Needle roller material

[Jim Allen]

A great improvement can easily be made to needle rollers used in manufactured engines by changing the roller material to AISI M-2 steel. All sizes, metric & inch sizes are available. The rollers shown in the photo have been extensively tested at RPM's beyond 32,000. Very low wear, no discoloration, no roller failures of any kind with oil content of 8%.

They are easily cut to length, chamfered or rounded on the ends.

Jim Allen

 

[Terry Keeley]

Hey Jim:

Are the stock needles 52100?

What advantage is there with M2?

 

[Mike Rappold]

A great improvement can easily be made to needle rollers used in manufactured engines by changing the roller material to AISI M-2 steel. All sizes, metric & inch sizes are available. The rollers shown in the photo have been extensively tested at RPM's beyond 32,000. Very low wear, no discoloration, no roller failures of any kind with oil content of 8%.

They are easily cut to length, chamfered or rounded on the ends.

Jim Allen

What are the five round slugs in the photo used for?

Mike

 

[dwilfong]

http://www.nskamericas.com/cps/rde/xbcr/na_en/TNSK_CAT_E1419c_Needle%20Roller%20Bearings.pdf

This is a link to some good info.

David

 

[Jim Allen]

Hey Jim:

Are the stock needles 52100?

What advantage is there with M2?

The rollers used in manufactured engines could be made of any steel that can be case hardened, such as the materials used to make dowel pins. They are probably not made of AISI E 52100 & M-2 or M-42 would be out of the question.

M-2 is a tungsten, molybdenum, vanadium, carbon steel that has the following characteristics; abrasion resistance, excellent toughness, good red hardness & easy heat treatment. After tempering ay 400 deg F, M-2 can have a hardness of Rc 64.

52100 is a high carbon, chromium, manganese steel that has the following characteristics; excellent through hardening, good wear resistance, good toughness & easy heat treatment. It is typically used at a Rc of 62 & is the favorite of many bearing manufactures. It will cost less per pound than M-2.

M-42 is a molybdenum, chromium, vanadium, tungsten, 8% cobalt, powdered metallurgy steel that has the following characteristics; great wear resistance, great toughness, a very uniform structure, superior red hardness & very high chip resistance, even when used at Rc numbers above 65. It cost more than either 52100 or M-2. It is a favorite steel for turbine bearings because of its high heat hardness capability.

I have throughly tested the above named steels in "caged roller assemblies" at RPM's exceeding 35,000 with oil contents of 7.25 to 8%. No pitting, surface erosion, roller fracture, roller dicoloration, roller or rod blueing were found.

Jim Allen

 

[Jim Allen]

A great improvement can easily be made to needle rollers used in manufactured engines by changing the roller material to AISI M-2 steel. All sizes, metric & inch sizes are available. The rollers shown in the photo have been extensively tested at RPM's beyond 32,000. Very low wear, no discoloration, no roller failures of any kind with oil content of 8%.

They are easily cut to length, chamfered or rounded on the ends.

Jim Allen

What are the five round slugs in the photo used for?

Mike

The five slugs are crank pins for the split type crankshaft used in many 26 cc gas engine. They are made of M-2 steel but I have tested some made of 52100 as well as M-42. All function without any problems at RPM's of 24,000 to 26,000 in my gas motors. Oil contents used are at 7.25%.

Jim Allen

 

[Jim Allen]

http://www.nskameric...%20Bearings.pdf

This is a link to some good info.

David

David,

This is excellent information. Also SAE paper #931561, which is an investigation comparing bearing steel rollers to ceramic rollers that are used in 2-cycle engine connecting rod big end bearings, is a very good read.

Jim Allen

 

[Terry Keeley]

Thanks Jim!

 

[dwilfong]

http://www.nskameric...%20Bearings.pdf

This is a link to some good info.

David

David,

This is excellent information. Also SAE paper #931561, which is an investigation comparing bearing steel rollers to ceramic rollers that are used in 2-cycle engine connecting rod big end bearings, is a very good read.

Jim Allen

thanks Jim always looking for good info. You a wealth of knowledge for are hobby thanks for sharing.

Where do you get your caged bearings from. Do you put new needles in the cages or are there some that have the right ones in it from the get go.

David

 

[Jim Allen]

thanks Jim always looking for good info. You a wealth of knowledge for are hobby thanks for sharing.

Where do you get your caged bearings from. Do you put new needles in the cages or are there some that have the right ones in it from the get go.

David

First, there is no manufactured roller bearing assembly that can be purchased with a retainer that can survive at the typical RPM's of our toy engines. Second, it can be easily seen by examining any roller bearing catalogue that the limiting RPM of a caged assembly is much higher than any comparable size uncaged assembly. However, the caged assembly will not be able to carry as great a load as the uncaged full compliment assembly.

The problem in our motors is not the load carrying capability but the high RPM. Only retainers that are very hard (Rc 63) with very high tensile strengths (300,000+ psi) will work. The reason for this is because if we consider the space that is left between any two rollers in the typical .90 cuin size motor, there will be a .025" wide pie shaped piece left for the retainer, measured at the center line of the rollers.

This number comes from the .3281" crank pin diameter & .0627" diameter rollers used in my .90 cuin size motors. By designing the retainer to accept two rollers in each window greatly increases the load carrying capability without limiting the RPM capability.

Unguided rollers will always develope a helix angle that is directly proportional to the rotating speed. Anyone who doubts what I have written above should run the uncaged roller assemblies found any manufactured engine at 32,000 RPM for two minutes! No amount of oil will keep these types of assemblies from having high wear, developing high heat & eventually failing!

Jim Allen

 

[Terry Keeley]

As always your insight and practical knowlegde is much apprecited!

Could you elaborate on this:

"Unguided rollers will always develope a helix angle that is directly proportional to the rotating speed."

I've found that CMB's with roller rods the needles tend to wear rather than the crankpin or rod, is this your experience?

 

[Jim Allen]

Could you elaborate on this:

"Unguided rollers will always develope a helix angle that is directly proportional to the rotating speed."

I've found that CMB's with roller rods the needles tend to wear rather than the crankpin or rod, is this your experience?

Terry,

The wear in CMB motors is probably due to the type of material used but it could also come from inadequate size, developing helix angle as the parts rotate, to much clearance & improper finish on the rollers, all of which can encourage sliding of the rollers beyond what will normally take place. I run M-2 steel rollers on a M-2 steel crank pin at very tight clearances, typically .0003" maxium. Both steels used are through hardened to Rc 63 to 65. Oil content never exceeds 8% with any RPM, the weakest part, the connecting rod, will allow (beyond 32,000).

The bearing engineers at INA made me aware of the helix problem, the correct clearance, the finishes on surfaces involved, the advantages of chrown grinding, roller end shape, proper retainer design, etc. During rotation, when using unguided rollers, the roller's axis of rotation will not be parallel with the axis of the rotating part. This phenomenon occurs even when the clearance in full complement assemblies is minimized. This will cause heat build up, high wear & failure if allowed to continue no matter how much lubricant is present! Heat build up DOES NOT come from two adjacent rollers rubbing aginst each other as they rotate in oposite directions; consider the total area that is in contact at this point during rotation!

Jim Allen

 

[Martin Hamilton]

Jim on my .21 motors for the last 30 years ive been making my cranks & never had a single failure either from breaking or turning in the hole. Ive always used 5mm needle rollers, nice & easy to get & cheap as well. This is with plain bronze in the rod. These are in record holding tether hydros. Martin.

 

[Terry Keeley]

Could you elaborate on this:

"Unguided rollers will always develope a helix angle that is directly proportional to the rotating speed."

I've found that CMB's with roller rods the needles tend to wear rather than the crankpin or rod, is this your experience?

Terry,

The wear in CMB motors is probably due to the type of material used but it could also come from inadequate size, developing helix angle as the parts rotate, to much clearance & improper finish on the rollers, all of which can encourage sliding of the rollers beyond what will normally take place. I run M-2 steel rollers on a M-2 steel crank pin at very tight clearances, typically .0003" maxium. Both steels used are through hardened to Rc 63 to 65. Oil content never exceeds 8% with any RPM, the weakest part, the connecting rod, will allow (beyond 32,000).

The bearing engineers at INA made me aware of the helix problem, the correct clearance, the finishes on surfaces involved, the advantages of chrown grinding, roller end shape, proper retainer design, etc. During rotation, when using unguided rollers, the roller's axis of rotation will not be parallel with the axis of the rotating part. This phenomenon occurs even when the clearance in full complement assemblies is minimized. This will cause heat build up, high wear & failure if allowed to continue no matter how much lubricant is present! Heat build up DOES NOT come from two adjacent rollers rubbing aginst each other as they rotate in oposite directions; consider the total area that is in contact at this point during rotation!

Jim Allen

So if I understand correctly the problem is that the needles tend to skew to one side and not run parallel to the crank pin?

Are the INA needles made of 52100? Are they available in a better material?

 

[Jim Allen]

Jim on my .21 motors for the last 30 years ive been making my cranks & never had a single failure either from breaking or turning in the hole. Ive always used 5mm needle rollers, nice & easy to get & cheap as well. This is with plain bronze in the rod. These are in record holding tether hydros. Martin.

A great deal of work was done by Carl Dodge in his .21 size speed plane motor. The motor has a pressed in crank pin & a titanium rod. The upper end is bushed & the bottom end has a pressed in keyed hardened sleeve. The hardened beryllium copper retainer in the bottom end has three .0312" rollers in each window. The engine is capable of much more than 42,000 RPM without breaking. Carl is one of three people to beat the Russians at a world speed class event in Kiev.

Jim Allen

 

[Jim Allen]

So if I understand correctly the problem is that the needles tend to skew to one side and not run parallel to the crank pin?

Are the INA needles made of 52100? Are they available in a better material?

Yes-No-No. The only way to get a better material for rollers is to purchase pre- hardened & ground blanks.

 

[Mike Rappold]

Jim,

What materail have you used to make the retainers out of?

Also are you grinding a radius on the ends of the needle rollers? If so how are you doing this?

Thanks in advance.

Mike

 

[Jim Allen]

Jim,

What materail have you used to make the retainers out of?

Also are you grinding a radius on the ends of the needle rollers? If so how are you doing this?

Thanks in advance.

Mike

I use C-350, 18% cobalt strengthened, Maraging steel to make the retainers. This is a tough, relatively soft (Rc 30), easily machined steel, usually delivered in the solution annealed condition & It is readily available. It will achieve full properties through martensitic precipitation aging at a low heat treatment temperature; 4 to 6 hours at 900 to 925 deg F; followed by an air cool. The steel has high yeild & tensile strengths, 340,000 & 350,000 psi; high toughness, ductility, & impact strenghts; high fatigue strength (10 to the 8 power at 110,000 psi); high compressive strength (388,000 psi) & high fracture toughness.

Because of the low temperature required to heat treat the steel there is very low shrinkage, minimum distortion & freedom from carburization or decarburization during heat treating. This is the strongest part in my motors. No retainer made of this alloy has ever failed or been replaced because of wear.

A grinding wheel is used to grind the radius on the ends of the rollers after they are cut to length. The correct radius is dressed in a grinding wheel with a diamond dresser. A radius gage is used to check the finished product.

Jim Allen