Crawler Mafia UnderDrive Mod

[rock hard]

Originally Posted by EGRESSor

there are some Hyperion pinions that are beveled at the end , but the have the set screw in the beveled area
and i have some 10t bevelgears from duratrax http://www3.towerhobbies.com/cgi-bin...?&I=LXLFT2&P=7
they may work with the stock ring and some grinding
or with the duratrax ring gear (27T) and another spool http://www3.towerhobbies.com/cgi-bin...?&I=LXLFR5&P=7

The pinion I'm banking on is a 0.05 mod
and it meshes real good.

the losi pinion is 48 pitch

I went to lhshops and studied various bevel gears.
Nothing really caught my eye though.

Now I'm not a heli guy
but I think its called a tail rotor gear,its a bevel gear
but wrong material,though I will constantly be looking for
additianal options.

But hey,either way. Underdrive will be on a course near you soon,and
they will only be improving from here on out.

That along with the other inovative offerings from within our rcc community,
and you know this is gonna be a great season for the 1.9 class

[rock hard]

Originally Posted by EGRESSor

there are some Hyperion pinions that are beveled at the end , but the have the set screw in the beveled area
and i have some 10t bevelgears from duratrax http://www3.towerhobbies.com/cgi-bin...?&I=LXLFT2&P=7
they may work with the stock ring and some grinding
or with the duratrax ring gear (27T) and another spool http://www3.towerhobbies.com/cgi-bin...?&I=LXLFR5&P=7

I'll be posting pics soon,keep an eye out
set screw problem is not really a problem

[rock hard]

CrawlerMafia Underdrive mod

I again will layout the methode I used here for you.

Below will show how I use a 12t bully pinion with the right teeth(chamfered)

The only problem with this mod is I cant find these pinions in 12t anymore.

But if you happen to have some,you can put them to use,or pm me
as I would love to have them.


For starters I take a bearing from the axle and head to the garage to find me a drill bit that fits the bearing.



Then I find me a long 3mm bolt for the grub hole.
I have found this makes working with the pinion much easier.



Now I grind the bottom of the pinion just as close as I can to the grub.
I use a bench grinder for this.( see above pic )

Try not to let the pinion get to hot,so go for a bit then cool.
This isnt for your fingers,its best for the pinion itself.
If it gets to hot it could weaken the material.

So avoid using pliers and going gun-ho on it,take your time.
Dont worry about getting it perfect,you can fine tune it with the dremmel for the final touches.

Now I use the dremmel to cut the pinion down.
I cut at 6mm,then use the dremmel to get it down perfect.
It will be around 4.5mm when its done.


Now I use the drill bit to drill out the pinion.
I will place it in a vice for this.

Once drilled I place the pinion on the drill bit,and I'm looking to get the drill bit all the way within the pinion,like shown



The reason for this is I want alot of contact between the new output shaft and the pinion.

Yep thats right,that drill bit is about to be your new ouput shaft.
With the pinion in place I mark the back,then decide where I will grind my flat for the grub.

Then I just use the dremmel to make a flat like so



Now I cut the drill bit to my desire length and make a flat for the drive shaft

then I mount the pinion onto the shaft,so its easier to hold for touching up.

I then use the dremmel to open the teeth at the back a touch,and then go over the pinion with a wire brush on the dremmel to clean it up.


I would say your looking at 3 hrs totall time.
I place the pinon in the case with ring gear ontop,I then spin the gear slowly,
any place that feels to rough I clean up.

The grub will hit,just put your wrench in it and use the dremmel to grind it smaller.

When it was done it looked like this
12t pinion with new output shaft

[rock hard]

Ok see thats easy enough,now this same methode will work with just about any pinion you find that you think will work.
My buddy Mctwist has used this approach using an alum t-rex 450 pinion
though he used the original output shaft with success
I suggest you to make a new output shaft like I have discribed.

Otherwise,there is very little shaft actually within the pinion.
and only 1/2 of that shaft is actualy making contact,as it is flat on both sides.

But the output shaft is a snap to make,so no worries there.
The hardest part is the pinion,only cuz it is so darn small.

But the bolt in the side gives you somthing a little extra to hold onto while your working on it.

Also it takes away any risk the threads get bured.



Enjoy

[4xFord]

Hell yea that looks great.

[irok22s]

Originally Posted by rock hard

The 1.9 class is my favorite class to run.

1.9 is my favorite class too. I just wanted to say your underdrive mod is amazing. The quality of work done here is simply awesome.



The biggest question I have now is how do I get you to make me one.





.

[rock hard]

Originally Posted by irok22s

1.9 is my favorite class too.

The biggest question I have now is how do I get you to make me one.

send me a pm anytime

[irok22s]

Originally Posted by rock hard

send me a pm anytime

Sweet thanks PM sent

[rock hard]

Originally Posted by irok22s

Sweet thanks PM sent

You know though guys,its not that hard to do yourself,(if) ya have the time.
The only power tools used was a bench grinder a dremmel and a drill.

And you could use just a dremmel and drill actually.

[rockeater]

Great idea. Any update if these are gonna be produced? Thanks

[EvilTwin v2]

I love this mod. Since I've gotten used to it, it's become quite a handy feature. It's one of the things that helped me pull off the win at ECC.

[rock hard]

Originally Posted by EvilTwin v2

I love this mod. Since I've gotten used to it, it's become quite a handy feature. It's one of the things that helped me pull off the win at ECC.

glade your liking it,and congradualtions on the win at ecc
Wish I ciould have been there to take part in the carnage.


I'm extremely busy at work right now,when things cool down I will be making more of these in batches of 5.

[RickM]

Any word on how McTwists aluminum pinion is holding up? I am also planning on this mod and am thinking about playing with it in aluminum partially as a test drive. Knowing my hand work it is always good to have a spare floating around.

edit.

Welp. I just made an attempt at this mod tonight between tornado sirens and diving in and out of a closet. It appears I am a little off. Round about the set screw I kept getting a bit of a catch in my giddyup. worked on it a bit but still could not get the issue worked out. I think I got the pinion in a bit of a pickle trying to work it out.

[rock hard]

Originally Posted by RickM

Any word on how McTwists aluminum pinion is holding up? I am also planning on this mod and am thinking about playing with it in aluminum partially as a test drive. Knowing my hand work it is always good to have a spare floating around.

I would just talk to Gary and get him to make you one
I think Larry runs it also and it has held up for him.

[RickM]

Getting Garry or Larry to make me one would only prevent me front having a chance to grind off some skin with my dremel!!

I noticed your comment about the set screw. I had a perfect one going but the set screw got me turned around. I have purchased the smallest set screws available but I have not been able to try again yet.

Here is a question for you. When you talk about the gear mesh spinning cleanly how cleanly are you talking? Does it spin as smoothly as stock or do you expect it to be slightly rougher?

[asw27x]

would a 11t bully pinion work??
http://store.rc4wd.com/Bully-11T-Pinion-Gear_p_92.html

[rock hard]

Originally Posted by RickM

Getting Garry or Larry to make me one would only prevent me front having a chance to grind off some skin with my dremel!!

I noticed your comment about the set screw. I had a perfect one going but the set screw got me turned around. I have purchased the smallest set screws available but I have not been able to try again yet.

Here is a question for you. When you talk about the gear mesh spinning cleanly how cleanly are you talking? Does it spin as smoothly as stock or do you expect it to be slightly rougher?

Its not going to be butter smooth,as a matter of fact it will be a touch rough,hell the stock pinions are kinda rough sometimes.
But it should smooth out some as it gets used.

[rock hard]

Originally Posted by asw27x

would a 11t bully pinion work??
http://store.rc4wd.com/Bully-11T-Pinion-Gear_p_92.html

Its hard,real hard to get thr 12t to work right,I suggest if your doing ot yourself,go with the 13t superbully pinion,and its still not a easy task.

[RickM]

I got a 12t trex done tonight. I have an extra for good measure as well as a 13t. I worked pretty hard to get the pinion to not be an issue. I also had to shim quite a bit on the diff/ring gear. It is pretty rough but as Paul said that is normal. It was actually supper smooth but I was not getting solid contact, and after getting everything back up and running I noticed it was slipping some. I then went back in and shimmed the diff some more and it ain't slipping but it is rough. I am hoping to get some good break in. I agree that the best material probably steel, but to be honest, after recently tearing up a ring gear I have decided I kindof want the pinion to go first now and hopefully save me the trouble of having to locate a pinion again.

[asw27x]

Originally Posted by rock hard

Its hard,real hard to get thr 12t to work right,I suggest if your doing ot yourself,go with the 13t superbully pinion,and its still not a easy task.

like it would be to small or just hard to work with