My list of recommended upgrades and modification for the Redcat Racing Ground Pounder ( part 2)

To continue on my recommended upgrade and modification list .

I figure the next area I want to focus on is the front and rear axles .

All over the internet you can read about people who have broke axle housings on the Ground Pounder but to be honest I feel most of the breakages could easily be avoided by making a few modifications .

Modification number 1:
Drill out all the screw holes in the axle halves so that 3 mm  screws will pass through with little to no resistance . Next install longer 3 mm screws that will allow a small diameter washer and a nut to be installed .

Reason's

The holes in the axles are small and require the screws to be threaded through both halves of the assembly .
Drilling out the holes speeds up assembly.
I also feel this clamps the axle halves better and increases the rigidity of the assembly and makes the halves act  more as one unit  .

Modification number 2:
Shimming the differential and ring and pinion is the next modification I would recommend . Shimming the ring and pinion gears is about give and take . I recommend adding shims to the side bearing of the differential till there is no side to side play . I then move shims from left to right and right to left till the pinion and ring gear mesh with just a tiny bit of play . Adding shims behind the pinion can move the pinion inward increase the contact area and the strength of the ring and pinion .  So moving the pinion inward is a good thing . The main cause of compromise in shimming is binding when the steering knuckles are turned as the dog bones are a couple millimeters 2 long for perfect differential placement  , at least in my experiences .  As a finishing touch I also shimmed the pinion on the outside so it can not move inward by putting a brass bushing between the bearing and the drive shaft yoke . I sanded the bushing to make it the right thickness .


Modification number 3:
Clean the Grease out of the differential  and fill them with silicon oil . Currently I'm  using 5000 wt hot bodies diff oil in the  rear and 3000 wt HB oil in the front . "I'm considering going to thicker diff fluid in the future"   Even using the 3000 wt and the 5000wt  oils I can say stability and drive ability have increased greatly due to the reduction in tire ballooning when weight shifts off a tire and for mud and snow it will keep you chugging forward with authority  .

My list of recommended upgrades and modification for the Redcat Racing Ground Pounder ( part 1)

In the time I have owned a Redcat Racing Ground Pounder I've broke a few things my list and my step fathers can be found here .  Link                 

The first thing you should look in to upgrading on the Ground Pounder is the motor : 

Really I find the top speed pretty good but I feel the truck needs more torque for driving in grass and driving off road . 

My  recommendation  is a 550 motor with 19-22 turns here are a few examples :

Redcat Racing Part # 28446  sells for about $16.99

Traxxas Titan  (21T) Part # 3975 sells for about $21.49 

Thunder Tiger  part # PD9221 sells for about $27.99

My second upgrade I recommend is to upgrade pinion and spur gear . 

Part # bs801-014 is a 43 tooth mod 1 spur gear made from a composite plastic that can replace the stock spur .
About $10.00

Part # MPO-017 is a steel version of the BS801-014
About  $14.00







Now you will need at least 1 pinion that has a Module 1 tooth profile . If you are using a motor with a 1/8th inch shaft " like the ones listed above " here are a few options.

Pinion Gear, 9T/12T x 3mm, Mod 1 part # ECX232028 

about $13.00 for a pair 

OFNA 3mm Bore Mod 1 Pinion Gear  about $12.00 each  

11 tooth = Part # 21316

12 tooth = Part # 21314

13 tooth = Part # 21315

14 tooth  = Part # 21306

15 tooth = Part # 21311

16 tooth = Part # 21312

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 .