Let's Build a Mid Mount Idler Assembly

[312Hydro 474]

This is the part that I didn't get when I bought my used tiller. From what I've gathered,it's a commonly sought after part for the used tillers. Since I don't have the big bucks to buy it from Toro I decided to make my own. Having researched this awhile I've been able to approximate some of the dimensions . I scaled up some pictures that I came across. I'd really like the help from anyone who has an original for correct measurements. I will be using this exploded diagram from Parts Tree for Identifying the parts .http://www.partstree...1-57R10004-0002

Let's start with part 38 the mid mount idler support. So far, I know that it is 3/4" diameter round stock approximately 9+ inches long. I can cut to length after but for now I'll make it 10". It needs to be welded to 1/4" flat stock which I have determined to be 2"x3".If you have the correct dimensions please post and I will change it. We need to drill 3 holes in this plate. One 3/4" for the round stock to be welded to and two 3/8" holes on either side of the 3/4" for placement idler arm 58 with single or twin cylinder engines. Looking at this picture

I've determined that the 3/8" holes are about an 1 1/8" apart and 9/16" from the center of the 3/4 " hole. Could be wrong,let me know. For now I've cut the 3/4" round stock and will be getting the flat stock for the 2"x3" and the idler arm 58 which I think is 1/4" x 1 1/4"stock . Don't hesitate to chime in if you have dimensions! I'll also be giving credit for the pics once I know the original poster. Sorry ,as I just saved them over the past year.

[312Hydro 474]

Decided to get started and cut the 2"x3" from 1/4" plate.

Also cut the 3/4" round stock.

[312Hydro 474]

So today I started to assemble part 38 Mid Mount idler Support. Started by laying out the holes on the 2"x3" square that I cut last night. Didn't have a 3/4" drill bit but I made do with an 11/16". This meant that I would need to grind 1/32" off of the circumference of the 3/4" rod to make up for the smaller hole. Really not a problem anyway as it made a stronger weld. With a 3/4" drill bit I would have just chamfered the end.Also if your 3/4" rod is coated you will need to grind that coating off for a good weld. Start by placing a small tack on the assembled parts. Use your square to check for squareness. Usually the tack will pull the opposite side as it cools. Take a hammer and tap the opposite side so you have a right angle. Weld that side. Go 90 degrees and check and make square by tapping with the hammer. Check to be sure and tack it. Check and tack the opposite side. Usually I make the 3rd tack and do the 4th right after if I was square to begin with. This squareness is the most important thing that will affect your later work. If it's not right at anytime your tacking,grind the tack off and adjust, then re tack. Once the inside has your 4 tacks you can weld the outside. It won't pull out of square with those 4 tacks. After welding the outside finish welding the inner. Congrats,your first sub assembly is almost done!Later we will add the 2 spacers and the little thingy (borrowed that from Ian!) that engages the tach-a-matic.

I had time today to find part 15 Spacer No Longer Available from Toro or Parts tree. Tractor Supply Company had it with the pulleys. Pressed it into the pulley but after looking at the Diagram I may need to put it on the other side. Well that's about it and the pictures follow.

[312Hydro 474]

Rained today but was still able to get something accomplished. Laid out the "tabs" for the 3/4" rod that uses the tach-a-matic. Each tab is 2 1/4" long and 1 1/2" wide. Used 1 1/2" x 1/4" thick steel and drilled two 1/2" holes (which are 3/4" from the end and centered) and one 7/8" center hole. Again, if I had a 3/4" drill bit I would use it instead of the 7/8". Worked well though as it fit great and will weld solid. I laid these out in pairs and when finished I had six pieces. More than I needed but easier to make that way. Tomorrow I'll be getting the material to make the 3/4" locating bushings that are welded to the support rod with the tab. That will leave the fabrication of the arm that the pulleys are on and the belt guard and its support. The arm will be 1 1/4" wide and length to be determined. I'll be using 16 gauge sheet steel for the guard and thinking about 3/4" to 1" for the guard bracket. Here are today's pics

[Martin 2,131]

love it! a bit of home fabrication.........

with some patience, the right material and enthusiasm you can make almost anything for these tractors.

looking forward to seeing your progress.......

[312Hydro 474]

love it! a bit of home fabrication.........

with some patience, the right material and enthusiasm you can make almost anything for these tractors.

looking forward to seeing your progress.......

Thanks,Martin! The most difficult part of the build so far is verifying the dimensions. If I had one to measure from it would be so much easier. It will be interesting to see how close I am to the original when I'm done. I found out that a 4 1/2" grinder with a cutoff wheel is very useful . I used to just use it as a grinder but with the right disks it can do so much more. I like the Makita (7 amp) I have as it's similar to what the mechanics had at work.Plenty of power.The only major tools that I've used are the drill press and mig welder.

[312Hydro 474]

Not much of an update for today but it was still productive! I went out today looking for the 16 ga sheet metal and some type of bushing to weld to the 3/4 " rod for locating stops. While in Home Depot I went into the electrical department and had one of those moments where sunbeams shone down on the conduit! Then it really hit me. Hey,I've got tons of 3/4" conduit leftover from the paint booth build! Well, maybe not tons but........I did have pieces. Went home measured up 3/4" on the length ,got out the pipe cutter and in about 5 minutes had 11 of those things made. Fit great too! I'll be working on the bracket for the guard tomorrow and then on to the pulley arm. Almost there! Here's the pics:

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[312Hydro 474]

Update time! I'm a little late but I have some good info! I started to make the idler arm Part 58 and the guard bracket. The Idler arm is 1/4" thick , 1 1/4 " wide x roughly 11" long at this point. I'll be giving you the final length after I have it mocked up with the tiller and belt installed. You can buy this at Lowes, Home Depot ,Tractor Supply etc. I decided to make it from the scrap plate steel that I had. I cut it by using the 4 1/2" grinder with a metal cutoff wheel. I used a piece of 1/4" flat bar that I had as a fence to guide the wheel for a straight line. Worked great and I never felt that it was an unsafe operation. You do have to make multiple cuts but it did work. Or, (saves time)you can just buy it! After cutting I laid out the pulley holes ( which are on the center line )measuring from one end ,3/4" to the first hole and 4 3/4" to the second. This gives you 4" between pulleys which seems to be right judging by the previous assemblies made here on Red Square.There will be one more hole for the tension spring Part 45 but we can add that later.Center punch and then drill your pilot holes. Use around an 1/8" drill bit and then you can finish with the 3/8" drill bit. Make sure to have your work secure before you start drilling. You don't want that chunk of steel spinning into your hand or worse. The idler arm is almost done but we still need to weld a 3/4"w x3/4"L spacer drilled with a 3/8" hole in it .This spaces the Idler arm part 58 away from the Mid Mount idler Support Part 38 . I am making the spacers only because I haven't found a source yet. I know some one must make them but I looked today and decided to keep going with my own.

Here is where I'm at now. A lathe would have made quick work of this! I don't have one, so.....I took a piece of 3/4" rod and took it to the drill press. But first I needed a way to hold it vertical and secure.I took a maple block and drilled a 3/4 " hole with a Forstner bit as deep as I could. Before removing the bit I had also clamped the wood so it would not move. Now , all I had to do was remove the wood bit and substitute my 1/8" or smaller metal drill bit. It would automatically be centered. Then, I just worked my way up by increasing the drill size in small steps. I also used a lubricant for cooling. I know this isn't perfect but to keep the 3/4" rod from spinning I used a pair of channel locks. Worked for me but do what you feel is safe if you decide to make your own. I am now ready to cut the bushings. But, I want the faces of the bushing to be parallel. I thought I could use the grinder but it needs to be a straight cut. Lots of ways to cut these, chop saw ,metal cutting bandsaw , lathe, whatever works for you. I'm taking them to a friend with a bandsaw.

All that is left to make is the Guard Part 57 and it's bracket. We'll cover the guard later but the bracket is made with 1/4" thick x 1" wide steel , I'll give you a length later when we get ready to make it. Well, that's it for now. Hope this didn't become to long but I plan on summing everything up at the end. Here are the pics-

[Anglo Traction 761]

Excellent Thread and subject Rich. I shall glean much from your work for when I make a Mid Mount Idler/Drive unit. I'm looking to have the option to transfer a PTO Drive to the left side of my C-120 in the future. Thanks

[smoreau 658]

Great work! I have some measurements from the older style tiller mid mount pulleys I got from one of Kellys nos units. I need to build one for my brother. Here are the pics.

[varosd 1,185]

great thread and as parts continue to disappear from shelves..more home fabrication will be the norm. keep up with the great photos!

[312Hydro 474]

Excellent Thread and subject Rich. I shall glean much from your work for when I make a Mid Mount Idler/Drive unit. I'm looking to have the option to transfer a PTO Drive to the left side of my C-120 in the future. Thanks

Your welcome, Glad I could help you out.

Great work! I have some measurements from the older style tiller mid mount pulleys I got from one of Kellys nos units. I need to build one for my brother. Here are the pics.

Thanks, That mid mount looks pretty strong since the bearing mounts on the 3/4" rod.You could just thread the end and weld it to the bracket.

great thread and as parts continue to disappear from shelves..more home fabrication will be the norm. keep up with the great photos!

Thanks, This seems to be a needed part 'cause they usually don't come with the tiller.

[312Hydro 474]

Mounted the tiller and drive belt to check measurements. I took a lot of time trying to determine the best position for the pulleys. This needed to be done before any welding could begin on the 3/4" locating spacers and the tach-a-matic tab. In the end this picture verified where things went.

Thank you to whoever owns this pic!

I tacked the 3/4" locating spacers while on the tractor, making sure to disconnect the battery before starting to weld. I then tacked the tab and removed the assembly to finish the welds. I put the assembly in the vice and leveled the end plate. I then measured the angle of the tab and found it to be about 17 degrees. I checked the mower deck tab and it was 22 degrees. I think any where in the 17 to 23 degree range would be ok. Maybe 20 degrees? It would be great to get some feedback on this.I also think a larger in diameter spacer might be better for the idler arm. I didn't like the 3/4" one I made as it seemed to throw the rear pulley out a little and the belt didn't ride in the center. I put in a stack of washers and once I had them even it seemed better with the belt tracking in the middle of the 2" idler. I still might try that 3/4" spacer again just to be sure. I still need to make the belt guard bracket , Guard , and bend the Idler arm in to wards the tension spring. Here's today's pics-

[ericj 1,578]

the pictures of the complete unit looks like a older C series unit and looks like you are trying to make the newer style. for the newer style 3/4 shaft if you had a quick attach rod from a mower deck laying around you could use that for ease of manufacturing. I had a guy make me one of the older style idler, but i gave him one to look off it came out pretty good

eric

[varosd 1,185]

Rich, on fleabay, there is repro rig just like you are building, if you construct a couple more...I'm sure you could sell them at the big show next month!! :rolleyes:

[312Hydro 474]

Rich, on fleabay, there is repro rig just like you are building, if you construct a couple more...I'm sure you could sell them at the big show next month!!

I saw that Don. It is like the example smoreau posted above. Whoever is making it is doing a professional job. I don't think you could tell an original WH and that repro apart!

[312Hydro 474]

Just a quick post . I found the solution to the idler arm part 58 mounting to the mid mount support part 38. I initially overlooked how it bolts together. That was why I didn't like the belt tracking. I will be adding the bushing part 47 and not using the stack of washers or my 3/4" fabricated bushing. Also, When I finish this build ,I'd like to put this in PDF form . Can anyone steer me in the right direction? I've used PDF's but never made one. I want to be able to use text,photos and diagrams. Then I can post it at the end of the build. Any good freeware out there? Might take awhile to do but I think it would be worth it.

[312Hydro 474]

the pictures of the complete unit looks like a older C series unit and looks like you are trying to make the newer style. for the newer style 3/4 shaft if you had a quick attach rod from a mower deck laying around you could use that for ease of manufacturing. I had a guy make me one of the older style idler, but i gave him one to look off it came out pretty good

eric

Thanks Eric! That's a great idea! It would make it fit perfect and much easier to weld. :text-thankyoublue:

[312Hydro 474]

Okay! Spent the last couple of days in the R & D lab! Not only did I solve the spacer problem, but I also got some seat time today tilling (testing) .First I need to go over some construction details. Lets start again with the Idler arm part 58 and its spacers. The front 3/8" pulley hole needs to be re drilled to 1/2"Then slightly enlarged with a Moto tool so the 3/8" I.D. spacer will slip into it(part 47). If I had a 33/64 " drill bit I probably would not have needed to MotoTool . But I didn't so....

This is for the 3/8" I.D. x 1" long spacer part 47 . This spacer also has a 1/2" O,D, which means the 3/4" inch idler arm spacer needs an I.D. slightly larger so that the 2 spacers will fit together.

The 3/4" spacer also needs to be slightly less than 1" long to allow the Idler arm to rotate freely.When you tighten the 4" pulley bolt the arm will be able to move and the 4" pulley will be tightly held but can still rotate.The outer spacer was then welded to the idler Arm Part 58.I bolted the parts together with the spacers in order for everything to be lined up when it's welded.

Make the first tack and then make the second on the opposite side. Finish by tacking the 3rd and the 4th opposite from it, Now you can remove the Idler arm and the inner bushing and 4"pulley. You are now ready to finish welding the idler arm spacer,Weld between the tacks, a 1/4 at a time. You want to try not to put too much heat into it at one time. Even being careful, the arm will pull from welding this spacer.I did all three and had about a 1/16" deflection after welding. No problem though, it can either be pressed flat or using a BH ( Big Hammer) , Forcefully tapped flat again.You will also need to drill-MotoTool the arm and bushing hole again for the 3/8 I.D. 'spacer. Just takes a little work.

We are now ready to bend the front of the Idler Arm towards the tension spring. I bent the arm 2" to the left once I had it heated with a torch. You could also bend this if you have a press. Measure 7" from the flat idler end and this is your bend mark.Heat and bend.

You can now drill a 1/4" hole close to the top of the front for your tension spring. I measured 3/8" in and 3/8" down,center punched, then drilled the 1/4" hole.

This brings us to the last part for the idler guard part 57 , the bracket.

I made the bracket from 1/4" steel 1" wide and 11" long. I started by measuring 2 1/2" from the end and marked for my 1st, 90 degree bend. Using a torch, I heated both sides,made my right angle bend and let it cool.I then measured 2 1/4 " and made my bed mark. Heat, bend , let it cool. Will continue the bracket tomorrow.

Lastly, some pics of it mounted on the 312H. My son and I took it to the garden to test it out. I still don't like the back pulley but the belt never came off as we tried different tilling depths and we gave it at least 1 hour working time.The belt to me should track in the middle of the flat idler, instead it is near the outside edge. Still thinking about this, but I'm very happy with the results so far. We'll get the bracket and pulley guard finished and then get back into this.

[312Hydro 474]

Just thought I'd post up on the flat idler alignment. I did a search this morning and found my answer here- Thank you, to daveoman 1966 ! I decided to use the washer idea as it makes it adjustable for any situation. If I bend the arm ,it will not be adjustable to the left. I only added 2 additional washers and the pulley lined up perfectly with the belt tracking in the middle.Spent another hour tilling and the assembly tracked straight and true! I'll get pics and a measurement up later. I'm also curious to see if the other 2 assemblies track the same. I'm betting they will and will get the washer treatment too.

[312Hydro 474]

Finished the bracket for the shield and welded it on to part 38 mid mount idler support. Part 38 is officially done! All that is left is the shield which will be made this weekend. Let's pick up where we left off by cutting the bracket to 2 1/2 " on both sides.

Bevel the bracket for welding on 1 side , all 4 edges. Then layout and center punch the holes for the 1/4" screws. I then drilled with #7 drill bit for tapping 1/4-13 coarse thread screws.The first hole is 1/2" down and the second is 2" ,both on center. This gives a spacing of 1 1/2" .

Drill the bracket before welding.

Some pics of the finished mid mount assembly minus the pulley shield.

[KC9KAS 4,741]

Your work has been well doccumented and looks great.

Once painted, it will look like a factory made set-up.

[312Hydro 474]

Your work has been well doccumented and looks great.

Once painted, it will look like a factory made set-up.

Thanks! Hopefully the instructions are complete to build one. I'll be working on the shield next.

[Lars 526]

Realy good work/fab on that.. it is a lot of work to build one. :)

[312Hydro 474]

Thank you, Lars! I hope I didn't discourage anyone by trying to show every step. If you take it in pieces it really won't be too bad. Now I just need to finish that shield. Anyone have a picture of the shield in a straight on view?