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Flywheel ring gear

Posted By Brian C Last Month
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Rustymachine
Posted 6 days ago
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This is the type of information that I find invaluable.  Thanks for taking the time to share the knowledge.

Matt


Tony Bullard (2/8/2019)
Brian, I don't know how to say this nicely but it's a good thing your welder didn't try any harder or he really could have screwed this up more. It's not to late. This can be repaired. I suggest taking it not to a welding shop but to a machine shop where they do machine repair. They will understand how important it is to maintain the correct shrink fit and also keep the correct tooth pitch through the weld section.  There are many ways to do this repair and each will use his own. The following is a way I may have done it.

First thoroughly clean the flywheel and ring gear, V out the repair area to remove the bad weld and stressed metal and make room for the filler metal.



Get a pitch reference 180° from the break by clamping two 1/4" dowels to the gear teeth about 4" apart. This will be used to set the pitch in the weld area. It might measure something like 4.1234".

On a CNC miller make a gauge block about 3" long with the inside gear radius on the outside and the outside radius on the inside. This will be used to locate and secure the gear while welding and to ensure all excess weld is removed from the inside.

With one clamp clamp the gear on the right side to a FLAT plate. Clamp the gauge block to the right side gear. Clamp the  two reference dowels to the gear. Set the spacing to the reference and clamp the left gear to the plate and to the block.

Tack weld the root of the V with MG 600 TIG wire or equivalent.

With the block still attached remove the ring gear from the plate and finish welding the V. Grind off and excess weld. Put Prussian blue on the inside radius of the gauge block and rub it through the weld area. remove any high spots of excess weld that show blue.
There is probably about a .013" interference fit between the two components.  Heating the ring gear to 400°F, 325° change, will increase its diameter about .037" so it should fall on the flywheel with .024" of clearance.






jimfols
Posted 2 Weeks Ago
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Thanks for this Tony


Jim
Tony Bullard
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You will probably want to take the flywheel to the machine shop so they can verify the nominal 19” ring gear diameter you provided. This is where the shrink fit is engineered into and for this size it may be something like 19.010 to 19.015 and the ring gear is machined to nominal, 19.0000”. This is all spelled out in ANSI Standard Force and Shrink Fits ANSI B4.1-1967 (R1987) FN2 in Machinery’s Handbook.

FN 2 Medium drive fits are suitable for ordinary steel parts, or for shrink fits on light sections. They are about the tightest fits that can be used with high-grade cast-iron external members.


Tony
Brian C
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Thank you very much for sharing that information,  I appreciate it.
Thanks.
 Brian C
Tony Bullard
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Brian, I don't know how to say this nicely but it's a good thing your welder didn't try any harder or he really could have screwed this up more. It's not to late. This can be repaired. I suggest taking it not to a welding shop but to a machine shop where they do machine repair. They will understand how important it is to maintain the correct shrink fit and also keep the correct tooth pitch through the weld section.  There are many ways to do this repair and each will use his own. The following is a way I may have done it.

First thoroughly clean the flywheel and ring gear, V out the repair area to remove the bad weld and stressed metal and make room for the filler metal.



Get a pitch reference 180° from the break by clamping two 1/4" dowels to the gear teeth about 4" apart. This will be used to set the pitch in the weld area. It might measure something like 4.1234".

On a CNC miller make a gauge block about 3" long with the inside gear radius on the outside and the outside radius on the inside. This will be used to locate and secure the gear while welding and to ensure all excess weld is removed from the inside.

With one clamp clamp the gear on the right side to a FLAT plate. Clamp the gauge block to the right side gear. Clamp the  two reference dowels to the gear. Set the spacing to the reference and clamp the left gear to the plate and to the block.

Tack weld the root of the V with MG 600 TIG wire or equivalent.

With the block still attached remove the ring gear from the plate and finish welding the V. Grind off and excess weld. Put Prussian blue on the inside radius of the gauge block and rub it through the weld area. remove any high spots of excess weld that show blue.
There is probably about a .013" interference fit between the two components.  Heating the ring gear to 400°F, 325° change, will increase its diameter about .037" so it should fall on the flywheel with .024" of clearance.






Tony
Brian C
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http://forums.justoldtrucks.com/uploads/images/16bd0926-6140-4576-8855-0c35.jpghttp://forums.justoldtrucks.com/uploads/images/9884e464-a707-410e-b1be-3998.jpg
A little history - the engine sat for probably a year after I got it. Took the fly wheel off and sent it to a  truck repair shop to have it surfaced.  When I got it home it was so nice and clean I put  a coat of paint on the inside surface and the edge (looked pretty) and had it sitting on a block of wood overnight, The following morning I heard a loud bang, investigating, I found the ring gear split, encircling the block of wood. I then took it to a friend who has a welding shop and it was welded. I believe a nickel rod was used. It was then heated carefully and replaced on the flywheel. Several hours later while cooling I heard the familiar bang again.                                                                                                                                                                                                The number on the ring gear has not be identified. 
Thanks.
Brian C

Aaron
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Here is the site where i got a ring gear for a Nissan diesel, I was back and forth with them a few times about it as it was out of the country and they assured me it was the right one, it was, I don't believe it was on their site but I sent them the measurements and they had it.

http://www.ringgear.co.nz/Our_Products.shtml

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Tony Bullard
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"My 1091 cu. in. Hall Scott has a broken ring gear. "

Brian, what's broke about it? Did you look in to getting it repaired?
Even it it lost its shrink fit after repair it can be retained with bolts as dowels on the center line of the two members.


Tony
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Brian C (2/7/2019)
Quick update re Hall Scott ring gear.
The Cat 3306 seems to be the closest one I can find. Although the engine is tucked away in a corner I am going to try and mock up this modification in stages.
The O.D. difference is 0.614 in. - the H/S is the larger.
The I.D. difference is 0.94 in. - again the H/S is the larger.
I think the first thing I will do is get high grade 1/2" bolts and get the shanks turned down to a smaller (5/16?) dia. as the only load the starter has is cranking the engine over. 
My existing H/S flywheel will have to be machined so that the dia. is correct for the Cat ring gear. I may also have to look at the possibility of using a Cat Bendix drive.
Any suggestions are welcome. 
Brian C  


Brian I missed what you are trying to do whit the 1/2" bolts. If you are trying to relocate the starter you are going to have to deal with the pilot on the starter nose.




Tony
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I just remembered the name i wanted, the guy to check with would be Al Shuring he does ring gears, I haven't talked to him in a few years, I'll have to look for his number.
Do you have a part #


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