Pinions And Spurs

So finally got around to building my next rc car. This time around I was looking for a good RTR chassis that was 4wd and economically priced. The HPI Sprint 2 seems to have fit the bill for being under 200.00 for a complete RTR package. I did however replace the radio equipment and used my spektrum dx3r system, everything else is bone stock.

The car handles well with it’s stock x-pattern d compund tires, I would guestimate the top speed to be around  20-25mph with the 15t firebolt brushed motor. The steering seems a little loose and I would suspect that the chassis would probably not handle a faster motor than a 5700kv type without upgrading some key components.

I plan to do a video on performance of the stock setup followed by a brushless conversion and then another look at how the chassis handles more power.

Also note that since this is brushed, the power is not used efficiently so run-times are low.. around 5 minutes or so.

Thought I would share some new tires I have started using that can mounted on scale wheels, and at the same time dont sacrifice performance.

HPI Pro Compound V-Grooved (Wet/Rain/Dry Tire)
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXM992&P=7

HPI Pro Compound X-Pattern (Wet/Rain/Dry Tire)
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXM979&P=ML

HPI Pro Compound Racing Slick (Dry Conditions)
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXM972&P=7

The above list is something recently I have started to look at will post more as I find more that are all easily available, high performance ( race quality) and are reasonably priced.

This is a short video of the recent run I did on this car, I have to admit this is one Tamiya chassis that I am least impressed with.

It is definitly more adjustable from the TT01E but if you are thinking about upgrading I would say just go for the Ta05 or better. The car does not seem to handle brushless systems too well, the fastest motor you can use in my experience is the super stock from Tamiya anything more you will start to rip the car apart or just keep burning through spur gears.

So finally got around to test out the new motor/gear/25c lipo setup on the TC5r. It was an extremely hot day, average ambient temperature was about 90-96. The car performed well, but ended up blowing the left rear tire and crashing as a result

The Mamba Max 5700 combo 87/22 gearing with Trakpower 3s 4900 25c combo is very very good, I enjoyed running the car. However the FPV equipment it self is pretty heavy along with the 3s lipo made the car somewhat unstable at high speeds, I estimate the car was topping out at around 60mph I did not get a chance to use the radar gun to make sure but given the setup and my calculations it should be doing at least that much.

I intend to get an OSD setup soon and perhaps in time upgrade to a 5.8ghz video system so I get better reception, the whole project has been challening because there are a lot of moving parts. The video gear and the car the electrics all need to be setup well and mounted on the car so they dont make the vehicle unstable.

I think I’ll be doing this in phases, next one will definitly be the OSD so we can start seeing some data like motor temperature, RPM and of course GPS based speed.

My digital camera seems to have come back from the dead some how, so thought I would write a post on what I have been up to. 

I am currently working on selecting the best motor/esc/lipo setup for fastest 3s lipo race able car, so far I have tried the good old Novak 3.5R, the Mamba 7700kv and Traxxas 3500kv motor. 

All three motors were run on the TC5R  chassis using the VXL3S speed control, they all survived the 11.1v of power mostly because they probably were never able to exceed their rpm limits and perhaps with a lot of luck as well.

The problem is that the lower turn motors like the speed passion 2.5R run very very fast on 2s but seem to max out at or around 60mph. That is plenty fast for racing, but I just have the itch to see if we can go faster, maybe around 70-80 clean on top speed and still be reasonably racable.

The TC5R with the above motors sits pretty heavy and I have had to use harder roll-bars so it does not hit the ground everytime I make a fast corner. The over all stability seems better due  to added weight but I still need a solid motor/gear combo that can give me over 60mph and be able to go around a large track without too many issues.

My plan was to order the Mamba Max 5700 system which I have installed and done some inital testing, everything looks good just hope the weather is clear this weekend so I can do some good test. Also this time around I plan to be in FPV mode, essentially a wireless camera mounted on the car so I can get a feel of the car and power as if I was actually sitting in it.

Folks I have been out of commission lately due to broken camera, I have not been able to take video or still photos of anything so far.

Currently I am working on two projects, one finding and building the fastest 2s lipo race able rc car and I think I am almost concluding that project. Secondly, working on building the fastest 3s/4s brushless race able 1/10 setup, this one is taking up most of the time at the moment.

The fastest 2s so far is the Tamiya TA05 with mamba max and speed passion 2.5R, the car has  been running amazingly with top end speed of about 60mph and totally controllable on a large track. The problem however is that even a 5400mah or 4900mah lipo pack runs out within 5 or so large track laps, I am looking for perhaps an 8000mah or maybe even a 10000mah pack to see if everything  balances out, however at that point the question would become to effectively cool the motor so it keeps running efficiently, the mamba max is at around 120-130 at the end of a full pack so at this point not too worried about it.. but the motor tends to be 140-160

The 3s/4s setup is a bit dicy right now, I am using the TC5R as the chassis but can’t seem to find a good motor/gear/esc combination that can give reasonable run-time along with making the car as fast as possible. So far I am still running the VXL 3S as the esc but have tried Novak GTB 3.5R motor, Mamba Max 7700kv motor and the VXL 3500kv with mixed results.

The Novak GTB 3.5R obviously is unable to run more than 5 minutes with 3s, shuts down with over-heat and does not seem to hit it’s top end. The 7700kv does however seem to perform a lot better and longer run-time but lacks the torque that I need with added weight on the car so not really breaking the 50-60 mph  barrier. The 3500kv motor seems very solid but I think it’s asking for 4s to get it going properly, so will have to see what happens.

I have ordered the mamba max esc, 5700kv mamba motor and the CC BEC. I will start experimenting with 4s setup on VXL 3500KV motor and surprisingly enough the folks at speed passion that their 3.5R 540 can is able to do 3S … I was really surprised but I have become a big fan of their electronics so will have to see that as well.

As soon as I get my camera equipment going again will start post pics and videos of my findings, stay tuned.

Since my Novak GTB 3.5 has blown up most likely due to gearing issues, I decided to upgrade the TA05 and TC5R to break my current 53mph record with Novak GTB and TC5R combination setup. So the first test was to run the TA05,  it was a very windy day and I was also experimenting with HPI X-pattern wheel/tires on both cars so was not able to get my target 60mph top speed. 

According to my calculations tha TA05 should have hit approximately 60mph, however clocked a clean 50mph (previous top speed 43mph) run using a Speed Passion 2.5R motor. This is a fantastic motor, not only does it have plenty of torque (using Trakpower 2S 5400mah 16c lipo) but an outstanding 13800 rpm/volt and it sounds awsome.  I think if it was not as windy and I was not using the rear wing, I reckon I should have hit close to 60 but that will have to wait since I am waiting to receive a Trakpower 2s 4900 25C lipo pack.

The 4900mah 25C rating should give me 4.9 x 25 = 122.5 amps, currently with the 5400mah 16c I am getting 5.4 x 16 = 86.4 amps. The Mamba Max ESC is rated 100amps max so with the 4900 25c pack I should definitly get more torque and hopefully my target 60mph top speed.

In all I am very happy with the overall performance, the motor is very light and the TA05 with everything weighs only 1472grams. I think once I get the 25c rated lipo, I will do another speed run to try for 60mph again, hopefully it’s not too windy again.

The TC5R I decided to turn to a traxxas VXL 3S system that I had bought a while back, but never really used it much. The reason behind using this system was essentially research on the internet and realizing that I will need much more torque i.e. battery power to hit traget speeds of 70-80mph. And boy does this thing have some serious power, the motor is 3500kv and I am running 48p 75/35, since this is a low kv motor I am able to use trakpower 3s 5400 16c lipo.The car is definitly heavier but that is increasing general stability and straight running, the torque on this thing is so nice the car continous to wheel spin even when reaching higher speeds. The problem however during this run is that I was unable to do enough runs to actually clock the speed by my bushnell radar gun. 

In only a two test runs I lost traction big time and the car flew about 4-5 feet in the air after hitting the grass. Fortunately there was no major damage, I lost the right rear suspension holder and the spur gear (kimborough spur) seems to have disintegrated, not sure if this was caused due to heat or simply got crushed due to too much power.

This is my first rc motorcycle, have to admit it is a lot of fun and comes as an RTR kit. The thing I was most impressed about it is the fiber glass chassis, the radio equipment is impressive as well but if you are a already into cars or anything else you will definitly want to use a 2.4ghz system like spektrum dx3r.

I think the goal for Venom’s kit is to get people invovled in the hobby which is why I think they have such an incredible price on an RTR version. Please know that it is nothing like driving an rc car, you definitly have to be more alert and manage corners and throttle differently, so if you are curious about RC motorcycles definitly go for the kit.

As for me I did get the kit liked it a lot and decided to go full on in learning more about motorcycle dynamics and finally upgrade some aspects because I did crash a whole lot. The following are some very basic things that I think one should consider upgrading to get more out of the GPV-1

1. A good brushless system, I chose the Novak Mongoose 10.5
2. You will need 0.5 mod pinion gear from Novak ( 15t is the smallest that will fit)
3. Alloy steering stem if you anticipate on having multiple head on crashes
4. A good battery pack, lipo is preferred for sure
5. The Mongoose ESC mounts best to the right side of the bike as shown above
6. The stock v5 tires seems to handle better for me on most surfaces, I have tried the v1 soft tires with minimum sucess
7. I am using the blue 17lbs springs from tc5r seems to get better handling than the stock 
8. Using velcro strap to mount the top part of the body because I thought it mounted better than the stock mounts and also the stock mounts break too easily due to weight of the rider on the bike and impact during crash

I think that should do it, as for any other modification. It goes without saying sky is the limit, just like other hobby grade kits Venom offers a wide variety of hop ups. The above I feel are the bare essentials, anything more is entirely up to the person and their riding style.

So finally got around to doing some speed runs!!! unfortunately the weather was still pretty bad. But it’s not all bad news, I got to test the car in the wet. I have to say the TA05 and Mamba Max combination is very good for the price.

The car handled really well and I was able to  squeeze in about 43mph on one of the runs. (I am using a radar gun). The small puddles of water were slowing me down a bit but over all it was a lot fun to run the car.

This is the same Ta05 that I have in part I and II, Ta05 with Mamba Max 7700kv, robinson racing 48p 75t spur and 22t pinion. I estimated the top speed to be 46.5mph so getting 43mph was not bad at all.

Finally got around to making some more changes and taking videos etc.. the two main updates are adding anti-roll bars and some scale looking air ducts. I have also removed the front bumper because I am getting ready to some speed run testing next week, I have also removed the rear spoiler in order to make sure I get minimum amount of air resistance.. but that’s next week hopefully the weather is better

These are the two yellow wire type things one for the front and the other for the rear of the car, these help to keep the car steady when making very fast corners

I need to get a better camera at some point, this one’s good but does not have a good enough resolution