Ok, I don't know much about modelling but check out the video and photos on this site, as well as a beautiful looking piece of machinery it sounds pretty nice too!

http://www.weberprecision.com/

Gareth

I am really, SERIOUSLY, impressed. That has to be one of the most incredibly complex and well made miniature engineering jobs I've ever seen.

pca

I am really, SERIOUSLY, impressed

Me too. I have only ever seen one thing that surpasses it.

See 1/3 Scale Ferrari, read the page, and watch the video (warning: it's on a slow server, takes a while to load).

Then look at the pictures here, and see the incredible detail.

This model is fully functional with a perfectly replicated mechanically fuel injected V-12 engine, 5-speed transmission, suspension, working shock absorbers, hydraulic disc brakes, accurately calibrated instrumentaion, etc. It is an exact 1/3 scale replica of the real car, right down to the number and placement of the rivets that hold the chassis together. If you could find a 1/3 scale person, he could drive the car.

Build time was 20,000 hours over 15 years (including three years to prepare the drawings). That's an average of more than 25 hours a week.

The engine is built on a larger scale than that of the V-8 that started this thread -- the V-12 is probably about 40% over-square bore to stroke (just guessing, but probably in the ballpark), the "312" designation suggests a 3.6 liter engine (12 cylinders, 300cc each) scaled down to 1/3 size, so it is a 1200 cc engine in the model. That would give a bore of about 6cm, a stroke of 3.6 cm, or 2.36" by 1.4". While the components of the V-12 are on the order of twice the size of the V-8, actual engine displacement is about 13 times greater due to greater number of cylinders and the fact that the displacement goes up proportional to the square of the bore.

I have two questions concerning the V-8 engine:

1) He made the pushrods out of drill stock, implying that they are solid steel, rather than hollow. Would this cause valve float at high RPM, or would the small scale of the engine (1" bore, .9" stroke!) make even solid pushrods so light that their weight wouldn't be a factor? They are no doubt so small in diameter that making them hollow would be impractical. [I guess the fact that he claims a 12,000 maximum RPM sort of answers my question in any case]

2) Is there provision made in the ignition system for spark advance as engine revs increase?

tanstaafl.

Yes, the ferrarri is THE most impressive engineering model I've ever seen. I saw the top gear review of it some years ago, and just couldn't stop giggling in amazement through the segment. The sheer skill involved is beyond belief.

Quote:
2) Is there provision made in the ignition system for spark advance as engine revs increase?

Yes, it's done electronically via the ignition units, which are ones designed for model aircraft spark ignition engines.

pca

As well as Top Gear, somewhere around on Discovery, or one of those sat channels, is a half hour programme on the Ferrari model.

I love these two projects
Scale Merlin
and
Corsair
The latter does not fly, but still way cool....

If you scale down a 3.6 l engine linearly to 1/3 size, would you not get about 133cc (3600/(3^3)) ?


Bonzi --

Excellent! You get your revenge for my catching your omission of the divide by two step in the 500G acceleration thread!

However, you don't get off with a total victory here. The displacement would actually be more on the order of 300 cc (I don't have time to do the math right at the moment) rather than 133 cc, because a linear reduction of dimensions by a factor of three would reduce displacement by a factor of 3^2, not 3^3.

This is because the displacement varies by the square of the bore, but varies linearly by the stroke.

Good catch, though.

tanstaafl.

The bore is three times smaller, so the displacement is nine times smaller because of that. The stroke is also three times smaller, so the displacement is another three times smaller because of that: 27 times smaller in all.

Sigh... once again my ignorance is displayed for all to see.

You are absolutely right. I actually had to sit down and plug numbers into a formula and prove to myself empirically that yes, that incredible V-12 Ferrari engine really was only eight cubic inches displacement.

On the off chance that anybody cares, here are the numbers. For simplicity, I pretended that the engine was "square", that is, bore and stroke were equal.

Disp. = Pi x 1/4 x B^2 x S (where B = Bore, S = Stroke)

3600 = .785 x B^2 x S

Since S=B, then

3600 = .785 x B^3

4585 = B^3

B = 16.61
S = 16.61

Reality Check: 3.14 x 1/4 x 16.61 x 16.61 x 16.61 = 3597 (The missing 3 CCs are from rounding errors)

So, reduce the dimensions by a factor of three, and we get

Disp. = 3.14 x 1/4 x 5.54 x 5.54 x 5.54 = 133 CCs.

Interestingly enough, given the original premise of 40% over-square design (stroke = 60% of bore), the 1/3 scale displacement still remains at 133 CC.

This makes sense when looked at from Peter's perspective that the bore being three times smaller yields a 9x reduction while the stroke being three times smaller yields an additional 3x reduction, but it was non-intuitive to me until I played with the numbers. Of course, if I had been thinking properly, I would have considered the hypothetical case of reducing the bore by a factor of three and leaving the stroke at the original dimension, and I would have seen immediately the error of my ways.

I guess the same factors would apply to the weight of the car as well. If the original car weighed, say, 2160 pounds, then the model would weigh just 80 pounds. It would be interesting to know the horsepower rating of that engine, find out if it were producing 1/27 the power of the original. That would probably put it in the 12--15 HP range.

So, Bonzi, your revenge is complete. I bow to your superior math!

tanstaafl.

We need an :eyesglazedover: smiley.