sceptical of the so-called flip front designs. Who has done he finite element analysis of the bracing bars which replace a large part of the load-carrying structure? Probably no-one and it's just a guess.

An ex-colleague of mine designed a composite sprint shell many years ago. He did a very detailed FEA of the whole vehicle. Flip front vs fixed with inner wings, steel vs composite. Reading his results was very interesting and the flip fronted composite shell that came out of the design was torsionally stiffer and turned out lighter than a steel counterpart too.

It wasn't designed for road use, purely for sprint use. But the data is 95% there if he were ever to analyse it all again.

 

******* getting technical now lol and ive just designed part of my project lol

[The Matt]

Yeah. You don't want to get technical when you're designing stuff.

[JOE123]

im not its u lot getting technical lol

[Cooperman]

How else can you re-design an existing product to accept a completely different power unit from the original without 'getting technical'. It's a technical issue..

For example, to change the engine in an aircraft requires a 'major modification' application to the Civil Aviation Authority (now EASA). The application must contain full engineering drawings and a detailed stress analysis signed off by a qualified person.

With a car it seems as though some people think they can just 'guess' at what will meet the static, dynamic and fatigue stresses and still be safe to drive.

To any qualified engineer that is clearly nonsense.

The worry is that one of these badly thrown together modified cars will crash, taking out a bus queue, and that will lead to any and all modifications, even a minor alteration such as slightly stiffer dampers or higher rate springs, being banned completely.

How to bring Mini-owning into disrepute!

[The Matt]

My sentiments exactly. "Design" is a term banded around far too much.

[Cooperman]

In my business which was engineering design consultancy (retired now, thank goodness) we once received a contract from Austin-Rover to move the engine in the Princess 2200 a distance of 27 mm further forward. This was because the drive shaft angles were not acceptable and were causing a lot of failures.

Now just to do this job required hours & hours of design plus calculations in respect of the strength of the mountings and tie-bars using proper design and analysis tools.

How can it be certain that fitting a completely different engine into a car will be adequately done if the persons doing it have no design  or stress analysis experience.

Of course, the big problem, even if the skills are there, is obtaining the initial strength figures unless strain gauges are fitted and re-analysis of the original structure is carried out.

Design includes stress analysis with due consideration to fatigue life and reserve factors for crash cases.

It is very complicated if done correctly.

[Captain Mainwaring]

How else can you re-design an existing product to accept a completely different power unit from the original without 'getting technical'. It's a technical issue..

For example, to change the engine in an aircraft requires a 'major modification' application to the Civil Aviation Authority (now EASA). The application must contain full engineering drawings and a detailed stress analysis signed off by a qualified person.

With a car it seems as though some people think they can just 'guess' at what will meet the static, dynamic and fatigue stresses and still be safe to drive.

To any qualified engineer that is clearly nonsense.

The worry is that one of these badly thrown together modified cars will crash, taking out a bus queue, and that will lead to any and all modifications, even a minor alteration such as slightly stiffer dampers or higher rate springs, being banned completely.

How to bring Mini-owning into disrepute!

 

 

Look at some of the junk thrown together and you'll see that engineering doesn't come into it. It makes me weep to read threads about braking system "conversions" when not one calculation has gone into the seeing what will happen when you mess around with things - sometimes the complete naivety terrifies me.

Regarding conversion - of course the easy way is just to over engineer everything, but that still doesn't allow any room for fatigue issues, it's not just all about out and out strength.

[Cooperman]

Quite right there. The engineering expression 'fit, form & function' comes to mind. Not too heavy as that increases the inertia and braking requirements, not too weak or it will fail, not too expensive to make or it will be non-viable.

One job my company did was to put together the engineering team which put the engine and transmission into the Ford Group 'B' RS200. That was a design team of 5 people who took almost 3 months to do the complete design & analysis.

The Honda-engined car I tested did feel most uncomfortable when cornering hard. It felt as though the front end was 'winding up' due to lack of torsional rigidity, which was probably the case. It was a clever installation, but I did doubt its structural integrity. Just put together by mechanics with no formal engineering design qualifications one might guess.

[Captain Mainwaring]

It's a lot more complicated than it looks

 

I've seen some photos of home built subframes and feel somewhat terrified when I look at some of the design concepts. 

Just as well no one flies in them.