Mechanical Engineering

Okay. What is it exactly that you are asking a CAD to do? Are you paying someone money to perform the task of modifying the model to your specifications?

Well I was planning to do it myself, I guess costs to involve a 3rd party would be expensive? I'm willing to learn but have quickly realised that a full scan in an STP file format is not that easy to deal with, as it is one large block.

I would start by putting the step file of the existing cylinder head where we can access this file. This being the type of project, not a commercial undertaking, anyone who is willing to look at this can work on it, with the understanding, that any work is done without the expectation of any payment.

Although the step file is just a simple block, it is a place to start, the parts to be altered can cut out and the feature tree of the alterations started from this point.

Why don't you post the file already or PM it, I personally wouldn't mind taking a shot at organizing it.

ok how do I post the file here, I can't see what option to use?

You could upload to the grabcad library. If you post a link here it will be easy to find. Adding some details, type of engine it is to fit, bore, stroke, the compression ratio of existing and any other useful data you have as it will all help to come up with a possible working cylinder head

ok will do thanks

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I'll try to update with the correct tech info for it from my workshop manuals

Edwin, out of curiosity, do you actually own a 3d scanner? Was this done with an app on a phone or tablet? I ask because its an important factor.

I will find out exactly how it was scanned, as it was a friend of mine that did it - Thanks

Cost wise, this is not going to be cheap. Not only that, but the head is already design with weight savings in mind, so the existing material is thin, its also cast.

IMO you would be better off designing or having a new cylinder head designed with your idea in mind. It can be done.

That one I believe was originally a wooden sculpture(s) that was used to create the mold for the casting. A lot of talent went into creating its final shape, probable all by hand by skilled woodworkers. In England the first Grand Prix engines were produced this way.

Hi Brandon, I think you may be correct, as a resin mould was produced in order to get the casting, and I was beginning to think that it may have to be re-drawn from the start, to produce a proper 3 model in order that it could be modified.

Hi Brandon, when you talk about costs, realistically what would be your estimate for it to be re-drawn as is, then modified to an 8 valve? Is it possible to do a PM on here?

Completely new design, the head would be larger in size, weight slight more do to more valves and thicker walls for more holes in the part.

Thousands.

There are some very skilled individuals on Grabcad and elsewhere, but they will all charge you, some less, some more....and the results will vary widely. Some of their work will look like a 2 year old put play-doh between two 2x4's and some of it will look like something a NASA cad drafter would create.

You should measure the mating surfaces of the cylinder where it meets the head. Provide as many accurate measurements as possible. Design a new head based off these measurements.

Valve length, valve stem diameters, valve body diameters, sleeve diameters, gasket thickness and materials-it matters! Existing type of material, grade of aluminum used 6061, 70xx etc so we can calculate how much material to use. You need a bonified mechanical engineer for this.

This isn't scan data. If someone did scan the engine, they've gone through a lot of effort to also create a clean CAD model of the project.

This is a very complex investment casting with much secondary machining needed. Before making modifications to the number of valves, I'd make sure there is some benefit to be gained.

This is one of those projects that has no "sensible" reason behind it. It is being considered just for the fun of doing it. In the context of the possibility of making a 4 valve per cylinder head for this Norton engine,the Cad part is not that important at this stage. The first step you have already made a start on, you have had a look at the existing head casting, and in placing a well executed step file of this casting onto Grabcad you have made a valuable contribution to this site, way more than the many who come here to take but not give. This model is a good start point for making a good model of a complete Norton cylinder head assembly.

But getting back to your project. Before any Cad work is done, a possible complete valve train, from camshaft to valves has to be thought out. In the original Norton twin engine, these are opperated by push rods from a camshaft in the crankcase. With typical 4 valve per cylinder engines, the spark plug is in the center of the combustion chamber, which is roughly hemispherical, with the valves either side. The mechanically simplest method of acheiving this configuration is to use double overhead camshafts to operate the valves, a camshaft in the crankcase and push rods is probably not easily achieved, but not being familiar with Norton twins I am only assuming this.

I would be wary of anyone on GrabCad offering to work on this project for a fee, this is not a commercial project, anyone wanting to become involved is not doing this for the money but for the same reasons persons climb Mt Everest, because it is there. The best person you would want to help with possibly turning your dream project into reality would be a good practical engineer, hopefully living not too far from you, so that it is easier to collaborate with some of the skill you need.

I would not worry about the Cad part at this stage, as you start to progress to a workable concept Cad may start to become a useful tool, but just a tool, useful but not as useful as a good mill and the skill to get the most out of it. There are many pretty models here on GrabCad, that at first look impressive but when you look more closely are poor examples of engineering. You will for these types of projects need your own Cad software and skill set, eventually but most useful Cad is expensive. For this type of hobby work, take a look at this - https://www.alibre.com/atom3d/ as it is easy to learn, relatively cheap and useful

I had a crazy idea when I woke up this morning, and wondered if it might be an idea to section cut the cylinder head and re-design the valve area, then join the new section to the old, to avoid having to re-create the whole thing - just thinking out loud, and am prepared to be shot down in flames

As a starting point would anyone like to take on the task of re-creating this version, as a modifiable CAD file?

Had a quick check of the area of the valves. Looking at the 38mm dia valve a quick calculation gives us an area of 1134.1 mm 2, so to have any chance of improving the breathing for this head we need the 2 inlet and 2 exhaust valves to have more area than what is there now. Looking at your preliminary valve dimensions, for a valve 19mm dia we get 283.5 mm 2. as there would be 2 valves this dia we would end up with 567 mm 2. For a valve 25mm dia, area = 490.9 mm2 and for 2 valves this dia we would get 981.8 mm 2. If we used valves of these diameters we would end up with less valve area that what we have standard. I think it will be quite difficult to get more valve area than standard. The existing inlet and exhaust ports are quite straight and direct. This may not be worth doing as it will be difficult to make any useful improvement

ok thanks for the analysis of this area (Lawrie), it all helps me to think this project through logically, the original of course was in inches, so I've converted to mm for the sake of convenience to all others

I know there were some (limited number) 8 valve heads produced by Norton, just to test the water. I think there were 3 in total, but as to whether they were any better or not, I cannot say for sure.

If Norton played around with this idea it would be interesting to see what they did. I don't know much about cylinder head design, but the 4 valve per cylinder heads I have come across all seem to to have the spark plug in the center with the valves around the outside. I have an old Norton Manx book and the cylinder head is the same basic shape, hemisphericl, 2 large valves, and the spark plug off to one side as per the basic layout of this head. What type is the engine this head is from ?

It's a Commando 750 twin

Looking further into 8 valve Norton's I came up with this

https://www.accessnorton.com/NortonCommando/merlin-dohc-8-valve-cylinder-head-drawings.24452/

Looking into this forum that this link takes you to may provide you with more information

Hi Edwin

nice project.

I may be interested in making a CAD model for making your head.

Don not re-invent the 4 valve head, find a bike with a 4 valve head with the same bore size as your Norton.

Scan this 4 valve head and create a 3d model.

cut the 4 valve head into slices of about 5mm to show the internal geometry of the inlet and exhaust ports.

lay transparent graph paper over the sections and take a picture, I can make you an A4 grid that you can print on a transparent sheet, as used in overhead projectors.

See my City of Adelaide ship model and you will see how i created it, please note that i have discovered that this is not the best way to create a ships hull, but it is a good way to create a cylinder head.

I have found that the Suzuki GS1100 has a bore of 89.5mm and could be a candidate for copying.