Rebuilding tips for bonders

more rebuilding tips for bonders


photo courtesy of the HELC Group

Paying closer attention to equipment setup has found to be beneficial. Most rebuilders have some type of balancing machinery. Many members have questions how to gain repeatability out of their balancer. It appears many rebuilders are faced daily with problems cycling around converter balancing. After careful consideration and conversations with different shops, we have found some helpful hints that may encourage reliable balancing. First, location of the balancer should be considered vital and should be placed away from other machinery in which vibrations could travel across the floor. A good recommendation is to use machine isolators, or pads, under the mounting legs of the balancer. These pads consist of a plywood-type material coated with a thin layer of rubber, which prevents vibrations within the building to be transferred to the balancer. After isolation is assured, leveling the machine is a must. This is easily accomplished with a carpenter’s level or equivalent and by following the manufacturer’s instructions for installation. One consideration that may aid in installation is to locate the balancer in an area that is not prone to wind or severe drafts, such as doorways and windows. Secondly, be sure to balance the clutch and turbine as an assembly rather that separately. Each component may be off only by a few grams, and Rebuilding tips for balancing equipment when assembled, will cause a unbalanced condition. By balancing the components together and marking them, you are able to assure yourself that the internal components will not affect your balancing operation. The impeller and front cover may each be balanced separately, before converter assembly. This allows the rebuilder to index the two halves to obtain a cancelling-effect. For instance, if the impeller is five grams out of balance, mark the heavy side with a marker for identification purposes. Then balance the front cover. If the front cover shows an out-of-balance condition, again, mark the unbalanced portion. After assembling the converter, you may be able to line the marked spots across from one another to help cancel out the out-of-balance condition. This will help eliminate the need to add extra counterweight material.

Possibly the second most popular question asked by rebuilders is, “how do I achieve a perfect clutch bond every time?” The answer that is usually given is that achieving a perfect bond every time is unlikely, but failures can be limited by following a set of simple rules.

Most importantly, proper remachining of the piston or front cover, which ever surface you are bonding to, leaving a finish between 15 to 35 RMS (Most of the industry, especially Raybestos recommends a bond surface finish of 80-120 microinches Ra, which is 88-132 RMS.  The spec for the reaction surface should be 10-20 microinches RA (11-22 RMS). This is approximately the same as a vinyl record.

Next item of importance is cleanliness. The surface has to be clean. After washing the piston or cover in a high-pressure parts washer, wipe the surface with a dustfree type cloth or paper towel using MEK or, if you prefer, denatured alcohol. Small, undetected pieces of debris or oils can cause a bonding failure.

After checking the bonding temperature, which usually hovers around 400 degrees Fahrenheit and should meet your suppliers recommendations, the bonding process may begin.

Each piston or cover may require a different process time and experimentation may be needed. Also, be sure the bonder is located away from drafts, which can cause cool zones within the bonder. This is critical and holds more weight in the process than you may realize. One side of the die may lose its heat, possibly cooling to less than 200 degrees by exposure to a draft.

Finally, air pressure is one item that is commonly overlooked. A dedicated line with a regulator is a must. Shop air pressure is known to rise and drop 30 to 40 pounds between cycles. This can effect the holding power of the air cylinder that applies pressure to the clutch surface.

After following these procedures, it is recommended that you test the bond’s integrity by blowing air underneath the liner and/or occasionally, using a scraper blade, and try to remove the liner. If either method produces delamination of the liner, you should contact your parts supplier and explain your dilemma.

Found in issue November 2005