brushless 1/5 4wd conversion about to begin! couple questions.

[Unsullied_Spy]

Originally Posted by aqwut

I think I emailed castle last year about using the Hydra's in a Land vehicle.. they said it wasn't a good Idea, if I can remember...

They also say not to run the MM past 3s

There are people successfully running Hydras in cars and trucks, the biggest issue is heat dissipation but if you're running a 240 amp ESC and drawing half that you should be able to get some decent run time out of it before letting it cool. If you feel like voiding the warranty even further you could modify the ESC to take heatsinks, but you would probably need some kind of thin heatpipe cooler in this application.

[Ryu James]

Originally Posted by lincpimp

If you run 10-12s and are not trying to gear too high I am sure the hv180 will work. Up at 10 and 12s pulling more than 100amps is making some serious power. I used a 60amp esc on 8s in a savage and had no issues, so triple that rating with higher voltage in a 15th scale should not pose a problem.

RJ, can you weight the chassis without the motor or batteries as it sits with the tires on? Just wondering what it will weigh with my proposed setup, and I know the weights of all of the individual components.

yes. i have a nice little digital scale i picked up a few weeks ago for weighing RC stuff. it will weigh up to 30lb i believe. as soon as i get back home i will post the weight of just the roller.

[Overdriven]

I had an FG monster truck awhile back in need of a steering servo. I too was concerned about the relatively low torque ratings of the 1/4 scale servos out there and picked up two 1/4 scale 200oz hitec's. Thankfully I tried using just one first and ended up returning the other as it turned the wheels like my 9100T did on my Revo. Also the 1/4 servos have stronger gear sets in them to take the higher shock loads a heavier truck will see. I was also powering the servo directly off the reciever battery instead of through the reciever, which alot of 1/5 guys do. It gives the servo some more power and insures the reciever doesn't burn out from the increased load placed on it.

Edit: Cool project man, I really dig the large scale stff, can't wait to see it finished with vids.

[Ryu James]

Originally Posted by Overdriven

I had an FG monster truck awhile back in need of a steering servo. I too was concerned about the relatively low torque ratings of the 1/4 scale servos out there and picked up two 1/4 scale 200oz hitec's. Thankfully I tried using just one first and ended up returning the other as it turned the wheels like my 9100T did on my Revo. Also the 1/4 servos have stronger gear sets in them to take the higher shock loads a heavier truck will see. I was also powering the servo directly off the reciever battery instead of through the reciever, which alot of 1/5 guys do. It gives the servo some more power and insures the reciever doesn't burn out from the increased load placed on it.

Edit: Cool project man, I really dig the large scale stff, can't wait to see it finished with vids.

so do you think i should go with a 1/4 scale servo then? i heard the JR HVT has huge teeth on the gears. the stock setup on this uses a 1/4 servo for the steering and a standard servo for the brake. i was just going to use standard for both. i did find these 1/4 servos. defintely the strongest i have found so far in the 1/4 size.

http://www3.towerhobbies.com/cgi-bin...&I=LL6955#tech

http://www3.towerhobbies.com/cgi-bin...XVPF0&P=8#tech



to linc:

i weighed the chassis as a BL roller and it weighs 19.3 pounds. that was with the battery trays on it. so here are the other stats, according to memory.


servo: 2.5oz each. x 2
2215 Neu: 25oz.
NeuEnergy 5s Lipo: 22.5oz x 2
Hydra 240HV ESC: 7.7oz



So all together i get a weight of roughly 24.5 pounds. I am gonna add on another 8 to 16 ounces for wire, screws, mech brakes, mounting hardware for esc, etc. so the finished product should weigh in at 25lb or just over.

This is the first build i have done where i havent tried to shed weight and been concerned with weight.

[_paralyzed_]

I can't wait to see this come together. Your builds are top notch.

[KaztheMinotaur]

The MT gasser with those HUGH tires weighed 37 pounds! I calculated hte impact force of it hitting something at 35 mph and it came out to around 400 pounds.

I'm currently using a scanner-rc.com servo for steering. 348 ounces at 6V. It is digital and works well for the price of $60. None of the US distributors carry that one so I have to get it from the Canadian distributor. $60 shipped to the US isin't bad though.

What about using this motor? http://www.innov8tivedesigns.com/pro...roducts_id=515 The power seems to be similiar or am I missing something?

if you still wanted a center diff,what about making a mount for the baja diff,then using an idler gear of some sort to get the pinion to it.it might also offer some more gear reduction if needed.just a thought...

[lincpimp]

Originally Posted by dethklok151

if you still wanted a center diff,what about making a mount for the baja diff,then using an idler gear of some sort to get the pinion to it.it might also offer some more gear reduction if needed.just a thought...

Just go one step further, and use the entire 5b tranny, make a motor mount, and attach the 1st gear in the the tranny to the motor shaft. Kinda like sikeston's direct drive emaxx tranny setup.

[Ryu James]

Originally Posted by KaztheMinotaur

The MT gasser with those HUGH tires weighed 37 pounds! I calculated hte impact force of it hitting something at 35 mph and it came out to around 400 pounds.

I'm currently using a scanner-rc.com servo for steering. 348 ounces at 6V. It is digital and works well for the price of $60. None of the US distributors carry that one so I have to get it from the Canadian distributor. $60 shipped to the US isin't bad though.

What about using this motor? http://www.innov8tivedesigns.com/pro...roducts_id=515 The power seems to be similiar or am I missing something?

that motor is more like the size of a Neu 1515 (14.8oz). i have seen those motors but have never heard of anyone using them. i think my buddies might use those for some budget planes they build.


hey,
does anyone know why this servo says to use NiCD packs only?

http://www3.towerhobbies.com/cgi-bin...XVPF0&P=8#tech

COMMENTS: Use with NiCD batteries only
A note on Coreless motors: Conventional servo motors have a steel
core armature wrapped with wire that spins inside the magnets. In
a Coreless design, the armature uses a thin wire mesh that forms a
cup that spins around the outside of the magnet eliminating the
heavy steel core. This design results in smoother operation and
faster response time.

[Overdriven]

It's says "NiCd only" because they don't want you to use alkalines, but they haven't kept up with the rimes to include NiMh and lipo etc.

Personally I'd run a 1/4 scale servo. The two you linked still have alot of torque and either should be plenty. Also I don't care how big the gears are, there's no way they can be as big as a 1/4 scales, it's physically impossible. And what about the gears in the JR is big, the teeth, dia, width? Usually what happens in standard servos is the gears get wider to increase the contact area of the gears making them stronger. Even though the standard has more torque than the 1/4 scale, the 1/4 has stronger gears so it can stand up to the shock loads that get past the servo saver.

[Ryu James]

Originally Posted by Overdriven

It's says "NiCd only" because they don't want you to use alkalines, but they haven't kept up with the rimes to include NiMh and lipo etc.

Personally I'd run a 1/4 scale servo. The two you linked still have alot of torque and either should be plenty. Also I don't care how big the gears are, there's no way they can be as big as a 1/4 scales, it's physically impossible. And what about the gears in the JR is big, the teeth, dia, width? Usually what happens in standard servos is the gears get wider to increase the contact area of the gears making them stronger. Even though the standard has more torque than the 1/4 scale, the 1/4 has stronger gears so it can stand up to the shock loads that get past the servo saver.

makes sense. thanks for the advice.

[Ryu James]

THE 8MM, MOD 1.5 pinions are avail on RCM now. i ordered a few for the conversion. also, i met with machinist to start on motor mount


http://www.rc-monster.com/proddetail...=rcmbajapinion

[KaztheMinotaur]

So I was thinking...you aren't going to be able to run mechanical brakes that way you have it now. The brake pads ride on 50024 and 50074 which is connected to the D gear on the outside of the gearplate 50011. You have all that removed in order to run a pinion / spur to the center diff...which seems like the best idea.



In this picture the upper gear mounting plate is turned around to face the side that the pipe is normally on.



I think you are going to have to rely on ESC brakes...

[Unsullied_Spy]

Brakes? We don't need no stinkin' brakes!

You bring up a good point. I wouldn't rely 100% on ESC braking when it comes to something with that much kinetic energy, not with modern ESCs at least. I'd set the brakes to 10-20% on the ESC and come up with some mechanical brakes that will work. Running brake discs at the center diff like it's supposed to be will interfere with your gearing options unless you go for some really puny brake discs. I think I'd go with brake discs on the diff input cups or even 4 wheel braking. It'll take some work to figure it all out, but this conversion is going to be worth it.

[brushlessboy16]

I say front disk brakes for a 5b.. not sure on the hex size but they sure do look sexy...