The continuing saga of Niksons 1402 IMP sn 129

[Snowtrac Nome]

turbinator you can't be married no way a wife would let you play in the shop that long with out wanting you to do stuff around the house.

 

[turbinator62]

Yep. 25 years now. The thing is, she never has to worry about a toilet that doesn't flush or a sewing machine that doesn't sew. I keep everything working. Plus a trip to Hawaii once a year.

I'm off the snowcat this weekend though - social obligations.

 

[turbinator62]

I finally ran out of excuses not to work on the tracks. I have been putting it off until I had a workable plan.

My old tracks were about 213 3/4 inches long. One track had 54 grousers and the other had 53. They also ran vey tight on the idler even with the idler at it's rearmost position.

I was pretty sure that the pitch of the grousers was 4 inches but I wanted to be certain.

To calculate the grouser pitch (laying flat) you need to know the minor diameter of the sprocket, and the drop distance of the grouser.

My sprocket is a little over 17.6 inches diameter at the tooth root and the grouser drop is about 1.125" . So 17.5" - (2 X 1.125") = diameter at the outside of the belt = 15.35" Multiply this times PI 15.35" X 3.1416 = 48.22" for the circumference at the belt outer surface. Divide this by 12 teeth = 4.018" Close enough to 4" for me. You can also see that the circumference at the root diameter of the sprocket would be 17.6 X 3.1416 = 55.29" Divide this by 12 teeth and you get 4.6". This would be important to know if you were going to use a straight grouser on this sprocket. The drop center grouser has a pitch of 4.6" as the drop portion spreads apart as it goes around the sprocket, but is only 4" at the surface of the belt.

The second part of the problem is to determine how long to make the belts.

The parts manual for my 1402 says that the track has 55 grousers. So 55 X 4 would equal 220 inches. But I want to have a second means of verifying that before I cut my belting.

From the above I know that the circumference at the outer belt surface is 48". The belt only goes around half of that so that distance is 24". The same thing needs to be done for the idler. My idler is 12" in diameter. 12" minus 2 X the drop of 1.125 = 9.75" Multiply this times PI for the circumference. 9.75" X 3.1416 = 30.63" Divide by 2 for the belt wrap distance. 30.63 divided by 2 = 15.31"

The total belt length will be these two numbers plus 2 X the sprocket to idler center distance. My center distance with the idler at it's center position is 90 inches. So 2 x 90" + 15.31" + 24" = 219.31". That is very close to the 220" calculated from a pitch of 4" times 55 grousers and within the margin of error.

Now my head hurts!

The belt will be 220 inches overall minus the lacing length of 5/8". So the cut will be at 219 3/8"

The next post will cover the drilling and assembly of the tracks.

 

[Snowtrac Nome]

I see you are a math wiz too glad some one likes it I had a hard time with it. I now know who to contact when I need to use math. your pitch turned out to be a small amount more than the 4 inches you called for. with new belts having your pitch a little tight will be a good thing, because as the belts stretch your pitch will also spread out closer to that 4.18 you came up with.

 

[turbinator62]

The actual flat pitch of drop center grousers is not as critical as it would be with straight grousers. Drop center grousers will rock and adjust (within limits) to the root of the sprocket as they go around it as long as the track is tight. Straight grouser pitch must be very close to the sprocket pitch or they will ride up on the sprocket tooth sides with the potential to jump a tooth.

 

[Snowtrac Nome]

good point never thought of that

 

[PrecisionMarine]

Very nice work on your 1402.
Sorry I'm late to the party or I'd have posted sooner. I went through much of what you did on my 1402 about 2 yrs ago, ended up with 55 grousers on mine as well.
http://www.forumsforums.com/3_9/showthread.php?t=46353

 

[turbinator62]

Before I could finish the tracks I had to make two more grousers. I had made one already and knew it wouldn't be fun.
I used a length of 3/4 by .120 square tubing and bent it using a torch to heat it to cherry red. It was progressively bent to match the contour of an original grouser. After bending I cut them to length and bent up the shoes from 1/4 X 3/4 flat bar. These were then tig welded to the bottom of the grouser. After drilling the mounting holes I bent up the tire guides from 3/16 X 3/4 flat bar and welded them on. The tire guides need to have a rounded top surface so I contoured them with an angle grinder and finished them with a flap sander. Voila! Two new grousers. I'm glad I don't have to make more! It took me about three hours including cleanup. Foundry work is not my favorite.

Next post will be assembly of the tracks.

 

[turbinator62]

Track assembly. Maybe I can finally get this thing back on the ground so I can move it.

After cutting the belting I used Flexco #45 alligator lacing. That is what was on the original tracks.

I followed the instructions in the lacing kit with the exception of using pliers to squeeze in a couple of prongs to hold the lacing in place so it wouldn't shift while it was hammered in. There is a rod that is used to keep the lacing from getting crushed while being driven. The first step is to drive it from both sides on a wooden block, then finish it on a steel plate or anvil. This will also peen the ends of the prongs slightly like a rivet to prevent them from coming out.

When doing the second end, make sure the lacing is positioned so the sides of the belt ends are aligned and to make sure that the lacing will align on both sides when the grousers are installed.

After measuring and marking the belt for drilling, I used a rotary punch I purchased from the belting company which worked real well. It is important to lube it with soapy water so it doesn't get hot. Don't use oil, that is not good for the rubber.

 

[turbinator62]

Final assembly finally!

The belts were measured, marked and drilled. I assembled them on a table with all new grade 8 hardware and new grouser clamps. This part actually wasn't too bad. It was nice to be able to stand up while doing the job but it still took about 5 hours. Thank God for electric impact drivers.

After assembly I mounted them on the cat. Those suckers are heavy! I can do it by myself but tracks for a bigger cat must be a real chore. Everything lined up well. Tension looks ok I think. The idler has a little bit of squish with 50 lbs of pressure in the tire. Both sides look the same. I think it is good to go!

I have to take a couple of days off from the cat to do a test and calibration run of a turboprop engine for an old customer. Then we will be at the cabin for a week.

 

[Sno-Surfer]

Great post and attention to detail! Really taking this one to the next level.

 

[DAVENET]

I can't believe you didn't sandblast & powdercoat all of those grousers before reassembling! They are so unsightly compared to the rest of the cat!








Just kidding
That's a ton of work you just knocked out in short order.

 

[turbinator62]

I thought about that too. I would have had to sand blast and paint 110 grousers just to have them ground up in gravel. I bought the cat for access to our cabin. We were using snowmobiles, but our road up the mountain is sometimes spotty for snow plus I have to make multiple trips with a cargo sled for all of the stuff my wife takes. You can't really take a snowmobile up because of the open areas of gravel and the drifts are too deep for a wheeled vehicle. The cat can do both. I will be keeping it in a cargo container at the bottom of the mountain on a friends property next to a road that is always plowed.

Retirement is GREAT!

 

[turbinator62]

Got a little more work done this week. The rear hitch was pretty bent up so I cut the old one out of the side plates and made a new one from an 18" piece of 3 -1/2" X 3/16 square tubing. I milled a square hole in both sides and welded in a receiver. Added a couple of tow rings as well. The step- bumper is from Harbor Freight. Also put on a couple of stick on led backup lights to light the step at night. They were about 5 bucks on eBay.

 

[turbinator62]

My 1402 didn't have a fuel gauge so I pulled the tank, cut a hole in it and silver soldered in a doubler for a sender after purging and filling it with water. Also made a set of side rails that can be used with the flat bed when the rear cab is off. It uses the same mounting holes as the cab and can be folded up for storage when not in use. The next project is to get the rear cab back on and make a back door.

 

[turbinator62]

Thought it would be a good Idea to put a carbon monoxide detector in the cab. They are only 20 bucks at Home Depot.

 

[turbinator62]

Spent a few days working on the back door. I wanted to replace the roll up plastic door with a steel and aluminum one made like the front doors. I even found a latch on eBay with the same key! I welded up the frame from 3/4 square tubing and used .040 2024 T3 aircraft aluminum I had left over from a previous project for the skin. The window is 3/16 laminated safety plate glass held in with polyurethane window sealant. The door is 36W X 41H.

 

[turbinator62]

This cat has a removable rear cab with a passageway between front and back. Nik used a roll up plastic cover over the openings which I retained for use when the cab is removed and the cat is used as flat bed. Most of the time the rear cab will be on the cat so I wanted to seal the two together to prevent weather and small creatures from getting in. The joint is in 6 parts made from .020 aircraft aluminum and held in place with Velcro so there will be some flexibility between front and back but still be easily removable. Each section has a flange to shed water that may come down between the cabs.

The only thing I have left on my list is the engine cover which will be challenging.

Looks like it will be done in plenty of time for winter.

 

[DAVENET]

Crazy impressive. Your improvements are going to end too soon (for us) since you already had a great platform to start from. I can only imagine the build if you had started from a real piece of crap!

It's great to see true skills being put to use 1) to keep an old machine alive & 2) to give the rest of us ideas for our own machines. This forum has certainly saved quite a few people from hacking their snowcats thru trial & error.

+1

David

 

[turbinator62]

Thanks for the compliments, but the real work was done by Nikson. You should have seen the cat when he bought it. You would have had to pay me to haul it away. He designed and built the entire cab, rebuilt the chassis and drive train and wired it in a matter of months, then used it all winter. He did all of that in about the same time that I have spent messing around with refinements I have made, and he did it in a small garage with hand tools to a high level of quality. I'm not sure I would have tackled a project that extensive.

Check out his forum http://www.forumsforums.com/3_9/showthread.php?t=58427 to see what I mean if you haven't already. His documentation through this forum and other photos are what convinced me to buy it with confidence.

 

[turbinator62]

Lest anyone be under the mistaken impression that I actually know what I am doing, read this. I had the cat parked in front of the hangar to remove the rear cab so I could work on the fuel tank. When I backed up to put the cab back on, because of the slight slope on the ramp I engaged the clutch with the transmission in reverse before I got out to keep it from rolling forward. After bolting on the rear cab I got in and hit the starter. The engine started instantly and before I could do anything I backed into my hangar door. It didn't even slow the cat down.

The damage wasn't too bad and is now completely repaired, (the cat wasn't scratched) but what a humiliating experience.
I now have a clutch safety switch wired in series with the starter solenoid so it can't be cranked unless the clutch is disengaged.

 

[Cletis]

AHHHH, sounds like one of my brighter moves!

Many years back I parked my field service truck in front of my garage after a 20 some hour work day/night. Next morning went out, opened the door and started it while standing beside it on the driveway. Must have been real tired the night before because I left it in gear (low). It proceeded to drive through the garage door, while the auto crane went through the roof. Quite a deal that was!!!

I had almost forgotten that brain fart!!!!!!

Real nice work on the cat, by the way.

Cletis

 

[Snowtrac Nome]

AHHHH, sounds like one of my brighter moves!

Many years back I parked my field service truck in front of my garage after a 20 some hour work day/night. Next morning went out, opened the door and started it while standing beside it on the driveway. Must have been real tired the night before because I left it in gear (low). It proceeded to drive through the garage door, while the auto crane went through the roof. Quite a deal that was!!!

I had almost forgotten that brain fart!!!!!!

Real nice work on the cat, by the way.

Cletis

that reminds me of an incident at the motor pool where I did that with a duce in the yard. it started hit the one in front of it, which caused that one to start as it was left in gear, and that one hit a third which also started what a mess chasing them down to shut down all 3. that is why you always leave the shut down cable locked out when shutting down a multi fuel duce

 

[JimVT]

jogging the starter is handy while putting tracks on

 

[turbinator62]

Here are some pictures of the finished exterior. I had to pull the engine due to a rough bearing in the chain case so I am working on that now.

The good news is that with the engine sitting on a dolly in the shop, it will be easier to fabricate the new air box to duct the hot engine cooling air down the tunnel. That is the last major project I have left to do. Lots of geometry.

Then just a few details and it will be done.

I'll post pictures on that as it progresses.

 

[turbinator62]

While changing the oil in the chain case I found a lot of metal and the oil smelled really burned. I pulled off the front bearing cap and race and it was totally trashed. I was afraid that there was also other damage. There was no option but to pull the engine. The gearbox cannot be removed from the engine in the chassis. Due to the front air inlet duct, I had to cut out the front cross member behind the engine to clear the drive shaft. Once that was done it was easy to disconnect everything and lift it out the door.

The good news was that the front bearing was the only thing that was bad. The other bearings, chain and sprocket looked good. I was able get a bearing on eBay for 22 bucks and a seal for 15. With gaskets the repair was only about $50. I love eBay.

 

[turbinator62]

This is the gearbox reassembly. I cut a keyway in the clutch shaft because I will have to extend it out to clear the air box which is 13-1/2 incheswide. I didn't want to ruin the original spline so I will machine an extension from 1-1/4 steel rod, broach a keyway in it and hold it on with a set screw. A new lever will be welded to the extension. It all went together nicely.

You can still see how hot the shaft got at the front bearing.

 

[turbinator62]

The Thiokol 1402 IMP was originally an open cab rig so having an air cooled engine was not a problem. When Nikson enclosed the cab, things got more complicated. He found that even in winter, he had to run with the doors open. He even added an RV roof fan and a large fresh air vent in front to get rid of the heat. It was my intention when I bought the cat to figure out how to duct the hot air (at least most of it) down through the tunnel and out the rear.

I was really dreading building the air box but when I had to remove the engine and rebuild the chain case due to a bad bearing it became much easier. The proverbial cloud with a silver lining.

The box is made from .040 2024 T3 aircraft aluminum, but it wouldn't have to be. I just happen to have a bunch of it laying around and I have the equipment to work with it.

I added a few rivnuts and nut plates to the engine to fasten the box to it. The holes in front are for defrost air vents to the windshield. I also had to make several baffles to block airflow from going where I don't want it. The exit area for the cooling air at the heads on the engine is about 60 square inches to open air. The area of the air box outlet is about 150 square inches. I should not have a problem with restricted airflow causing over heating.

With the gear case off I was able to make an accurate template for a bulkhead to block the air from going forward in the tunnel. This will be split horizontally at the centerline of the clutch housing and extend down to the belly pan just behind the rear engine mount. I will then fabricate a duct to force the hot air down and rearward through the tunnel. This will be screwed to the engine air box at the flange at the rear of the air box. The air box and duct will be insulated with engine compartment sound and heat insulation from NAPA.

I installed a carbon monoxide detector in the cab since there is always the possibility of an exhaust leak when an engine is running in a closed space. I think this would be cheap insurance on any of the cats with an engine in the cab. They can be had for 20 bucks at Home Depot.

The last two pictures are of the new floor over the fuel tank. The air duct will end at this point. You can see where I drilled out the rivets in the floor at the tunnel edge and replaced them with button head screws. This is where the air duct will fasten.

I have been sweating fabricating the air box for this cat since I bought it. I never really had any clear cut idea of how it was going to work. But once I committed to cutting metal and I could see how it had to go together it got easier, even though the work is tedious. I now have a pretty good idea in my head and just have to do it.

I'll have more as it progresses.

 

[turbinator62]

Just a few pictures from todays work. I finished the main air bulkhead that goes down to the belly pan behind the rear engine mount and machined the adapter for the clutch lever extension. I thought it would be a good idea to put a magnet on the chain case drain plug to collect any metal particles.

The engine is back in. While I had it out I also rebuilt the starter with a new solenoid and brushes.

This engine originally had a mechanical fuel pump which I removed and replaced with an electric one. I used the pump mount as a crankcase vent and plumbed it to the carb air intake. The crankcase was originally vented through the oil filler cap, which tended to create an oil mist in the cab. It now has a sealed cap.

I'll get started on the rest of the air box tomorrow.

 

[Snowtrac Nome]

you are doing a nice job of making that little Wisconsin a civilized little engine