USA-1 Nitro counter gear and shaft, dimensions

atrc

Well-Known Member
The engine runs!!
Only until the main needle assembly falls off :(
Seems JB Weld aint as fuel proof as I thought.
On to other solutions...

On the bright side, the counter gear assembly worked and stayed in place :D
You must have not mixed equal parts. I have used JB weld on nitro engines. To fix loose pressure fittings and holes in the crankcase. The surface has to be real clean for it to stick. Ruff the surface then clean it good.
 
ended up making a new carby needle mounting block from some scrap polyethelene, more reliable :)

As for the counter gear setup - it blew apart.
Wasn't that surprised though, as I had to fit a 10mm bearing into an 11mm gear boss - not much meat left around it, that's where it busted.

Seeing as I just completed my last exam this morning, and my new Traxxas gear parts arrived yesterday, I set to work..


Ground boss of large gear

bored bearing recess for 5x8x2.5mm bearing

bored same bearing recess on other end, bearing fitted


didn't stop to take any more pics, but the rest of the process is boring out the large gear to fit the smaller gear's boss (about 11mm), then pressing it in (must be a tight fit!).

I'll have to turn down the large gear width a bit, as it interferes with the clutch bell atm.. here's a pic of what happened to the previous clutch gear, btw..

 

atrc

Well-Known Member
ended up making a new carby needle mounting block from some scrap polyethelene, more reliable :)

As for the counter gear setup - it blew apart.
Wasn't that surprised though, as I had to fit a 10mm bearing into an 11mm gear boss - not much meat left around it, that's where it busted.

Seeing as I just completed my last exam this morning, and my new Traxxas gear parts arrived yesterday, I set to work..


Ground boss of large gear

bored bearing recess for 5x8x2.5mm bearing

bored same bearing recess on other end, bearing fitted


didn't stop to take any more pics, but the rest of the process is boring out the large gear to fit the smaller gear's boss (about 11mm), then pressing it in (must be a tight fit!).

I'll have to turn down the large gear width a bit, as it interferes with the clutch bell atm.. here's a pic of what happened to the previous clutch gear, btw..

There shouldn't have been a issue if you bored the hole just enough for the bearing only. If you bored the hole all the way threw then there won't be enough material for a good tight press fit. The smaller gear hub should be press fit to the big gear and you machine off the the hub side with the mounting screw. I have done this before and it works fine. The big problem here is that the larger origional gear is molded to the smaller metal gear. I suggest trying a smaller shaft size and trying again or you can also try borring a .005 smaller hole and heating the big gear untill it turns bright orange with a torch expanding it and then press fit the gear in.
 
There shouldn't have been a issue if you bored the hole just enough for the bearing only. If you bored the hole all the way threw then there won't be enough material for a good tight press fit. The smaller gear hub should be press fit to the big gear and you machine off the the hub side with the mounting screw. I have done this before and it works fine. The big problem here is that the larger origional gear is molded to the smaller metal gear. I suggest trying a smaller shaft size and trying again or you can also try borring a .005 smaller hole and heating the big gear untill it turns bright orange with a torch expanding it and then press fit the gear in.
Nah it all works well now with the smaller 5x8 bearings.
Wouldn't want to go with a smaller shaft ... as it'd be prone to more flex = gear failure.

In other news - oh dear, seems I've acquired another nitro USA-1 .......
 

atrc

Well-Known Member
The 5x8 bearings won't hold up long.I would suggest you not use anything larger than a 13 tooth clutch. I use 12 tooth and for power a 11 tooth with a 1.5 hp motor. Im useing a 1.7 hp motor and I am useing a 13 tooth clutch. That why your clutch drum went bad. Too much load.
 
The 5x8 bearings won't hold up long.I would suggest you not use anything larger than a 13 tooth clutch. I use 12 tooth and for power a 11 tooth with a 1.5 hp motor. Im useing a 1.7 hp motor and I am useing a 13 tooth clutch. That why your clutch drum went bad. Too much load.
Wrong.

Clutch gear failed because the counter gear failed (because of not enough wall thickness around the 10mm bearing).

Clutch gear is also under less load than a typical 1/8th scale vehicle due to the gear reductions (more than compensates for the large wheels).
 

atrc

Well-Known Member
Wrong.

Clutch gear failed because the counter gear failed (because of not enough wall thickness around the 10mm bearing).

Clutch gear is also under less load than a typical 1/8th scale vehicle due to the gear reductions (more than compensates for the large wheels).

I personly would have used a needle bearing more support with a 10MM bearing There just isn't enough to support a smaller size bearing like that.
 

Bryonfunderburg

Well-Known Member
just eliminate the counter gear all together.and get a motor with 2 to 3 hp. i did on all but 1 truck that has 3 bs-84 nip for the remaining life as a shelf queen cuz they will even break there.lol

mp6 international / usa 1 is getting close now..... i F king love the builds









the steering plates jim made the bottom left one

 

atrc

Well-Known Member
just eliminate the counter gear all together.and get a motor with 2 to 3 hp. i did on all but 1 truck that has 3 bs-84 nip for the remaining life as a shelf queen cuz they will even break there.lol

mp6 international / usa 1 is getting close now..... i F king love the builds









the steering plates jim made the bottom left one

All you got is 3 Bs84 sets:p I have 8 NIP and 4 used sets.:D tons of spare parts. I haven't stripped a gear now that I switched the bearing for the counter gear to a needle bearing. I run a 2 hp motor now. I don't want speed.
 

Bryonfunderburg

Well-Known Member
this truck is running 13 toothbells with a 48 tooth main gear.the other twin is running 18 toothbells and a 52 tooth main gear. for speed
 

Bryonfunderburg

Well-Known Member
i dont need them because i dont run the one truck i have that has a CG because it is new!

All you got is 3 Bs84 sets:p I have 8 NIP and 4 used sets.:D tons of spare parts. I haven't stripped a gear now that I switched the bearing for the counter gear to a needle bearing. I run a 2 hp motor now. I don't want speed.
 
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