Flathead
Well-known member
Very true, but what is the point of going through all those modifications when the original will certainly last at least that long if not abused?
H&H Model A motor thrust bearing issue
- Thread starter edgar44
- Start date
Very true, but what is the point of going through all those modifications when the original will certainly last at least that long if not abused?
Benson, You are correct. The thrust 'washers' are really half washers that are on the bottom half 'Cap'. Although this is not ideal (Jim Brierly is correct) it does make it easier to replace without pulling the engine. With that said, I won't buy a H&H motor or have them rebuild one as I too prefer the thrust bearing the way 'Henry intended it'.
Thanks for response Edgar,
I saw one or two of these engines about 5 or 6 years ago, maybe longer than that, and wondered if they had a washer on the upper block side.
I did not take one apart to see and always wondered how long it would last!
I saw one or two of these engines about 5 or 6 years ago, maybe longer than that, and wondered if they had a washer on the upper block side.
I did not take one apart to see and always wondered how long it would last!
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Model A Man
Well-known member
I have what I believe is an H&H motor in my 1931 roadster that has been making quite a bit of noise. I’m planning on pulling the motor and take it a part to see if I’m capable of doing a refresh on the motor. I do know it has inserts and if they need to be replaced how do I find out what kind and size they are? I have a feeling the thrust bearing is also shot.
johnneilson
Well-known member
The only way to tell is to disassemble and measure for the bearings.
Many different combinations have been attempted, some better than others.
A major concern can be the inserts from some early cars. For instance, a common "B" rod insert used was from a Volvo, 1940's vintage. Not exactly something you can get at the local NAPA store.
You can contact me directly if you need some assistance, I have a database developed for the inserts and some old catalogs, back when the dimensions were published.
John
Fullraceflathead
Well-known member
To have a durable thrust bearing surface it would require a 360 ° surface in order to maintain the oils hydrodynamic wedge effect. Having only a partial contact surface breaks the oils hydrodynamic wedge and get some metal to metal contact.
johnneilson
Well-known member
Ummm, maybe not quite correct.
There are many production vehicles that do not have a full 360° thrust bearing.
I have set many cranks with an aluminum girdle and run directly on the alum surface 180°. Some of the clutches run have very heavy spring rates and require much thrust pressure.
The saving grace to these motors is that we have adequate oiling (pressure) to feed the center main and by default it keeps oil at the thrust surface.
FWIW, the center main thrust failures I have witnessed did not have adequate oiling (dipper type).
John
SAJ
Well-known member
Interesting g comment about breaking the hydrodynamic oil wedge. Yet tilting pad journal and thrust bearings are common in turbine and compressor bearings. Here is a quote:
The bearing itself consists of the journal region of the rotor and the bearing housing, containing the internal chamber of bearing and pivoted tilting pads. There is also a channel for oil entrance, an oil outlet and a thrust collar in the case of thrust bearings.
The bearing undergoes a hydrodynamic wedge effect as the rotor spins eccentrically inside the bearing housing at its normal operating speed. The rotor exerts a force on the oil enclosed between the rotor and the pads according to Newton’s second law and in accordance with oil’s incompressibility property.
The oil exerts a reaction force equal in magnitude on th6⁶e rotor resulting in raising it upwards. This action is called the hydrodynamic or wedge effect. In other words, the heavy rotating rotor is supported by the hydrodynamic effect (viscous force).
SAJ in NZ
The bearing itself consists of the journal region of the rotor and the bearing housing, containing the internal chamber of bearing and pivoted tilting pads. There is also a channel for oil entrance, an oil outlet and a thrust collar in the case of thrust bearings.
The bearing undergoes a hydrodynamic wedge effect as the rotor spins eccentrically inside the bearing housing at its normal operating speed. The rotor exerts a force on the oil enclosed between the rotor and the pads according to Newton’s second law and in accordance with oil’s incompressibility property.
The oil exerts a reaction force equal in magnitude on th6⁶e rotor resulting in raising it upwards. This action is called the hydrodynamic or wedge effect. In other words, the heavy rotating rotor is supported by the hydrodynamic effect (viscous force).
SAJ in NZ