Jump to content
Sign in to follow this  

Glass beading engine cases

Recommended Posts

Hi all, I hope I can get some good feedback posting this here.

I'm doing a bottom end rebuild and want to use the glass bead blaster we have at work. The beads are very fine grit.

Will this effect the sealing surfaces?

What's the best way to clean the cases after glass beading ?

Should I clear coat the cases after?

I'm looking to hear from people who have done this before.

Thank you

Share this post


Link to post
Share on other sites

I assume you're removing / replacing all bearings? Soda blasting would be better because it dissolves when washed. Stay away from any sealing surfaces. Clean real well with hot soapy water then rinse with hot water. Tape off all sealing surfaces and clear coat with engine enamel.

Share this post


Link to post
Share on other sites

Using a glass bead blaster, you can bore a hole straight through an aluminum engine case.  But you should also be able to avoid that.  Frankly, I would rather not use glass for anything that has an oil passage in it because of the risk of contamination.  Soda is much more suitable, but I'd just rather not.  Every bearing and seal will need to be removed.

Share this post


Link to post
Share on other sites

I was planning on leaving every bearing and seal in place when I blast the cases. Then I will remove them clean the cases and install all new bearings and seals. I heard electrical tape works great to mask the sealing surfaces.

I also heard glass cleans up easily with water and soap ?

Share this post


Link to post
Share on other sites

I also heard glass cleans up easily with water and soap ?

 

The beads on the outside surfaces are easy enough, it's the risk of glass becoming lodged in the interior of oil passageways that would keep me from using it.  You could conceivably run water through a passageway and fail to remove one or more beads.  Not so with soda, as it will dissolve even if it is stuck in place. 

Share this post


Link to post
Share on other sites

The beads on the outside surfaces are easy enough, it's the risk of glass becoming lodged in the interior of oil passageways that would keep me from using it. You could conceivably run water through a passageway and fail to remove one or more beads. Not so with soda, as it will dissolve even if it is stuck in place.

The cases are for a 2 stroke, the only oil passages that would be exposed are to the main bearings but I could fit a plug in there as well as a q tip or small brush to clean after.

I can't put soda in the blasting can at work so if I used soda is need to get or make a media blaster

I just love how the glass bead finish looks

Share this post


Link to post
Share on other sites

The cases are for a 2 stroke, the only oil passages that would be exposed are to the main bearings but I could fit a plug in there as well as a q tip or small brush to clean after.

I can't put soda in the blasting can at work so if I used soda is need to get or make a media blaster

I just love how the glass bead finish looks

 

the glass embeds itself in knooks and krannies.

Share this post


Link to post
Share on other sites

Its tedious and risky and yes it will ruin the.gasket surfaces. Beads are hard to keep out of the bearings with them being blown everywhere...even with tape...but its not completely impossible. Just like space flight.

Share this post


Link to post
Share on other sites

If all you're trying to do is get the cases clean and pretty, just hot-tank them. They'll come out looking like new, and none of the issues from bead blasting will apply.

Share this post


Link to post
Share on other sites

If all you're trying to do is get the cases clean and pretty, just hot-tank them. They'll come out looking like new, and none of the issues from bead blasting will apply.

What is a hot tank ?

Share this post


Link to post
Share on other sites

It's a tank full of heated and agitated detergents to clean engine blocks, parts, radiators, etc. Some shops also have ultra-sonic set-ups that add to the cleaning power.

 

Make sure the place you go to is using a cleaning formulation that is safe for aluminum. The traditional lye solutions would dissolve aluminum, although there aren't many places using these any more due to increasingly strict hazardous materials regulations.

Share this post


Link to post
Share on other sites

 I would not do it at all, To me it is not necessary.  Ask yourself, how will this improve engine performance?  If you do not have a clear answer then do not do it.   What does help is taking center cases to a LAPIDARY shop (this machine is found in ROCK polishing shops) and flattening the mating surfaces of the center cases so they match tight.  Only take off .001-.002 thousands of an inch, or  you have to re shim. 

Share this post


Link to post
Share on other sites

 What does help is taking center cases to a LAPIDARY shop (this machine is found in ROCK polishing shops) and flattening the mating surfaces of the center cases so they match tight.  Only take off .001-.002 thousands of an inch, or  you have to re shim. 

 

NEVER do this.  The center case joint has to be precisely square with the crank and other shaft axes, and there is no way to accomplish that with a rock polisher.

  • Like 1

Share this post


Link to post
Share on other sites

NEVER do this.  The center case joint has to be precisely square with the crank and other shaft axes, and there is no way to accomplish that with a rock polisher.

 

 

Oh yes.  Only 1 or 2 thousands exceeds most of the manufacturing tolerances of the cases.  That is why most companies do not run a center gasket.  It makes maintaining tolerances easier.  That is why engine cases use dowels for alignment.  The dimensions are CRITICAL and you don't need to do anything that might change them.  One or two thousandths may not seem like much to you but in a rigidly assembled bearing it really means a lot.  I mean across your crankshaft in your engine cases if the bearing bores are 2 or 3 thousandths out of alignment that applies at least an extra 2-3000 lbs of force to the bearings under normal operation.

Edited by 1987CR250R

Share this post


Link to post
Share on other sites

Well I did lightly lap the cases on a piece of true bar at work l. This is how I did it,

I used a dye on the sealing surface. Then stuck a piece of 400 grit paper to the true bar ( precision machine flat piece of material) with WD40 and used a figure eight pattern rotating the case every so often until all of the dye had diss appeared. This didn't take much work and the cases went together butter smooth and the crank spun like butter as well

Share this post


Link to post
Share on other sites

Well I did lightly lap the cases on a piece of true bar at work l. This is how I did it,

I used a dye on the sealing surface. Then stuck a piece of 400 grit paper to the true bar ( precision machine flat piece of material) with WD40 and used a figure eight pattern rotating the case every so often until all of the dye had diss appeared. This didn't take much work and the cases went together butter smooth and the crank spun like butter as well

lapidary and lapping aren't the same thing at all.

some of the posts seem unclear on that.

 

lapping will get something *absolutely* flat, as in 5 decimal places flat.

master carbide guage blocks are lapped.

 

a small stone can be used to remove nicks on a sealing surface.

lapping without knowing how is a good way to make a small problem

go away by irreparable  damage to the part. then you can buy another.

 

the main reason i'd do it is to refine a surface and flatten it.

you can dykem the surface and then lap with a charged lap, if you know

what you are doing.

 

a good primer on lapping can be found here:

 

http://www.brighthubengineering.com/manufacturing-technology/67363-a-guide-to-grinding-and-lapping-paste/

 

as for glass beading... if you want that look of fine grained texture, you can use walnut shells, or soda.

if you want it stronger, you can shot peen, but then you really can't penetrant inspect afterwards.

penetrant inspect for cracks, then shot peen.

 

or, just put it back together and go ride it.

Share this post


Link to post
Share on other sites

I didn't glass bead the cases, it's a cr250 so it has a center gasket, I know for a fact I didn't take much at all off of the cases, I also know they are flat sealed.

For cleaning I bought some aluminum wheel cleaner and they came out great!

I didn't glass bead the cases, it's a cr250 so it has a center gasket, I know for a fact I didn't take much at all off of the cases, I also know they are flat sealed.

For cleaning I bought some aluminum wheel cleaner and they came out great!

Share this post


Link to post
Share on other sites
lapping will get something *absolutely* flat, as in 5 decimal places flat.

 

 

 

That depends on the surface it's lapped against.  Lapping makes two surfaces match each other, but there's no guarantee whatsoever that it will produce a flat surface.  An example is when people try to short cut a valve job by lapping a new valve to a worn seat.  The seat will be closer to true, but the valve will end up with a an off-square, off-flat wear pattern. 

 

This is less likely with a steel surface plate and an aluminum case joint, but there is still the question of keeping the shaft axes perpendicular to the joint, and if the practice is continued over time, the surface plate will have a "dish" worn into it and no longer be flat.  Lapping is a fine finish operation only, designed to allow two surfaces to mate more closely, and cannot establish or enforce flatness.

Share this post


Link to post
Share on other sites

Do not bead blast any machined surfaces.  NO EXCEPTIONS.  You will ruin things.  Lapping is a fine finishing technique.  It will not work if you are far off on flatness to start.

 

To truly get surfaces flat, thee is no substitute for scraping, but you do not really need to do that for machine fits. 

 

In fact...scraping is far more accurate than grinding.  In fact, some of the highest precision machine tools in the world are still hand finish scraped in climate and seismic controlled rooms. 

 

 

Skilled scrapers can achieve flatness of 50 millionths across the surface plate reference, assuming an AAA surface plate reference.  I have personally scraped items flat enough, that I can put my hads o the surface, and in 30s...the heat from my hand will pull the surface enough to cause it to pick up a different pattern on the surface plate when I ink it.

 

This really has nothing to do with engine cases...I just think it is cool how you can scrape something so flat with such a low tech tool...and the right skills.

Edited by Blutarsky
  • Like 1

Share this post


Link to post
Share on other sites

Do not bead blast any machined surfaces.  NO EXCEPTIONS.  You will ruin things.  Lapping is a fine finishing technique.  It will not work if you are far off on flatness to start.

 

To truly get surfaces flat, thee is no substitute for scraping, but you do not really need to do that for machine fits. 

 

In fact...scraping is far more accurate than grinding.  In fact, some of the highest precision machine tools in the world are still hand finish scraped in climate and seismic controlled rooms. 

 

 

Skilled scrapers can achieve flatness of 50 millionths across the surface plate reference, assuming an AAA surface plate reference.  I have personally scraped items flat enough, that I can put my hads o the surface, and in 30s...the heat from my hand will pull the surface enough to cause it to pick up a different pattern on the surface plate when I ink it.

 

This really has nothing to do with engine cases...I just think it is cool how you can scrape something so flat with such a low tech tool...and the right skills.

ohoh.... look out... the toolmakers are coming out!

 

yeah, we've gone way over the top on this thread.... i didn't even mention scraping... 

 

i came from three generations of machinists... my uncle used to hob his own

gears... there is "old school", and then there is "before the dawn of time".

 

and yeah, a lap will only be as flat as the lapping surface... those usually are pretty flat, however.

 

i used to work in aerospace and electronics, where a toolmakers microscope was your main

measuring stick....

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×