Why a 1/16 scale Traxxas transmission maybe good for your crawler .

So here is my reasoning .

 The 1/16 Traxxas transmission is a very small unit and is very compact .

 It has pretty much proven its self to be a strong and durable transmission as its quite common for people to buy a Traxxas 1/16th scale Revo or Summit and install 1/10th scale truck wheels and rubber and then install 540 or 550 brushless systems intended for 1/10th scale car's and trucks .

So what pushed me over the top and made it my must have transmission ? The gear ratio flexibility . The transmission is designed as a double gear reduction where the center gear(s) are not a idler like most transmissions in RC but acts as a jackshaft . Traxxas designed the transmission so that its ratio could be changed by swapping 2 gears shown in picture below circled in green .

The reason for this was because they have and are using  this transmission in several chassis configurations that use different size tires . So whats the transmissions ratios well you can choose 1.93 or 3.71 . OK so that doesn't tell you much . Here is a couple of examples showing the gearing extremes of this transmission vs a Axial AX10 transmission and the old Traxxas 272 magnum. the axle ratio listed is for a AX10 or HPI king axle and the motor is a generic kv rating for a 35 turn 3 pole 540 motor .    

Axial AX10 2.60	Traxxas 272 magnum	Traxxas 1/16 3.71 ratio	Traxxas 1/16 1.93 ratio
Low Differential Ratio: 2.92 Transmission Ratio: 2.6 Other Ratio: 1 Spur Tooth Count: 96 Pinion Tooth Count: 12 Total Voltage: 8.40 Motor KV: 1565 Tire Diameter (inches): 5. Top Speed (MPH): 3.22	Low  Differential Ratio: 2.92 Transmission Ratio: 2.72 Other Ratio: 1 Spur Tooth Count: 90 Pinion Tooth Count: 12 Total Voltage: 8.40 Motor KV: 1565 Tire Diameter (inches): 5. Top Speed (MPH): 3.27	Low Differential Ratio: 2.92 Transmission Ratio: 3.71 Other Ratio: 1 Spur Tooth Count: 55 Pinion Tooth Count: 18 Total Voltage: 8.40 Motor KV: 1565 Tire Diameter (inches): 5. Top Speed (MPH): 5.9	low Differential Ratio: 2.92 Transmission Ratio: 1.96 Other Ratio: 1 Spur Tooth Count: 55 Pinion Tooth Count: 18 Total Voltage: 8.40 Motor KV: 1565 Tire Diameter (inches): 5. Top Speed (MPH): 11.17
High Differential Ratio: 2.92 Transmission Ratio: 2.6 Other Ratio: 1 Spur Tooth Count: 72 Pinion Tooth Count: 30 Total Voltage: 8.40 Motor KV: 1565 Tire Diameter (inches): 5. Top Speed (MPH): 10.72	High  Differential Ratio: 2.92 Transmission Ratio: 2.72 Other Ratio: 1 Spur Tooth Count: 76 Pinion Tooth Count: 31 Total Voltage: 8.40 Motor KV: 1565 Tire Diameter (inches): 5. Top Speed (MPH): 10.01	High Differential Ratio: 2.92 Transmission Ratio: 3.71 Other Ratio: 1 Spur Tooth Count: 45 Pinion Tooth Count: 31 Total Voltage: 8.40 Motor KV: 1565 Tire Diameter (inches): 5. Top Speed (MPH): 12.42	High Differential Ratio: 2.92 Transmission Ratio: 1.96 Other Ratio: 1 Spur Tooth Count: 45 Pinion Tooth Count: 31 Total Voltage: 8.40 Motor KV: 1565 Tire Diameter (inches): 5. Top Speed (MPH): 23.51

Now you probably wont use the 1.93 ratio in a crawler but the flexibility would be nice to have (could throw some touring car tires on and go cruising around the local carpet track at a brisk pace )

So whats the down side ?

 I think the main reason this hasn't found more use in crawlers and other projects comes down to the output shaft size . Its small with a diameter of  4 mm  its smaller than the shafts most drive shafts attach to . Most drive shafts used in crawling have a hole designed for a 5 mm  or 6 mm shaft .   Now the final drive gear that attaches and drives this shaft has a 5mm hole and the shaft its self is 5 mm in the center and is machined down to 4 mm at its ends . The shaft has been circled in the diagram above . By replacing the bearings with 8x5 bearings and replacing the shaft with one that is 5 mm from end to end common drive shafts should be able to be used . I am currently looking for a shaft that will be a drop in replacement but one should be able to be made fairly easily . 

Parts list monster /crawler / mega truck . ( subject to change as the build goes on .)

Parts list so far

HPI 1/10 Crawler King Battery Box, Waterproof Receiver Box & Servo Mount	Crawler Battery Tray	$0.99	Ordered: 1	$0.99
HPI 1/10 Crawler King Front & Rear Axle Hub Carriers & 8 Bearings	Crawler Axle Carriers	$6.49	Ordered: 1	$6.49
HPI 1/10 Crawler King Complete Front or Rear Differential & Bearings	Crawler Differential	$10.99	Ordered: 2	$21.98
HPI 1/12 Wheely King Front & Rear Drive Shafts & Axles	Wheely Drive Shafts	$11.99	Ordered: 1	$11.99
Traxxas 1/16 Mini Slash Transmission & Spur Gear	mSlash Transmission	$13.99	Ordered: 1	$13.99
HPI 10 Bullet MT / ST Flux Front & Rear Assembled Shocks & Springs with Oil	eBullet Shocks	$8.49	Ordered: 1	$8.49
Traxxas 1/10 Telluride 4x4 Drive Shafts, Wheel Hubs & Nuts	Telluride D/S	$18.99	Ordered: 1	$18.99
Traxxas 1/10 T-Maxx 2.5 Turnbuckles, Servo Saver & Bell Crank	Classic Turnbuckles	$5.49	Ordered: 2	$10.98

So I got it in my head to build a low cost monster /crawler .

Deciding I wanted to build some thing with solid axles was the easy part . I'm a cheap person and to to be honest I wanted this project to be as cheap as possible . Mostly because I wanted this to be a trail truck / crawler and I had the feeling that it wouldn't take long for it to turn in to a smallish monster truck or something similar to a mega truck .


I'm gonna have a post dedicated to the parts that I am using for this project and a link will and can be found here . Parts list   after it gets posted . The parts I'm starting with  where purchased from https://www.dollarhobbyz.com and more sources will be added in time as there will be lots of little bits I'm sure I haven't even thought about and I'll probably be adding pieces I will be making my self .

The stars of the low budget show .

A pair of HPI Crawler king / Wheely king axles .

 At $40.45  through Dollar Hobbyz Plus shipping and handling and a little assembly these were the cheapest axles I could find . Given that Most of the Axial based axles seem to be selling for $40.00 per axle These seemed to be the best way to go .



How about a Traxxas 1/16th scale transmission with the 540 motor mount .

At $13.99 for this transmission from Dollar Hobbyz Its a steal and I think it may be a very over looked but great crawler transmission with just a bit of work . My reasoning may take a bit of explaining so expect a link here LINK to a post just talking about this transmission and the reasons why i plan to use it .

( 2 year plus update) Turnigy 4000mAh 2S 30C hardcase pack

Original post ( May 17, 2013 )
Well in the time I have owned 2 of these packs " a little over 2 years"  I have repeatedly compared it to the ZIPPY Flightmax 4000mAh 2S1P 25C Car Lipoly which is one of the cheapest hard-case packs on the market . To be fair they have both aged about the same. Both originally had usable capacities of around 4000 Mah and both are running around 2200 Mah these days when ran in my ZD Racing ZMT 10 and in less demanding applications "crawler and slower vintage cars and trucks " I see usable capacities around 3500 Mah. I will say these packs seem to require being balanced more often than the 4000 Mah zippy packs .  I also had a physical failure   recently . It seems the positive lead broke the tab that is used to attach it to the cell and so the pack is dead as I'm not going to even attempt fixing it . I do think this could have been prevented if I had forced some silicone sealant into the case around the wires to give them additional support .   But in short I feel I got lots of good use and bang for my buck with these packs and if you can't run the 4000 Mah Zippy packs due to your chassis design I feel Turnigy should be the next pack to check out .