Dedicated Throttle & Brake Servos (?)

[Erik Beeman]

Hello,

I'm reaching out because I'm currently building a replica RC truck modeled after my drift truck. This is powered by a 70cc chainsaw engine, chain driven RC car I've built & machined from scratch. I'm looking for a little bit of input on servo setup and transmitter recommendations.

The sole purpose of the RC truck is to drift just like it's full size counterpart. It's approximately 1/4 scale and is about 70lbs. The project is not completed just yet. What I need to do is get the electronics sorted out. I need the throttle to be it's own servo, and I want to have a "hand brake" for the rear axle so I can lock up the rear. I'm undecided on hydraulic or cable operated, but have already built a disc brake setup for the live rear axle.

A few years back a built another drift car, a 350Z, and I used a single servo for the brake and throttle, but that was set up a little different and I wasn't a huge fan of how it performed. It was also pretty complex mechanically, and I'm hoping I can design something more simplistic this time around.

I plan on using a pistol style transmitter, but beyond that, I don't know what I'm looking for. My questions are:

• How do I run a servo for the throttle and brake, separately? I still want to use the trigger for both throttle and brake, just like a throttle/brake servo setup normally is, but I need there to be two separate servos. Is this a wiring thing, a receiver thing, or a programming thing within the transmitter? Or a little bit of all three? This is probably my most important question to learn.
• How many channels will I need to run this setup?
• Are there any recommendations for a good transmitter/receiver package? My budget for the transmitter/receiver is hopefully around $80-$100USD.

I appreciate the time and feedback. Thanks!

Regards,

Erik

 

[Seandonato73]

I'll expand later on my thoughts. But for now you better up your budget by at least $500.00. And unless you have a clutch disconnect your going to have to come off throttle for the rear to lock up and start the kinetic friction needed for the drift to start. Your clutch will stay engaged and fight the brakes other wise.

 

[Erik Beeman]

Hi Seandonato,

Thank you for the reply. I do anticipate that when I press the trigger forward to engage the brake, it will inherently drop the throttle. This is by nature and design and is actually what I want. On my previous car, I had built the same set up and it worked pretty well. If I was attempting to stay full throttle, I don't think it would work without a neutral.

When you reference the cost, can you expand on your comment? Are you implying that in order to run dual servos, I need a transmitter that is in the $600 range? I can't argue that point, as I'm not familiar enough (hence my original questions), but I do find that hard to believe. I'd love to learn more. How does a multiple-servo design like that work? Thanks

Regards,

Erik

 

[Milo]

I’m about to build a Baja with a 3 servo setup. I’ve got a Bonesteer kit that needs separate throttle and brake servos and to complicate matters I’m putting Mecatech front brakes on it as well.

So I’ll have a steering servo, one for the rear brakes and one for the throttle and front brakes.

I’ll be running the throttle and both brakes from 1 channel.

Fcuking servos cost a small fortune I spent about the equivalent of $400. FFS.

 

[Erik Beeman]

I’m about to build a Baja with a 3 servo setup. I’ve got a Bonesteer kit that needs separate throttle and brake servos and to complicate matters I’m putting Mecatech front brakes on it as well.

So I’ll have a steering servo, one for the rear brakes and one for the throttle and front brakes.

I’ll be running the throttle and both brakes from 1 channel.

Fcuking servos cost a small fortune I spent about the equivalent of $400. FFS.

Hi Milo,

So, aside from the cost of the servos, how exactly does that three servo setup work? How is it done?

Regards,

Erik

 

[Milo]

Hi Erik,

I’ll need to know more about your setup as I’m not familiar at all.

I’ll use a Y-lead to connect the brake and throttle servos together then plug them into a single channel on the receiver. They will both operate at the same time.

I’m guessing you’ll need slide connectors on one or both of linkages, but it depends on your setup.

Cheers,

Milo.

Hi Erik,

I’ll need to know more about your setup as I’m not familiar at all.

I’ll use a Y-lead to connect the brake and throttle servos together then plug them into a single channel on the receiver. They will both operate at the same time.

I’m guessing you’ll need slide connectors on one or both of linkages, but it depends on your setup.

Cheers,

Milo.

By slide connectors I’m referring to the bit that allows you apply the brakes without yanking on the throttle in closed position.

Are you familiar with any petrol powered 1/5th scales?

 

[A Dawg]

Currently I’m running my 5ive as a brushless conversion and I’m also using the mechanical brake. Essentially the same thing. Throttle sends signal to the esc which would be the carb for you And when the brake is applied it opperates the manual brake servo. I’m using a futaba 3pv remote and you need to use a 4 channel receiver. If you use the 3rd channel you are stuck using the button on the side(which is better for a handbrake) but if you plug the servo into channel 4 you can channel mix and use channel 2 for throttle and 4 for brake all controlled by the finger trigger.

You might wanna use the 3rd channel and the side button for e brake. Look up the arrma infraction v2, it comes with a hand brake factory.

Im not expert but that’s what I did

 

[Milo]

Currently I’m running my 5ive as a brushless conversion and I’m also using the mechanical brake. Essentially the same thing. Throttle sends signal to the esc which would be the carb for you And when the brake is applied it opperates the manual brake servo. I’m using a futaba 3pv remote and you need to use a 4 channel receiver. If you use the 3rd channel you are stuck using the button on the side(which is better for a handbrake) but if you plug the servo into channel 4 you can channel mix and use channel 2 for throttle and 4 for brake all controlled by the finger trigger.

You might wanna use the 3rd channel and the side button for e brake. Look up the arrma infraction v2, it comes with a hand brake factory.

Im not expert but that’s what I did

That sounds a bit pants having to use a separate button for brakes. I wouldn’t recommend that. If you do that, I suggest you don’t run it near any obstacles and master your coordination.

Also remember you’ll need a spare channel for a kill switch always.

 

[Erik Beeman]

Hi Erik,

I’ll need to know more about your setup as I’m not familiar at all.

I’ll use a Y-lead to connect the brake and throttle servos together then plug them into a single channel on the receiver. They will both operate at the same time.

I’m guessing you’ll need slide connectors on one or both of linkages, but it depends on your setup.

Cheers,

Milo.

By slide connectors I’m referring to the bit that allows you apply the brakes without yanking on the throttle in closed position.

Are you familiar with any petrol powered 1/5th scales?

Hi Milo,

I do have some 1/8 nitro trucks, but no 1/5 scale stuff. I've studied some 1/5 scale buggies/trucks as inspirations for parts of my design, but I can't say I'm 100% familiar with slide connectors.

On my previous custom build, I ended up designing a cam type horn for the throttle/brake servo. When the throttle was applied, it would, well, engage the throttle, but when I applied the brakes, and the cam spun backwards, there was a slot for the throttle linkage to loosely be, so as not to engage the throttle when the brakes were on. It was a tricky part and design to make, and I think I can come up with something better. But given the weight of my current build, and my intentions, I feel that two seperate servos would be best to accomplish my goal. However, if I'm talking about $400-600 in parts, I'm going to have to scrap that idea and focus on an improved design from my previous build.

I'm familiar with the Y design for dual servos, but I don't think it would work well in my application. I may use a dual servo for the steering though, but that is a whole different ball game for me right now.

Thanks for the input!

Regards,

Erik

 

[Milo]

Hi Milo,

I do have some 1/8 nitro trucks, but no 1/5 scale stuff. I've studied some 1/5 scale buggies/trucks as inspirations for parts of my design, but I can't say I'm 100% familiar with slide connectors.

On my previous custom build, I ended up designing a cam type horn for the throttle/brake servo. When the throttle was applied, it would, well, engage the throttle, but when I applied the brakes, and the cam spun backwards, there was a slot for the throttle linkage to loosely be, so as not to engage the throttle when the brakes were on. It was a tricky part and design to make, and I think I can come up with something better. But given the weight of my current build, and my intentions, I feel that two seperate servos would be best to accomplish my goal. However, if I'm talking about $400-600 in parts, I'm going to have to scrap that idea and focus on an improved design from my previous build.

I'm familiar with the Y design for dual servos, but I don't think it would work well in my application. I may use a dual servo for the steering though, but that is a whole different ball game for me right now.

Thanks for the input!

Regards,

Erik

If you post a picture of your setup we could probably advise you better.

 

[Erik Beeman]

I’m using a futaba 3pv remote and you need to use a 4 channel receiver. If you use the 3rd channel you are stuck using the button on the side(which is better for a handbrake) but if you plug the servo into channel 4 you can channel mix and use channel 2 for throttle and 4 for brake all controlled by the finger trigger

Hi A Dawg,

I think the bold text above is getting me on the right track, or at least the track I was thinking.
I just don't know what channel mixing is, to be honest. That's where I'm getting lost I think.

But if I could get a 4+ channel transmitter to accomplish my goals, I think I'm a step closer to figuring out something that could work?

Regards,

Erik

 

[Milo]

Hi A Dawg,

I think the bold text above is getting me on the right track, or at least the track I was thinking.
I just don't know what channel mixing is, to be honest. That's where I'm getting lost I think.

But if I could get a 4+ channel transmitter to accomplish my goals, I think I'm a step closer to figuring out something that could work?

Regards,

Erik

Download and read a Futaba radio manual. ??

 

[Erik Beeman]

Download and read a Futaba radio manual. ??

Hi Milo,

Awesome, even that little bit of information should help me quite a bit.
Not knowing brands or anything really left me blind. Starting somewhere is what I was looking for, thanks!

Regards,

Erik

 

[Rep732]

lets see the real drift truck. you have my attention as drifting is something i like doing as well

 

[Seandonato73]

For the size truck and the braking needs, duel servos will serve you better, amd you'll want dedicated channels for each. Steering is 1 channel, throttle and brakes will eat up 2 more, and an kill switch needs it's own channel. And that's assuming your not looking for front brakes as well, if so you would potentially need another channel for that as well. Like milo said, pictures would help with what were giving advice on. Your going to be in the $300.00 ish range for a radio at 4 channels for a futaba. I'd personally get the 7 channel that way you have spares for future use. At your current $100.00 mark your looking at a pretty cheap unreliable tx, and you still haven't gotten servos yet. They will net you around $100.00 each. Again not knowing how big this is, I'm basing using 1/5 scale servos, and not the smaller std size.

 

[A Dawg]

Yeah honestly I never done it before I just knew it was possible. I had to use the futaba manual as I went and set it up. People use the function to control front and rear brakes separate with just the finger trigger but be able to set front and rear bias with two different servos. And to be clear the button in the side would be for the ebrake only and the throttle trigger could be used for gas and normal brake. Like I said if you look up the the arrma infraction v2 if has gas and brake using the trigger and rear only (e brake) using the button. It’s a electric car but same purpose. Just control servos instead of esc. It’s actually much easier then using the finger trigger. Also if you use the finger trigger as the e brake then what happens when you need to stop quick. That way you could use the button as a e brake and Normal trigger finger for regular brakes. The button is where your thumb rests so you can push it without any hesitation.

 

[RcJunkie13]

Ok so I’m just thinking aloud here, so if you kept one servo for throttle and (regular) brake, then you can have another independent servo as a rear hand break. Think about the Baja front break setups, you can have something like that linked up to a seperate channel (activated by a switch in the radio), then you can lock up the rear wheels on command, to drift when needed, then you can have an independent hand brake.

 

[Milo]

Yeah honestly I never done it before I just knew it was possible. I had to use the futaba manual as I went and set it up. People use the function to control front and rear brakes separate with just the finger trigger but be able to set front and rear bias with two different servos. And to be clear the button in the side would be for the ebrake only and the throttle trigger could be used for gas and normal brake. Like I said if you look up the the arrma infraction v2 if has gas and brake using the trigger and rear only (e brake) using the button. It’s a electric car but same purpose. Just control servos instead of esc. It’s actually much easier then using the finger trigger. Also if you use the finger trigger as the e brake then what happens when you need to stop quick. That way you could use the button as a e brake and Normal trigger finger for regular brakes. The button is where your thumb rests so you can push it without any hesitation.

Dude, first of all the wall of words gets my goat.

You’re also talking out of your blow hole. Who the fcuk has a handbrake on their RC??? An E-brake as you call it only operates the rear wheels.

A drift machine will be either rear wheel or all wheel drive. When would you only want to operate the rear brakes only? This is an RC, not Ken Blocks Hoonigan.

A petrol, gas, benzine powered RC car does not need this and they are nothing like an ARRMA electric car. You are confusing the situation because Erik will definitely have mechanical linkages to all systems.

 

[Seandonato73]

You cant compare an e machine to gas powered. When you hit the e brake function the power to the motor is instantly stopped for a split second, thus starting your change from dynamic friction to kinetic friction. Same is done when you stab the clutch as you hitting the hand brake real world. The driving force must be stopped for that fraction of a second. We don't have a clutch pedal in rc, so you need to dump throttle wile applying full brake and get back on the throttle to keep the kinetic friction in motion.

Dude, first of all the wall of words gets my goat.

You’re also talking out of your blow hole. Who the fcuk has a handbrake on their RC??? An E-brake as you call it only operates the rear wheels.

A drift machine will be either rear wheel or all wheel drive. When would you only want to operate the rear brakes only? This is an RC, not Ken Blocks Hoonigan.

A petrol, gas, benzine powered RC car does not need this and they are nothing like an ARRMA electric car. You are confusing the situation because Erik will definitely have mechanical linkages to all systems.

Skip my wall of words then ?

 

[Milo]

You cant compare an e machine to gas powered. When you hit the e brake function the power to the motor is instantly stopped for a split second, thus starting your change from dynamic friction to kinetic friction. Same is done when you stab the clutch as you hitting the hand brake real world. The driving force must be stopped for that fraction of a second. We don't have a clutch pedal in rc, so you need to dump throttle wile applying full brake and get back on the throttle to keep the kinetic friction in motion.

Skip my wall of words then ?

You know what I mean Sean. ?
If you can play the piano like this Erik you’ll be fine having a separate brake button.