Go Back   The Ford Barn > General Discussion > Model A (1928-31)

Sponsored Links (Register now to hide all advertisements)

Reply
 
Thread Tools Display Modes
Old 10-22-2020, 11:44 AM   #21
BRENT in 10-uh-C
Senior Member
 
BRENT in 10-uh-C's Avatar
 
Join Date: May 2010
Location: Eastern Tennessee
Posts: 9,583
Default Re: Time lapse Model A engine build

Quote:
Originally Posted by 1930artdeco View Post
I just want to be clear that 'fluidizing' the bearings means setting the bearing clearance to basically zero and (via the electric motor) 'melting' or 'wearing' the bearings to the correct size using the crank? This way they don't have to cut the bearings to size? Maybe it is just the term that is throwing me off.



I also am assuming that this is the best way to set the bearings (if you can) so that each bearing matches its individual journal/rod?


Thanks
Mike

Actually the bearings still need to be cut to size, but the burnishing method heats the casting only to the point where it becomes soft. This allows the bearing material to flow ever so slightly where it fits the journal pin with a closer tolerance. Additionally, the bearing material becomes harder after the process which increases the longevity of the bearing.






Hopefully you can read the information on these two pictures of a burnishing machine to better understand the process.

.
__________________
.

BRENT in 10-uh-C
.
www.model-a-ford.com
...(...Finally Updated!! )

.
BRENT in 10-uh-C is offline   Reply With Quote
Old 10-22-2020, 12:16 PM   #22
alexiskai
Senior Member
 
alexiskai's Avatar
 
Join Date: Apr 2018
Location: Mebane NC
Posts: 633
Default Re: Time lapse Model A engine build

Thanks Brent, this is very interesting. I wonder if anyone has figured out what duration and speed of "towing around a parking lot" is roughly equivalent to the 200 rpm burnishing operation they discuss in those pages. I guess you'd have to stop every X minutes and crank the engine by hand to try to sense when the force required had dropped enough.
alexiskai is offline   Reply With Quote
Sponsored Links (Register now to hide all advertisements)
Old 10-22-2020, 05:34 PM   #23
rotorwrench
Senior Member
 
rotorwrench's Avatar
 
Join Date: Jun 2010
Location: San Antonio, Texas
Posts: 12,039
Default Re: Time lapse Model A engine build

I'm not sure if Ford even peened the bearings after the babbitt was poured into the block. That may have been the purpose of the burnishing process. The crankshaft has a tendency to grow a good bit during that burnishing process due to heat generated. That would have made it problematic to even have the connecting rods attached prior to burnishing since the crank would grow too much and put them in a bind. The growth of the shaft would have been what set the clearance of the bearing and it would have insured the poured bearing would fit the block better since it's not really practical to tin a porous surface like a cast iron block even when new.

A lot of this stuff just wasn't done during rebuilding of engines outside the factory. Peening tools were mostly made for that side of the business in order to get the bearing to fit the block prior to align boring the bearings. Some of those peening tools look better than others for doing that job. There were also expandable rotary burnishing tools that were used by some in the rebuilding business. There was a lot of room for different tooling being used and different ideas about what procedures worked better than others. This leads to a lot of differing opinions on the subject.

All I know is that there weren't a lot of manufacturers doing engine bearings the same way that Ford was. Even Ford dropped babbitt bearing processes with the V8 LB engines in 1936.

This guy mentions the burnishing process in this link.
https://www.kmwford.com/what-is-a-babbitt.html

Last edited by rotorwrench; 10-22-2020 at 05:51 PM.
rotorwrench is offline   Reply With Quote
Old 10-23-2020, 09:04 AM   #24
BRENT in 10-uh-C
Senior Member
 
BRENT in 10-uh-C's Avatar
 
Join Date: May 2010
Location: Eastern Tennessee
Posts: 9,583
Default Re: Time lapse Model A engine build

Quote:
Originally Posted by rotorwrench View Post
I'm not sure if Ford even peened the bearings after the babbitt was poured into the block. That may have been the purpose of the burnishing process. The crankshaft has a tendency to grow a good bit during that burnishing process due to heat generated. That would have made it problematic to even have the connecting rods attached prior to burnishing since the crank would grow too much and put them in a bind. The growth of the shaft would have been what set the clearance of the bearing and it would have insured the poured bearing would fit the block better since it's not really practical to tin a porous surface like a cast iron block even when new.

A lot of this stuff just wasn't done during rebuilding of engines outside the factory. Peening tools were mostly made for that side of the business in order to get the bearing to fit the block prior to align boring the bearings. Some of those peening tools look better than others for doing that job. There were also expandable rotary burnishing tools that were used by some in the rebuilding business. There was a lot of room for different tooling being used and different ideas about what procedures worked better than others. This leads to a lot of differing opinions on the subject.

All I know is that there weren't a lot of manufacturers doing engine bearings the same way that Ford was. Even Ford dropped babbitt bearing processes with the V8 LB engines in 1936.

This guy mentions the burnishing process in this link.
https://www.kmwford.com/what-is-a-babbitt.html

I am not sure that is an accurate statement about the crankshaft growing quite a bit. My experience is that it grows the same as if it were in regular operation. The process of burnishing is to just barely tighten the cap nuts where the cap is barely rubbing. That is enough pressure to burnish the bearing. Since I cannot upload a video here, CLICK HERE to see if you can open this video that shows what is done, how much cap pressure, etc.


Tinning cast iron does nothing because the tin/solder will not stick to the cast iron. For that reason alone, Ford used holes to anchor the cast bearing to the cast block and or rear main cap.


The reason peening was not done at the factory is because the blocks were brought up to pour temperature in an oven prior to the pour, and were reintroduced into an oven for a slow post cool-down. Just like spin pouring connecting rods, in that production work allows processes for efficiency. Peening is necessary if you cannot keep the block hot enough to keep the cast bearing from prematurely shrinking.
__________________
.

BRENT in 10-uh-C
.
www.model-a-ford.com
...(...Finally Updated!! )

.
BRENT in 10-uh-C is offline   Reply With Quote
Old 10-23-2020, 09:28 AM   #25
30 Closed Cab PU
Senior Member
 
Join Date: Aug 2018
Posts: 2,332
Default Re: Time lapse Model A engine build

Wow, so much interesting info resulted from my basic question in Post 6. Quite a bit of it is over my head, but interesting anyway. I find it really interesting that processes/info used on 90 year old cars is still known. Thanks for sharing.
30 Closed Cab PU is offline   Reply With Quote
Old 10-23-2020, 11:50 AM   #26
1930artdeco
Senior Member
 
1930artdeco's Avatar
 
Join Date: May 2010
Location: Oakland, CA
Posts: 2,802
Default Re: Time lapse Model A engine build

Sponsored Links (Register now to hide all advertisements)
Brent, thank you for posting the ad about the burnishing machine. I learned quite a bit-most of this is over my head as well-but I learned that even in the 20's there were full pressure oil systems and shell bearings. I am guessing on the more expensive cars.

But, if burnishing the main bearings is more accurate than line boring I am surprised nobody has come up with an interesting way to recreate a burnishing machine. I am assuming it can be done with modern parts in a shop. Whether it is cost effective for a small time shop I don't know, but for a bigger shop?

Mike
__________________
1930 TownSedan (Briggs)
Still learning after all these years....
1930artdeco is online now   Reply With Quote
Old 10-23-2020, 12:04 PM   #27
alexiskai
Senior Member
 
alexiskai's Avatar
 
Join Date: Apr 2018
Location: Mebane NC
Posts: 633
Default Re: Time lapse Model A engine build

If you check out the video link in Brent's post, it's basically a burnishing machine, though less fancy.
alexiskai is offline   Reply With Quote
Old 10-23-2020, 12:43 PM   #28
BRENT in 10-uh-C
Senior Member
 
BRENT in 10-uh-C's Avatar
 
Join Date: May 2010
Location: Eastern Tennessee
Posts: 9,583
Default Re: Time lapse Model A engine build

Quote:
Originally Posted by 1930artdeco View Post
But, if burnishing the main bearings is more accurate than line boring I am surprised nobody has come up with an interesting way to recreate a burnishing machine. I am assuming it can be done with modern parts in a shop. Whether it is cost effective for a small time shop I don't know, but for a bigger shop?
Just so we are clear Mike, the bearings still must be line-bored as a way to ensure all three are coplanar. What the burnishing is doing is making the surface area of the bearing be closer in the dimension and shape of the crankshaft's journal.

Alternately to burnishing, the bearing clearances can be taken up by removing shims after running the engine 'XX' (-i.e.: small) amount of miles. The definition of 'XX' is different depending on the quality of the line-boring job and/or the Babbitt material composition. After operating the engine for the 'XX' period of time, the bearing clearances can be adjusted because the wear during that period has provided more contact area of the bearing against the journal pin. The time between the next adjustment period will/should be longer since there is now more bearing surface contact area to support the crankshaft.

There are still custom engine rebuilders that do still burnish bearings. Some do have specially-made machines that do the burnishing. I know of three or four creations that work very well.

Remember, the downside to this procedure is that it takes additional time. Time is money for most shops (-and most Model-A customers tend to be frugal ). The upside to doing this procedure is the bearing is denser and the contact area is much greater which adds longevity. It is very feasible for the first bearing clearance adjustment to be done at the 20k-25k mileage mark. Because of the babbitt density and thickness, with prudent driving habits (-no detonation, proper oil change intervals, etc.) a babbitted engine can outlast an inserted bearing twice-fold.
__________________
.

BRENT in 10-uh-C
.
www.model-a-ford.com
...(...Finally Updated!! )

.
BRENT in 10-uh-C is offline   Reply With Quote
Old 10-23-2020, 12:54 PM   #29
BRENT in 10-uh-C
Senior Member
 
BRENT in 10-uh-C's Avatar
 
Join Date: May 2010
Location: Eastern Tennessee
Posts: 9,583
Default Re: Time lapse Model A engine build

Quote:
Originally Posted by 30 Closed Cab PU View Post
Wow, so much interesting info resulted from my basic question in Post 6. Quite a bit of it is over my head, but interesting anyway. I find it really interesting that processes/info used on 90 year old cars is still known. Thanks for sharing.
It really is a simple comparison. If you look at the picture of the burnishing machine, you can see there is a heavy flywheel mass on the opposite end of the machine from the block. The machine uses the energy stored to rotate the crankshaft when the bearings are tight. Alternately, by towing the vehicle with the engine spinning, the energy transferred thru towing it is greater than what the starter s capable of generating.

One key part that I failed to mention, in that 3rd or 4th paragraph of the flyer, it speaks of how the mechanic can achieve 95%-100% of bearing contact. In other words, its like the difference between 100 men carrying a load vs 75 men. 100 men can likely do it much easier and for a much longer period than the 75 men can.
__________________
.

BRENT in 10-uh-C
.
www.model-a-ford.com
...(...Finally Updated!! )

.
BRENT in 10-uh-C is offline   Reply With Quote
Old 10-23-2020, 02:58 PM   #30
rotorwrench
Senior Member
 
rotorwrench's Avatar
 
Join Date: Jun 2010
Location: San Antonio, Texas
Posts: 12,039
Default Re: Time lapse Model A engine build

A lot of folks that do Model A and T engines don't burnish them like Ford did. They peen the bearings after they are poured to get them to fit well against the block then they align bore them to size. Ford was manufacturing more engines in a day than most folks work on in a year. Ford found their best way of building them as quickly as possible. Ford also had equipment that is unobtainium in this day and age. It takes longer to peen each bearing and prep for boring or reaming of the bearings but that is a practical way of doing things in the current business scheme of things. Some crankshafts have less meat on them now days so that takes more bearing babbitt to fill that gap. The thicker the babbitt gets may make the job a bit more complex than having nice new standard size parts to work with. A person could also use Time Saver lapping compound with a turning machine like the aftermarket unit in the brochure. The Time Saver compounds have been around since the model T days and have always been guaranteed to leave no abrasive embedded in the bearing surface.

On the subject of burnishing, I mentioned before that I don't know what the fit was at Ford when they were ready to start that process but I assume that is is safe to say that there likely wasn't much clearance in any of the mains when they started turning for the process. That shaft is going to heat up a way lot more with little or no clearance than a shaft journal with 0.0015" clearance. A properly lubricated bearing with 0.0015" of clearance will run relatively cool. One with no clearance and even with some oil for lubricant will damn sure get hot. The hotter it gets, the more that shaft will grow in every direction. The growth of the shaft is what forces the bearing material outward against the block and the main cap. The heat would cause the increase in plasticity of the babbitt and allow it to gain more clearance. How much clearance could be gained that way depends on how hot it gets and how much plasticity will occur without damaging the bearing. I have no idea what they actually ended up with for clearance. Ford had something figured out for that since they managed to manufacture multiple millions of these engines in the four years of production and likely a few thousand more after production stopped since they were produced up into the 40s for ag and industrial applications.

Last edited by rotorwrench; 10-23-2020 at 04:57 PM.
rotorwrench is offline   Reply With Quote
Old 10-23-2020, 03:04 PM   #31
Jeff/Illinois
Senior Member
 
Jeff/Illinois's Avatar
 
Join Date: May 2010
Posts: 2,242
Default Re: Time lapse Model A engine build

Interesting video fun to watch, thanks!

Also thanks for the info from posters on burnishing the bearings. I was especially interested in the fact that a PROPERLY done Model A with Babbitt bearings can and will outperform an insert bearing engine. Cool!
Jeff/Illinois is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Sponsored Links (Register now to hide all advertisements)


All times are GMT -5. The time now is 01:59 PM.