Very clean work, Stew!
Tube Frame Mower Deck Gearbox Roll Pin Modification
Posted May 29, 2018 - 06:09 PM
- Sawdust, 29 Chev and logmillingman have said thanks
Posted May 29, 2018 - 08:25 PM
- 29 Chev said thank you
Posted May 31, 2018 - 06:54 AM
Nice work . All the years that I mowed with my 1556 never once did I break a pin. I used to tow my leaf vac behind it sucking up leaves and grass. i wonder why some break and some don't. You did a great mod on yours I hope this last one works for you.
- KennyP, Sawdust, 29 Chev and 1 other said thanks
Posted June 01, 2018 - 08:31 AM
I wonder why some break and some don't.
That is a question that I have not found a definite answer on but I do have a few theories given my experience.
I believe the original roll pin in the smaller gear was originally just a regular roll pin and at some point it was upgraded to a different part number that was a spiral wound roll pin to give it a bit more strength. I have tried using a spiral wound roll pin and found they do last longer but will eventually break - when they do break they usually come apart in little fragments first which results in the fragments getting chewed up in the gear teeth as can be seen by the marks in some of the gear teeth. The fact that the roll pin was upgraded would perhaps indicate that the pin was not anymore than adequate to drive the design. Add to this the fact that my spindles were set up with roller bearings initially which some people feel takes more power to drive would result on more load on the roll pin.
The gear location on the output shaft is such that the contact area between the shaft and the gear would be constantly immersed in gear lubricant under normal conditions resulting in very little friction between the shaft and gear whereas the input shaft gear is high enough that this would not be the case - this would result in the output shaft gear rotating on the shaft easier stressing the roll pin more than in the case of the input shaft roll pin. Some people have speculated that the holes in the shaft and gear for the roll pin get worn resulting in a loose fit for the roll pin - I replaced the output shaft with a NOS shaft and verified the roll pin was a drive in fit in the holes in the gear and shaft but did not notice any difference in the roll pin breaking.
The output shaft gear is turning at a higher RPM in relation to the input shaft gear and as a result the load on the pin in the lower gear would be greater - add to this that any thing causing a load on the blades (twigs, clumps of grass, etc) and the first load point that would be transmitted through the belt to the output pulley would be the roll pin on the lower gear.
The fact that some people cut the grass oftener than others and have lawns that are consistent grass density wise which would result in less load on the roll pin - I will be the first to admit that I don't always cut the grass soon enough and as a result some of the lawn areas can be quite thick which takes more power to cut (again resulting in more load on the roll pin).
Backlash in the gears could also be a factor as noted by other members comments as well as the straight cut gears in my gear box versus the newer helical cut gear designs.
Please note these are only my opinions. One thing I have noted is that I have never had the roll pin that retains the gear on the input shaft break - I would think that if there was a problem with the gearbox (shaft alignment, gear alignment, etc.) that eventually the input shaft roll pin would have broken at some point as eventually it would have become stressed as well as the lower roll in was replaced with a new one each time.
I would never recommend replacing the input shaft roll pin with a solid pin as this could result in damage to the gears, gear box or other items if something jammed.
- logmillingman and Doug E. have said thanks
Posted June 06, 2018 - 05:06 PM
Apparently my engineering skills were not as good as I had hoped. Today the sun was shining so this afternoon I started cutting grass - got about 3 hours of mowing completed when I heard a sound I did not like coming from the deck. Shut things down and saw I had gear lube leaking around the gear case so I headed to the shop, removed the deck and took the gear box apart. The retaining clip appears to have broken and the sheet metal tab broke as well allowing the pin to come out of the gear. The gear lube came from a hole where a piece of the gear case has been broken out by the head of the pin. Going to have to see if I can find another gear case and come up with a better solution to hold the pin in the gear.
Edited by 29 Chev, June 07, 2018 - 06:49 AM.
- logmillingman and 637Yeoman have said thanks
Posted June 06, 2018 - 06:25 PM
ClassicBolens who is a member on here can help you with a replacement gear case or all the parts needed to build one
- 29 Chev, logmillingman and 637Yeoman have said thanks
Posted June 06, 2018 - 08:34 PM
Sorry to see that happen to your gear case stay with it I know you will come up with a good solution and get it working good as new.
- 29 Chev said thank you
Posted June 07, 2018 - 11:37 AM
Was searching on the internet to find a better way to retain the pin and found an interesting listing on ebay with pictures of a complete helical gear box set up. https://www.ebay.com...pcAAOSwXtNaWDCQ
It looks like a solid pin in the lower gear on the output shaft with a knurled end to retain it as per the attached picture. I am wondering if anyone who has had a tube frame mower gear box apart can tell me if this was an original pin set up they have encountered in the later tube frame decks or if someone has replaced the roll pin with a solid pin? If Bolens went to a solid pin when they started switching over to the helical cut gears it might explain why the later mower decks that used the helical cut gears did not give much problem with the pin breaking. I looked at the parts break down for a 18423 model deck but it lists the pin for the lower gear as 1185218 which appears to be a roll pin given the images I can find.
Edited by 29 Chev, June 07, 2018 - 06:30 PM.
- logmillingman said thank you
Posted June 07, 2018 - 05:43 PM
I had a look at the gear case where the piece was broken out today after I got the area cleaned up - didn't see any serious cracks that would affect the integrity of the case so I decided to try a repair to it that may or may not work. I do not have the correct gas or a spool gun for my MIG to weld aluminum so went with an alternate plan - if this plan doesn't work out I can still take the gear case to someone to have a plate welded over the hole which would be the proper way to repair it. I made a plate out of a piece of 1/8" flat steel and shaped it to conform to the gear case area around the hole - I thought about using sheet metal but was afraid it might not hold its shape as well as the 1/8" flat steel. Once it was bent I drilled four holes in it so I could attach it to the gear case with some 10-32 machine screws. Using the holes in the plate I drilled four holes in the case and tapped them for the screws. Then I drilled out the holes in the plate so the screws would go through them, cleaned the plate and gearbox with brakleen and let dry and then I put on a layer of RTV around the hole. Set the plate in place and threaded in the screws till they were finger tight and let the RTV set up. While the RTV was curing I turned a new pin for the lower gear on the lathe - I think I will run a bit of weld on the end once it is installed which should keep the pin from coming out - may tack bot ends of the pin to the collar of the gear so even if the pin breaks it won't come out and chew up inside of the gear case. The weld will be a bit of a pain as it will have to be ground if I ever want to remove the pin but it should prevent the pin from coming out when the gear is spinning around. I got to thinking about why the clip and the sheet metal tang may have broke - it may have been caused by vibration because the head of the pin and where I welded the sheet metal tab on would not be balanced - the PTO on a tube frame turns about the same speed as the engine so at 3000 RPM it may have had some wired forces being applied to things. With the end of the new pin welded it should offset the weight of the head of the pin and things should be better balanced. Once I had the pin made I tightened the screws and used a chipping hammer to peen the ends of the screws so hopefully they will stay tight and not come loose. Will let the RTV set up overnight and hopefully start putting the gear box back together tomorrow and then time will tell if it leaks, seeps or holds gear lube.
- logmillingman said thank you
Posted June 07, 2018 - 08:54 PM
The patch ought to work OK. You have nothing to lose by trying. I did about the same thing to a B&S 8hp. that let the rod out the side. Dad got a couple more years use from it after I pieced it back together.
- 29 Chev and logmillingman have said thanks
Posted June 08, 2018 - 08:04 AM
It is worth trying to repair it Stew, those gear boxes are getting expensive. I don't know if this would work but I have used 3-in-1 rod for welding aluminum, and there was a product called Alum-a-loy for welding aluminum just using a propane torch that they used to advertise on TV some years back.
Good luck, hope it works.
- 29 Chev said thank you
Posted June 08, 2018 - 05:30 PM
This morning the RTV appeared to be cured so I put the lower shaft, bearing , thrust washers and gear back in and pushed the new pin in place. Would have loved to have knurled the end of the pin but I don't have the ability so it got welded on the bottom and tacked on the head - don't think the gear case could handle the pin coming out again. This way even if the pin breaks it should stay in the gear rather than the ends flying out and damaging the gear case any further. It will take a carbide burr on the die grinder to remove the welds if I ever want to remove the pin to take the gear case apart but this way the pin should stay put. Once the pin was welded I cleaned out any weld spittle out of the gear case and made sure the shafts turned freely - found a small bit of spittle in the one gear tooth so I removed it with a screwdriver. Then I bolted the back on the gear case, filled it with gear lube and then set the gear case on a block of wood for about an hour to see if there were any leaks. While I waited I welded some cracks I had found in the deck, sharpened the blades and cleaned the gear lube that had leaked out off the deck and belt. Around the one bolt hole where the gear case mounts there were a few cracks but I think I got them all. When I was done I checked the gear case and everything looked dry so I mounted the case back on the deck and mounted the deck back under the tractor. I temporarily left the belt guard off so I would have a good view of the gear case while I was cutting to see if any leaks showed up - not something I recommend as the belt guard is there for the safety of the operator and I believe it also gives the deck more strength when it is installed.
Went to start the tractor to try the deck out and when I turned the key all I heard was a sickening whine - turned the lights on and noticed a very faint red glow at the tail lamp - a quick check with the volt meter told me the battery had decided it wasn't in the mood to play its part in the mowing game any more so it got replaced with another one. Once the battery was replaced I fired up the tractor and finished cutting the grass for about an hour while watching for any leaks or seeps. Had a good look when I was done mowing and everything appears dry and the blades are still turning - so far so good.
Edited by 29 Chev, June 08, 2018 - 05:33 PM.
- KennyP and logmillingman have said thanks
Posted June 08, 2018 - 09:59 PM
Nice work Stew!
- 29 Chev said thank you
Posted June 28, 2018 - 07:10 PM
Decided to have a backup plan in case the gear case repair does not last or have some seepage. Contacted member "Classic Bolens" and he was kind enough to sell me a NOS gear case, bearing and seal kit, NOS helical gears and NOS input and output shafts. Took some pictures of the items - then I pressed the new bearings and seals into the case and applied a coating of grease to the seal lips and the bearing needles. With all the items new this gear case will probably outlast me (I hope).
- logmillingman said thank you
Posted June 29, 2018 - 03:29 PM
Got the larger gear installed on the input shaft - first time I installed it backwards so had to remove the roll pin and start over.
Decided to measure the thickness of the new thrust washers with the micrometer (appears they are approximately .061" thick) so I would have a reference point of what a new one should measure - I can use this measurement to see if my old thrust washers are worn if I have to take the old gear case apart and I can also check the thrust washers on the 38" deck I am repairing. Installed the thrust washers and the thrust bearing on the new input shaft along with some grease and placed it in the case. Then I installed the output shaft into the case and installed the thrust washers and thrust bearing along with a coating of grease on it. Marked the output shaft with a marker to know where the lower gear should be to align the roll pin hole in the shaft after I stuck a 1/4" punch in the gear and the hole - the hole on this shaft is in line with the lower keyway. I decided to use a spiral wound roll pin in the lower gear as I have had better luck with them not breaking as quickly. Started the roll pin in the lower gear and then I set the lower gear in place and slid the shaft in the rest of the way until the mark was aligned - then I installed the roll pin the rest of the way. As I was installing the gears I noticed that the shafts slid into them by hand so it appears the gears were not made to be a snug or light press fit on the shafts so the roll pins are doing the work of rotating the gears as the shafts rotate.
- Bolens 1000 and logmillingman have said thanks