Lignum-Vitae Bearings vs. other wood bearings and composites Posted on Tuesday, June 27th, 2017 and is filed under News
This is an actual response to a customer who decided to use oak as a bearing material and then switched back to Lignum-Vitae. We are proud to bring this great material to the Hydro Industry.
Over a period of a couple of weeks the material failed. This is the owner of Lignum-Vitae’s response once he found out what the engineer had used. One week after this email the engineer checked and sure enough the oak bearing was damaging the shaft. The customer called and placed an order for Lignum-Vitae Bearings. It is our belief that Lignum-Vitae is the correct bearing for any application that needs to operate in water and be self-lubricating. Read below to find out more.
This is a real issue in that whatever equipment the white oak is running against will wear in a “groove” pattern. This is due to the silica present and density of oak vs. lignum vitae with oak growing at a rate of 6-8 growth rings per inch and lignum vitae growing at the rate of 50-60 rings per inch. This is very important in that as the wood wears down it will expose the “winter ring” and wear down the summer rings leaving the harder winter wood to begin digging at the steel shaft. With lignum vitae the density is so great and the rings so close there is zero winter or summer wood due to being tropical and no winter or summer wood is apparent. These attributes along with the guaic gum present make it the only viable wood choice for bearings.
The other thing I would worry about is by using oak with its grain running lengthwise, which makes it easy to split as firewood, will under duress split out and splinter apart while running. Lignum vitae has an interwoven interlocking grain bound by guaic resin giving it a (WORKING load of about 12,800 psi) vs. about (1,000 psi to RUPTURE white oak)!! I have seen shafts running locust, oak, hornbeam etc. for a short period of time cause inordinate grooving and gouging.
A similar phenomena takes place with some composites due to the bearing material is harder than the shaft requiring various treatments to the shaft to keep it from grooving. The other side of the composites is some are softer than the steel and will wipe or smear some of its material on the shaft causing it to have a “bump” while running. I am told often that this bump can be felt on the floor of the plant and even into the parking lot and when replaced with lignum vitae the operator can leave a nickel on its edge to demonstrate how smooth the equipment is running, in which I take great pride.
I am including an e-mail received just yesterday from an Army Corps of engineer operator for materials sent last year.
“We installed your lignum-vitae bearings on September 22nd 2010. We have not even adjusted them since. It is running very smoothly with no problems whatsoever. I don’t have any photos of the repairs at that time, but have a power-point of the Thordon which never worked & wore out in one year.”