Sand Casting

[aerologic]

Hi All,

I would have asked this on my favorite CBX website, www.cbxworld.com, but it has been down for several weeks. Odd.

So over the years I have read about "sand cast" engine blocks. CBX maybe. Honda 750 for sure. I just read it about some other motorcycle engine over the weekend. For "some" Honda 750's, they had sand cast blocks. Those are hihly valued. What's the deal with sand cast engines? I know what sand casting is. I wrote software years ago to simulate the cooling of the metal in sand castings looking for porosity, voids, fatigue properties, crystal structure, etc. Why are sand castings superior? Or are they? I guess if not sand castings, injection molding is used. What's wrong with that? More precision with sand casting? I don't see how. Less machining with sand castings? I don't see how. Less flaws? I don't see how.

Somebody here will know!!

Thanks!

[shavron]

I believe it is because of the low production numbers, just my theory.

[Jess]

Before a company (in the 70's) spent HUGE $ for dies... they used to have runs made in sandcast.

Honda was not sure that the model would be successful. Before they committed a very large chunk of change to having dies made, they wanted to make sure that the model would sell. Remember in 1969, a 750 honda was unheard of... It was a BIG gamble.

It turned out to be one of the most successful motorcycles ever made. approximately 7415 sandcast CB750s were made. (according to a website that I went to) I do not claim to know if that number is accurate. True original sandcast bikes bring HUGE $... because they are rare (IMHO). Are they a better bike than the die cast bikes? Nope (again, just MHO).

People in general, place a higher value on rare. Some folks place a higher value on spending more. Look at the jillions of dollars that advertisers spend to promote brand image. Because something is rare... it must be better. Some folks want the "look at me factor", I own something rare, therefore I am special.

I have owned some very rare, (and VERY expensive cars and bikes). Were they better because they were rare/expensive... not particularly. Did they hold their value better... Hell yes.

Next time someone tells you they own a sandcast CB750, smile and say "I own an Re5... they made less"

Just my 2 cents.

Best,

Jess

[aerologic]

Thanks Jess. I had a 1977 or so CB750. Great machine. That explanation makes sense to me. I was involved in the computer simulation of casting many years ago and I can see a sand casting not being more accurate than a die casting. Plus I understand when you say the cost of sand casting is cheaper than die casting, up until some point. Good explanation!