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TXT-2 Agrios - MadInventor Gearbox Conversion

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MadInventor made this fantastic bespoke gearbox for his TXT-1 - http://www.tamiyaclub.com/forum/index.php?showtopic=73621#entry546981 - it just so happens he made another one and I found myself buying it last week...!

First of all apologies for the bad phone pics - I am no photographer...!

Took me a week to get around to trying to fit it but last night thought I would give it a go :)

It really is a beautifully made piece of kit - and lighter than I was expecting too.

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Rotates so smoothly too - all I did was add some Tamiya ceramic grease to the gears.

Truck all ready for surgery! :)

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Standard view of the underside...

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It only takes the removal of the battery and electronics trays and 4 screws to remove the gearbox - well, apart from the driveshafts.

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4.5 turns of lunacy! :)

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Installed in the new gearbox with a 14t pinion (was using a 15t in the old gearbox but ESC and LiPo were getting a bit warm..!)

Question for Martin - I could not fathom out the point of the supplied adaptor when it fits perfectly without it??!

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Another upgrade at the same time was to swap the pathetic Tamiya driveshafts for Traxxas Revo ones.... All that is required is to swap the axles parts for UJ parts....

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Empty chassis awaiting its new heart...

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Bottom plate in - fits like it was factory made! 8)

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Gearbox about to be bolted down... after removing one of the cross braces that I guess doesn't exist on the TXT-1?

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Heavily shortened Traxxas driveshaft installed...

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and thats where I am up to for now - was up until midnight but was just too tired to finish it off! Will finish it hopefully this evening and test it tomorrow - might even shoot for a video...!

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Yes video please, would love to see how mental this thing is on a 4.5!

Are we sure Tamiyas gears are up to the task of Martins machine work? :lol:

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Hi Craig,

I'm so pleased the gearbox went in without a hitch.

To answer your question, the adapter plate is simply a spacer, as I was not sure what the length of the motor shaft would be. If you look at my original thread I had a longer shaft on the 4274 motor, and fitted the motor pinion backwards to the way you have fitted yours. As I didn't have any other motors to test fit with other than silver cans, I chucked in the spacer as a 'Just in case'.

I also had to remove the cross member out of my TXT-1 chassis but I don't think it's an issue, the steel underguard provides strong bracing at the bottom of the chassis.

Before you run it, it might be worth poking the 2 idler shafts with a pencil from the outside of the case to make sure they cannot slide out easily. If they will move, I would just put a bit of aluminium tape over each end, or maybe a dab of silicon sealer on them just to stop them working their way out.

I'm looking forward to see how this goes, it will be interesting to see if there is any grease left on the gears after the first run.... ;)

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Quick video - apologies for the rotation as I had to prop my phone up (in hindsight I should have had the phone landscape!) - my 4 year old isnt up to camera work yet

Still - you get the idea :)

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How does that compare to your "big" motor Martin? I like the idea of more torque - although as this motor cost me the princely sum of £5 I might as well wear that out first :)

I just love wheelying it to be honest lol 8)

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Great craftmanship in the making of that gearbox.

Are those traxxas shafts realy stronger than stock Tamiya prop shafts?

I only ask as I have twisted those traxxas shafts, running in an Emaxx

4.5 in a txt??? you are a brave man

I would keep an eye on the axles, they are not designed for that power

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How does that compare to your "big" motor Martin? I like the idea of more torque - although as this motor cost me the princely sum of £5 I might as well wear that out first :)

I just love wheelying it to be honest lol 8)

Definetly a lot faster than mine (and I'm running mine on 3S). My motor is only 2000KV though, isn't 4.5T around 6000KV ?. Even if I ran mine on 4S I'd still only be getting about 3/4 of the RPM of yours on 2S, but I think my motor would be better for towing ;)

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This one is 7800kv hence my desire for a smaller pinion - the lipo was warm after this run...! Its only a cheap 30c one though...

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Great craftmanship in the making of that gearbox.

Are those traxxas shafts realy stronger than stock Tamiya prop shafts?

I only ask as I have twisted those traxxas shafts, running in an Emaxx

4.5 in a txt??? you are a brave man

I would keep an eye on the axles, they are not designed for that power

I've not broken or twisted a Revo shaft yet, and I'm running them in both my TXT and my Grapple skidder (Which has a model ship brushless motor in it :), and I used that to drag a 6ft 4 inch square fence post with). I managed to chew up standard Tamiya TXT shaft with a couple of silver cans running and 8.4V battery in my TXT when I first had it. The problem with the Tamiya shafts is that they are made of brass and so is the larger of the 2 UJ pins, so the slightest bit of wear, the pin get mis-shapen, and then they eat themselves.

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This one is 7800kv hence my desire for a smaller pinion - the lipo was warm after this run...! Its only a cheap 30c one though...

:o That's a lot of KV :o

If you want to make it easier to wheelie, have you thought about putting the gearbox in backwards so that the motor is under the battery box. I know you can't do it with the standard gearbox, but the custom one has the motor mounted lower, and the smaller the pinion you use the lower the motor gets.

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With too many rcs to play with it only comes out now and again to scare myself :-)

Yes I was tempted to do that when I put the gearbox in - might try it when I refit it this time...

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2000kv on 4s, those shafts will hold up to that much power all day long

try it on 6s :rolleyes: and I promise you those plastic traxxas shafts do fail

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What Skip has been tactful / considerate enough to keep out of this thread so far is that the bottom shaft of the gearbox failed on the first run. Where I had secured the drive hex to the drive shaft with Loctite 638, the Loctite failed.

So what I have done to remedy this is to make a new final drive shaft for him:

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The drive shaft at the top of the picture is the original design (which came out of my gearbox), and the lower one is the new drive shaft.

On the original design, only the portion of the shaft which had the hex on it was attached with Loctite, the other sleeve was just there to act as a spacer.
The new design is all one piece, which gives far greater surface area for the Loctite to grab on, and as a belt and braces measure, I've also fitted 2 5mm grub screws to it as well. I machined 2 flats on the drive shaft to accept the grub screws, and filed out the corners to remove any corners which might provide points for a crack to start. I also keyed the inner shaft with a needle file (That's the rough surface finish in the pic below) and then cleaned it with alcohol thinners before assembling with the Loctite this time.

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Hopefully this will be good for the 7800KW KV this time.

To quote a famous pilot 'Hold together baby, hold together' ;)

I'll be making another for my own gearbox as well when I get a few hours free as it's a better design.

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Looks fantastic Martin - thank you very much for your efforts in resolving the issue - rest assured it will get a good testing :D

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Nuts.

I love it.

I can't do this to my TXT though, I have a Mad Force for wheelie good fun lol

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Bit late updating the thread but I fitted Martins upgraded shaft to the truck on Friday evening and gave it a good test on Saturday. It performed perfectly - a whole battery went through it with no issues at all - love it! :)

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