seafury007

[collie]

Hi
Solder the metal parts.Use Devcon [made in usa]liquid epoxy on the Ali.The devcon is drillable and can be tapped.Will take heat as I have used it to fill corosion holes in full size International Tractor engines.Have used to fix a small hole in my Mccoy60 for about 4 years.The black one seems best.Buy the primer as well.Question.If smooth flow is so good,how come all modern perpormance parts have a slightly rough[like very fine sand]finish.I tThink its called lanimer flow.If you go back to the days when Australia held the America,s Cup,the year we lost it to the USA,the american boat had very fine grooves in the hull to promote turbulance,where as Aust had a mirror finish on the hull.Those fine grooves are generally considered why your boat was faster than ours.Those boats wers state of the art.Race engine builders in Aust don,t polish ports nowdays but leave that fine sandy finish to stop the gas flow from sticking to the port walls.

[Seafury007]

Hi Collie,

Thanks for the name of a material I can use for what I want to accomplish.
My thoughts on the boat hull for you. First you are comparing air to water. Water is definately more denser than air. When a item is set on water lets say a cooking pan it will somewhat adhere to the waters surface if it is picked directly straight up. There is a friction type factor when you think of it like this. Grooves on a hull would either allow air through to break up that friction area or if they were like v's potruding downward into the water the friction area or surface to surface contact would be minimized.
In this situation you would in fact want some sort of turbulent activity there to keep the surface to surface contact at a minimum. In fact, in aeromodelling for gliders or free flight (what I fly) there has been use of turbulators along the length of wings in the forward 1,3rd of the wing section to stimulate turbulance across the wings upper airfoil section which creates better lift factors by slowing the travel time of the air across the upper surface a hair longer. Lift is created by the air moving slower across the top of the airfoil than the bottom creating and upward type pull (One theory).
As for the engine air/fuel flow situation I am talking about engines that are turning 25 to 35K rpm. You will get an extra 2k plus of rpm with a smooth flow at these high rpm's. If I was to run an engine like a McCoy 60 or K&B Greenhead 35 that is turning below 18K a semi turbulant air/fuel mix flow would probably be better due to they are single port intake into the cylinder area and you want the flow to blow out the majority of the burnt mix and fill the cylinder as much as possible.
The engines I will be modifying have anywhere from 3 to 4 ports with multi angled lines of entry into the cylinder area and thus the majority of the burnt will be blown out and so the objective is to get as much flow in and out without any delay.

Write back with your thoughts! Thanks!

[propwobble]

Robert, long time, since you lived in Washington

had to butt in here

I too have heard of a rough wing surface helping to create laminar flow by introducing an artificial lamina to which air passing over will not stick. This seems like a different idea from that of using turbolators to reattach the separation bubble which forms as a wing moves too slow or reaches a high angle of attack. As you know from adding turbulators to glider wings, the effort is intended to work on predictable circumstances at relatively constant speeds. I think Collie is referring to a slightly different method where the intent is not minimize a separation bubble but rather to decrease drag by generating a boundary layer using a very small turbulance created by a rough surface. It would seem that the only way to test the concept that Collie refers to would be to flow test various fine textures at diffent sizes and velocities. I suspect it makes little difference in a reciprocating engine due to constantly changing pressure waves bouncing around inside the crankcase never allowing anything akin to a true boundary layer to form.

I think there is plenty of turbulance for fuel atomization just from the air crossing the spraybar and moving through the ports at all angles. Polishing is of use to help stuff to not stick to the top of the piston and perhaps to smooth out any possible nicks that could become cracks on the conrod. Didn't you tell me you had a Nelson once? I say steal all the ideas you can.

Cam

[felden]

Robert
I have used JB Weld (Dark epoxy) mainly to re-profile the far end of the crankshaft port under the intake column. I do this for two reasons to make the flow contour smooth not irregular shaped, surface finish is not an issue I address, secondly it increases primary crankcase compression due to the reduction of volume. Occasionally I have used this elsewhere on crankcase internals for either or both reasons.
I clean up the metal with a Dremel first (and do other profilling) the JB Weld can be further shaped with a Dremel after hardening.

I hope that this is of use, to summarise I do this to improve airflow by changing the shape, fine surface finish is another issue.

Irvin