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T-Head

How New Antique Engine Insert Bearings are Machined and Babitted

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Mercer-I.jpg

We are posting this to help educate the old car public about machine work on their engines.

We are not looking for or taking in any work but have decided to share how it is done in case

you run into needing to have to do something similar on your own car.

In our machine shop at The Old Motor our main work is rebuilding early vintage sports and

racing engines. We are doing a special set of posts on rebuilding a massive 784 cubic inch

1910 Thomas-Flyer engine and how we machine new insert bearings. We will also be covering

babbitting, align boring and connecting rod boring.

Above is a Mercer Raceabout crankcase being align bored in preparation for new insert beaings.

The photo below shows a new insert bearing shell being machined from bronze stock. It is one of

10 photos in a post that we have up now showing how it is done at theoldmotor.com

ThomasIV.jpg

Edited by T-Head (see edit history)

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Few people have the chance to view the inside/underside of a T-head Mercer, and it would be nice to have such a line-boring machine which is good to set up and will do a quality job quickly. You may think I am a mechanical pedant, but the combination of this sort of boring machine and crankcase is in contempt of the golden rule. The cylinder block or blocks should always be bolted to the crankcase is if for service. Aluminium crankcases in particular are quite plastic, and if there is distortion when the bearings are align-bored, then assembled they will be out of alighnment. If out of line by more than the thickness than the oil film, the crankshaft will bend as it revolves, and it may eventually break. I had the engine of my 1918 Mercer rebuilt in the early 1970's, and unbeknown to me, this was done. It took about 3000 miles to break the crankshaft. That is why I always do my own work. The old hand operated unit I have is not quick to set up or use, but it is reliable. I avoid doing this sort of work for other people.

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Few people have the chance to view the inside/underside of a T-head Mercer, and it would be nice to have such a line-boring machine which is good to set up and will do a quality job quickly. You may think I am a mechanical pedant, but the combination of this sort of boring machine and crankcase is in contempt of the golden rule. The cylinder block or blocks should always be bolted to the crankcase is if for service. Aluminium crankcases in particular are quite plastic, and if there is distortion when the bearings are align-bored, then assembled they will be out of alighnment. If out of line by more than the thickness than the oil film, the crankshaft will bend as it revolves, and it may eventually break. I had the engine of my 1918 Mercer rebuilt in the early 1970's, and unbeknown to me, this was done. It took about 3000 miles to break the crankshaft. That is why I always do my own work. The old hand operated unit I have is not quick to set up or use, but it is reliable. I avoid doing this sort of work for other people.

Ivan, yes engines are quite flexible and what you are seeing done here is the preliminary line-boring to fit new insert bearings. After the new bearings are babbitted and installed they are again line-bored with the cylinder blocks attached and if not we use torque plates that we have made up.

We also always check the flatness of the top of the crankcase and the bottom of the cylinder blocks and correct if necessary. We have found this to be much more of a problem causing strain and warpage of crankcases. We check and eliminate thais as it can cause cracked crankcases and cylinder blocks down the road.

We have tested alignment after we are done boring with this machine and have found it to be accurate to within .0003 (3 ten thousandths) over four feet.

Yes the older hand operated machines do work OK and we do have two them, but in day to day use, we find this Tobin Arp machine to hold better alignment and it is much more accurate and rigid.

What brand of align boring machine to you have Ivan? Do you do your own babbitting? How are your projects progressing in New Zealand?

Edited by T-Head (see edit history)

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