automotive engine boring on a mill

"Never trust anyone who asks you to."

Now you're getting nasty Dave. You're actually not the only person here who cuts metal professionally.

I watch Monster Garage from time to time. It's interesting to watch them make custom body panels. They hack away at them and then use Bondo (sp?) to cover up all the marks, dents, scratches, etc.

While this makes for a single *interesting* vehicle, I wouldn't want to make a million panels like that...

Regards,

Robin

Yeah Dave, but what do you really know about making pistons. I see, from you post, that you didn't mine the bauxite, or even collect the beer cans to melt down. You just specified the alloy. Sheesh! Cheers, Eric R Snow

jim rozen wrote in news: snipped-for-privacy@drn.newsguy.com:

Tis precisely why I prefer air gauges, and LVDT gauges, when possible.

snipped-for-privacy@aol.comNoEmails (Dave Baker) wrote in news: snipped-for-privacy@mb-m01.aol.com:

Fine, then you should already know...that it is a different location for every engine type, and even within the types, dependent on many factors (peak Kpa, peak rpm, C/R, pin offset, overall height, ring pack height, land widths, compression height, combustion chamber shape, valve sizes and placement within the cylinder, combusion gas circulation, flame propagation shape and direction, noise and emissions requirements among many others).

I have looked at your site....and...regarding making pistons... Good for you...just curious....what groove inclination did you use?

Again, nice. We produce ...ehh....somewhere in the neighborhood of 125,000 per day, just in the plant I work.

Since you got my curiosity up...I was wondering... What kind of tolerances did you hold on the profiles, and ovalites? How did you measure the profile? What shape was the ovality?...a regular, linear ovality...a double oval shape...triple oval shape...or asymmetric? ....or did you just offset the piston and do an eccentric relief (not true ovality). And what was the reasoning? Pin offset?....how much...what direction? What surface finish requirements did you have....how much oil volume was held?

Since you said you reamed the pin bore, obviously you did not use a form bore (shaped bore), nor (intentionally) an oval bore, so what did you calculate in to prevent pinboss cracking due to pin flex under load?

That I wouldn't be so sure about Dave..

Uh oh. A nerd slap-down. Who's got the biggest piston....?

This is not meant to be derogatory of course. We're all nerds here.

I'm actually not sure on this - we may be Geeks instead. I've been informed that nerds and geeks are different. Nerds for example can be female apparently. But to be a geek you have to be male.

Jim

Never trust anyone who thinks a cliche will substitute for the truth.

Look we tried and we sank a couple of test drillings but there just seemed to be a bauxite shortage in the London area. What can you do?

Nil - 90 degrees to the bore.

Well, since we were aiming for tolerances on the diameter in tenths but only had measuring equipment that read to tenths I'm sure you'll tell me we couldn't possibly determine our tolerances without measuring equipment that read, and of course was regularly certified, to read to hundedths.

How

Well we measured the i/d and added twice the skirt thickness. Oh I've already been down this route.

For prototyping I wrote a computer programme that calculated the subtended angle of intersection of a major diameter and a minor diameter for a given offset for an offset turned pseudo ellipse. Then another programme to calculate the shim thickness to offset a given major diameter by a given amount in a 3 jaw chuck. For production we always intended to sub the job out to a dedicated piston manufacturer with CNC ovality capability.

Smoothish - but then with a bit of roughness too. It was kind of tricky to specify.

how much oil volume was

Less than a handful. But then it depended on what size hands you had I suppose.

A big f*ck-off pin boss that went right up to the crown. It seemed to do the job.

Oh I think so.

I'm sure you know a lot about pistons if you work in a plant that makes pistons. Could you design and make a billet crankshaft? That was the next project. After that came Carillo style conrods from forgings and billet EN24T. We rapidly decided it wasn't cost effective compared to the dedicated manufacturers who were fully CNC tooled up for the job. A set was made for a customer's race engine though and worked very nicely. They just took too long to make.

After that came cam profile design and metallurgy and that ended up involving tappet metallurgy because the various combinations of chill cast iron, inductioned hardened iron and nitrided steel aren't all compatible with all the various tappet materials. I still do a few cams for applications that can't be bought off the shelf. My colleague still makes some semi finished blanks from EN40B bar for vintage Bentleys for another customer but that isn't part of my portfolio.

Valve metallurgy and shape for best flow was comparatively simple compared to pistons and a fair proportion of my income now comes from valves I design myself. A project that actually generated income rather than just knowledge. They are listed on the website. Valve guides were similarly straightforward and I make those on the Student from two main types of bronze depending on application and combustion chamber temperatures. Not because it's cheaper than off the shelf ones but because I can keep concentricity to nearly nil by doing it myself which means they can be changed as required without having to recut the valve seats and it enables me to maintain optimum port shapes.

The 4 butterfly DCOE style thottle bodies from billet aluminium took the longest to design and prototype. I actually made money from them until my colleague messed me about so much on the lead times I dropped them. Or we could talk about fluid mechanics and cylinder head porting. Or I could stop showing off and you could maybe admit that some people who build race engines at this level do a bit more than just throw together bits that other people manufacture without understanding how they work.

No. just a bit ticked off about comments such as "it is obvious you may not even understand what entails a quality bore"

This actually is very funny, and I'm biting my tongue...because I know who Anthony works for, and that he's very expert at the business of making high-end pistons in production, and I know who Dave is, and that he's a genuine expert at making his kind of pistons. Well, to be accurate, I know something about their companies, by reputation in Dave's case and by more than reputation in Anthony's case. I think it's likely that both of them are top-level piston-manufacturing experts, within their own frames of reference.

But they're at opposite ends of the production telescope. And it really shows.

Ed Huntress

Oh, hey, before I forget it, here's something relating to pistons for hobbyists who like to fiddle around.

When I was at Wasino and we were trying to sell Ford a $7 million transfer line for oval-turning pistons (using our then mostly-vaporware magnetostrictive oval-turning accessory), I had to make some illustrations for press releases and for a brochure. I had to show the barrel shape, and the different ovality at the top and the bottom of the piston, and the transitions.

Anyway, I was using Rhino a lot then, so we got some formulas from Ford for a very complex piston and my boss turned them into a big Excel table of data, each degree around the piston: 360 columns.

I added a column for a multiplier that I could use to multiply all of the offset values in the table. Then I started plugging in multipliers and feeding the tables of data into Rhino.

By trial and error I found values that would make the piston visibly barrel-shaped and visibly oval. I used POV-Ray to render the models so I could play with the lights, and we got some great-looking examples of what piston shapes would look like to the naked eye, if the offsets are multiplied by some very large value.

It was very tricky, because a little bit too much multiplication and you wound up with weird, distorted shapes that totally obscured the point. But there were values that showed what we wanted without turning the pistons into Klein bottles.

No, I don't have any of the images anymore. But any Rhino jock could figure out how to do it.

Ed Huntress

I don't make pistons for a living Ed. It was a one off project about 10 years ago. I design and build race engines and specialise in cylinder head flow development. It's just that over the years I've looked at most of the major components in an engine to see if myself and my colleague could make them competitively or not. Partly to make work for his CNC shop, partly so I could get exactly what I wanted without having to rely on other manufacturers, partly because the only way to really understand a component is to learn what making it entails.

Even when we decided that something was just too specialised to continue making them in small numbers without the optimum machinery it was incredibly valuable in terms of R&D, metallurgical knowledge etc and to an extent just being able to say to myself, yes I can do this if I want to now. At least now when I need something specialised I can talk to the suppliers from the POV of actually understanding the product.

Even something as simple as a valve guide means learning about the properties of an essentially infinite number of types of bronze, the ideal interference fit in the head, wear properties, coefficients of expansion etc. Get to something more involved like a piston or a camshaft profile and that complexity expands many times over. State of the art in piston design is a million miles away from what we ever achieved but at least I had the satisfaction of running an engine where I could say I actually made the pistons from scratch. They were somewhat agricultural at that stage but they worked, they didn't break and they taught me where the finer points of the design process lay.

"Ed Huntress" wrote in news:OWaud.1883$ snipped-for-privacy@fe12.lga:

Hehe... I've been finding this thread quite entertaining myself Ed. Kind of a comic relief from all the daily stress. Yes, I am quite sure we are at complete opposite ends of the spectrum.

snipped-for-privacy@aol.comNoEmails (Dave Baker) wrote in news: snipped-for-privacy@mb-m06.aol.com:

Dave, We do a lot more than pistons. And...if you would tame that huge ego for a while and pay attention, you might even learn a few things that will help you make better, more powerful engines.

Should have turned them ~10-15' toward the crown, would have made more power. (sitting on the skirt ends, grooves should go down toward the center of the piston). Also, flatness and parallelism of the flanks is of utmost importance. You see, this creates a double seal on the ring, which is enhanced by the combustion forces acting on the ring. Grooves manufactured to these specifications will seal better than gas-jet ported pistons.

I will agree on that point.

I do not understand how you can accurately measure the profile in this manner. You must measure the OD in many, many places along it's length to determine the profile. (A vertical trace is the preferred method.) And you need a guage tip radius that averages out the specified surface roughness.

So basically, it was an eccentric cut.

Pin offset is determined by many factors.

Should be easily specified by either RZ or RK and a feedrate.

Volume can be calculated from the RZ/RK + Feed + machined piston length and diameter.

Maybe you missed something here Dave. I work at a company that makes pistons, and most other engine components, yes. But I am not a 'production line worker' as you appear to think.

Could you design and make a billet crankshaft?

Yes, on both counts.

(Aside: Ed, there is that word again.)

As mentioned previously, we also make connecting rods - forged, powdered metal (cracked), and Titanium (limited-production specialty vehicles).

We also make camshafts, actuation components, valves, blocks, intake manifolds and various other engine and engine system components.

Show off all you want. Makes no difference to me. I know of what I speak, and I am quietly confident in that. I am quite familiar with race engine development, production engine development, and many other things.

BTW: - IIRC...~14 different racing championships (that I am aware of) were won using our components this year, as engineered and delivered, (no modifications after arrival at the builder), including F1, IRL, and NASCAR..... We do know a little about what we do.

snipped-for-privacy@aol.comNoEmails (Dave Baker) wrote in news: snipped-for-privacy@mb-m06.aol.com:

I stand by my statement. Your statement "Blueprinting an engine is bullshit" stands behind me on that. There is no way your hand dial bore comparator can tell you squat about your bore, except the relative diameter of the plane you measured (which may not even be square to the bore.) It tells you nothing about cylindricity, straightness, surface profile, perpendictularity to the crank and deck, offset from crank centerline or any of the mirad of other dimensions that are critical to wear, combustion sealing and power. That may have been fine 30 years ago....but it does not fly today, in either volume manufacturing....or especially, in the race world. People pay a high premium for a high performance engine. They expect quality above and beyond a production engine. From your own statements, it is apparent that your quality doesn't even approach that of a modern production engine, let alone the quality of today's true high-performance engines. And yes, I do know what kind of quality today's race engine builders are using. I find this very suprising from an engine builder of the reputation such as yours.

He's got quite the bark, but I don't see the bite...

Regards,

Robin

One can wander off to

Tom

Tom wrote in news: snipped-for-privacy@xtra.co.nz:

Tom, Check your email.

Done that. Had absolutely no verifiable content..