Hybrid RC Car?

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TurboChargedHonda

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I've had this idea for quite a while and did a little research into this. So basically what I was thinking would be to add an electric motor in addition to the nitro engine which will hopefully add more power to the car while making it more efficient, but I'm still largely undecided on the platform to base it on. I think the platform with the most potential for a parallel hybrid would be a T-Maxx since it has the most space (and some E-Maxx parts might work with some modification). I thought about doing it on a Revo or a Slayer, but there would have to be another gear between the pinion and spur gear for that to work, and it has significantly less chassis space. I could also try the Nitro Slash by adding drive from the electric motor to the front wheels, but steering and suspension geometry is a big issue to solve (using a slash 4x4 front end might work, but there's still the complications of chassis space and motor mounting). I also considered nitros from Losi and Kyosho, but they might be out of my budget and parts support doesn't seem as good as the Traxxas nitros. I could also get a cheap eBay/Amazon nitro to do this, but I want it to last, so I don't think that's a good option.

If I am going with the T-Maxx, I am also stuck between the Classic and 3.3. Things that I like about the Classic are that it's cheaper, has a smaller displacement engine (more potential to be more efficient), and has reverse. However, my concern is the weaker differentials. Would it become a durability issue with additional power from a 2800kv motor on 3s?

Also, if anyone's curious, here's an example of a successful parallel hybrid RC car: https://www.rccaraction.com/pro-line-assists-university-of-kansas-to-build-hybrid-rc-vehicle/
https://www.rccaraction.com/pro-line-assists-university-of-kansas-to-build-hybrid-rc-vehicle/
Screen Shot 2022-08-01 at 11.04.52 AM.png
 

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Wtf that’s a trip
 

Chubaka

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The 3.3 should be longer the the 2.5, emaxx parts should bolt right up as alot of parts are the same number, the width should be the same. I thought about having a ttuck set up for nitro or electric, having both installed but abandoned the idea.

If your running full on brushless, I can see the diff issue. A hybrid I see it lasting, but the potential to go out prematuely compared to a nitro only. If you feel this an issue and still want the 2.5, you can buy 3.3 diffs from a chop shop.

If you do the nitro slash, I would try to use a rustler 4x4 front end, but your front and rear ratios will need some math to match.
 

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The 3.3 should be longer the the 2.5, emaxx parts should bolt right up as alot of parts are the same number, the width should be the same. I thought about having a ttuck set up for nitro or electric, having both installed but abandoned the idea.

If your running full on brushless, I can see the diff issue. A hybrid I see it lasting, but the potential to go out prematuely compared to a nitro only. If you feel this an issue and still want the 2.5, you can buy 3.3 diffs from a chop shop.

If you do the nitro slash, I would try to use a rustler 4x4 front end, but your front and rear ratios will need some math to match.
I hate math I’m good at it just burns my brain 🧠
There is gear ratio app online you can use it’s actually pretty cool
I downloaded it just help with my ratio on builds it will tell you speed RPMs ect.
 

tudordewolf

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I've entertained the idea of hybrid nitro a few times. I think your best bet is to use the electric motor like a "first gear" to reach taller ratios with the nitro.

A smallish lipo/brushless combo paired with a nitro motor could deliver snappy acceleration while using the nitro for the majority of the high-RPM power drain.

Maybe the electric motor is there to help it accelerate from a standstill, and nitro motor is geared tall to give it a massive top speed.

Here's another thought, could the electric motor be used for regenerative braking, effectively recapturing energy produced by the nitro motor instead of wasting it with the disk brake? Kind of like a mini-KERS

Anyone, here's someone else's series-hybrid nitro crawler:
 

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I've entertained the idea of hybrid nitro a few times. I think your best bet is to use the electric motor like a "first gear" to reach taller ratios with the nitro.

A smallish lipo/brushless combo paired with a nitro motor could deliver snappy acceleration while using the nitro for the majority of the high-RPM power drain.

Maybe the electric motor is there to help it accelerate from a standstill, and nitro motor is geared tall to give it a massive top speed.

Here's another thought, could the electric motor be used for regenerative braking, effectively recapturing energy produced by the nitro motor instead of wasting it with the disk brake? Kind of like a mini-KERS

Anyone, here's someone else's series-hybrid nitro crawler:
I like that, will have the feel of a manual, theoretically. Cool video also. I've seen a guy do a nitro conversion on an scx10 with cooling, but never a hybrid.
 

TurboChargedHonda

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The 3.3 should be longer the the 2.5, emaxx parts should bolt right up as alot of parts are the same number, the width should be the same. I thought about having a ttuck set up for nitro or electric, having both installed but abandoned the idea.

If your running full on brushless, I can see the diff issue. A hybrid I see it lasting, but the potential to go out prematuely compared to a nitro only. If you feel this an issue and still want the 2.5, you can buy 3.3 diffs from a chop shop.

If you do the nitro slash, I would try to use a rustler 4x4 front end, but your front and rear ratios will need some math to match.
In that case, I think I'll go with the 3.3 since I'll probably end up swapping out the Phillips screws for hex screws too, and I don't mind having a bit more power. Thanks for the suggestions!

I've entertained the idea of hybrid nitro a few times. I think your best bet is to use the electric motor like a "first gear" to reach taller ratios with the nitro.

A smallish lipo/brushless combo paired with a nitro motor could deliver snappy acceleration while using the nitro for the majority of the high-RPM power drain.

Maybe the electric motor is there to help it accelerate from a standstill, and nitro motor is geared tall to give it a massive top speed.

Here's another thought, could the electric motor be used for regenerative braking, effectively recapturing energy produced by the nitro motor instead of wasting it with the disk brake? Kind of like a mini-KERS

Anyone, here's someone else's series-hybrid nitro crawler:
Yeah, that's similar to what I was thinking, using the torque from the electric motor for low-speed acceleration, and the high engine RPM for top speed (I think that's how real car hybrids work too). Regenerative braking seems like an interesting idea, I'll look into it.

That crawler is pretty cool!!! I'm probably not going to build something that complicated, but it's definitely interesting to think about!
 

TurboChargedHonda

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Also, I think with the electric motor, reverse can also work with the one-way transmission (engine won't stall since it has the one-way bearing right?).
 

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Also, I think with the electric motor, reverse can also work with the one-way transmission (engine won't stall since it has the one-way bearing right?).
Engine has a centrifugal clutch. Under the clutchbell as it revs, it grabs. The bell alone spinning wont grab.

Then the engine has a clutch the spur activates to grap the gears so to speak. From there is an rpm clutch to second gear, reverse uses a 3rd gear inside to spin tje correct way.

For a locked tranny, you probably need a forward only. This is more durable then the tranny with reverse I'm told.
 

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I've also had this idea for my T-Maxx 3.3, but there might be a way around it, instead of the pinion on the motor being locked on, we use a centrifugal clutch for the motor, only the motor engages when the nitro engine is at redline for improve speeds, then a servo will control how much power will be directed by a manual clutch on the nitro engine to prevent damage when the motor is engaged, might take some printing, but be cool to show off
 

tudordewolf

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Weird, I was just thinking about this after reading about the new hybrid corvette and considering a post.

Here's my thoughts:

The mechanical brake should be removed, and braking handled entirely by the electric motor, in a regenerative capacity - this would effectively turn the hybrid system into a KERS (kinetic energy recovery system), every time you brake you'd be recovering energy. I think this would be the coolest aspect of the whole thing and the most beneficial to performance; I'm betting it would increase runtime on a tank by at least 20-30%, possibly more.

A brushless system would be crucial to making this all work.

The electric motor could be mated directly to the transmission, no one-way bearings or clutches or anything like that (important since it would have to provide braking) - it won't harm anything as long as the ESC throttle and nitro throttle are tied together (same channel) and they redline at similar RPM's.

The electric motor would allow you to reverse the vehicle while the nitro engine idles undisturbed, as Turbochargedhonda thoerizes.

It could even be a 2-speed nitro, and the electric motor would still deliver power regardless of which gear was engaged because the clutch bell "ties" the gears together: if the electric motor were driving the first gear, when it shifts up, it would still contribute because the power would go from the electric motor into the first gear, into the clutch bell, and then back into the second gear.

The electric motor wouldn't be used to increase top end, but primarily for its low-end torque, (and also throughout the power band) with the KV matched to the nitro motor's max RPMS so it can "keep up". The motor should probably be "one scale down" and the nitro engine slightly small - what I mean is, for a 1/10th, you'd want a 1/16th scale brushless system and a .12 nitro.

I'm thinking a 2440-size motor on 3S, with a battery between 1000 and 1500mah, which also drives the receiver / servos through a BEC seperate from the ESC. This is so the ESC could be set with a conservative low-voltage cutoff, so that when the battery runs low, it stops using the motor for boost and only to brake, while still powering the RX and nitro throttle/steering - you could keep running as long as you kept topping up the nitro tank, provided the thresholds were set right- might take a bit of trial-and-error.
Maybe setting the drag brake to a low setting would ensure that the battery always had charge as long as the nitro engine were moving the car.

The battery might last longer than you'd expect at first, because when you brake, you'd be moving kinetic energy from both the electric motor and the nitro engine back into the battery, while only consuming it through the electric motor; that is, on an electric-only car, if you accelerate and brake, you've lost some amount of charge to inefficiency, but with a hybrid nitro, some amount of energy from the nitro fuel would be re-invested into the battery's charge when you brake.

The nitro engine's clutch would experience less wear because it would have less time slipping while the car accelerates, since the motor would help it take off as soon as you hit the gas.

You could run the car in an "electric only" mode if you don't start the nitro engine, which would also be kind of a handy "return to shore" function like on the old Traxxas boats if you ran out of gas or stalled the nitro engine.

I'm very inspired by this idea and may be posting a build thread soon...
 
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Lukedavis

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I'm going to build one of these with a spectrum 3300kv motor and 85amp ESC on 3s. its gonna be ballistic. I have all of the parts needed too.
 

Basher_around_town

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Weird, I was just thinking about this after reading about the new hybrid corvette and considering a post.

Here's my thoughts:

The mechanical brake should be removed, and braking handled entirely by the electric motor, in a regenerative capacity - this would effectively turn the hybrid system into a KERS (kinetic energy recovery system), every time you brake you'd be recovering energy. I think this would be the coolest aspect of the whole thing and the most beneficial to performance; I'm betting it would increase runtime on a tank by at least 20-30%, possibly more.

A brushless system would be crucial to making this all work.

The electric motor could be mated directly to the transmission, no one-way bearings or clutches or anything like that (important since it would have to provide braking) - it won't harm anything as long as the ESC throttle and nitro throttle are tied together (same channel) and they redline at similar RPM's.

The electric motor would allow you to reverse the vehicle while the nitro engine idles undisturbed, as Turbochargedhonda thoerizes.

It could even be a 2-speed nitro, and the electric motor would still deliver power regardless of which gear was engaged because the clutch bell "ties" the gears together: if the electric motor were driving the first gear, when it shifts up, it would still contribute because the power would go from the electric motor into the first gear, into the clutch bell, and then back into the second gear.

The electric motor wouldn't be used to increase top end, but primarily for its low-end torque, (and also throughout the power band) with the KV matched to the nitro motor's max RPMS so it can "keep up". The motor should probably be "one scale down" and the nitro engine slightly small - what I mean is, for a 1/10th, you'd want a 1/16th scale brushless system and a .12 nitro.

I'm thinking a 2440-size motor on 3S, with a battery between 1000 and 1500mah, which also drives the receiver / servos through a BEC seperate from the ESC. This is so the ESC could be set with a conservative low-voltage cutoff, so that when the battery runs low, it stops using the motor for boost and only to brake, while still powering the RX and nitro throttle/steering - you could keep running as long as you kept topping up the nitro tank, provided the thresholds were set right- might take a bit of trial-and-error.
Maybe setting the drag brake to a low setting would ensure that the battery always had charge as long as the nitro engine were moving the car.

The battery might last longer than you'd expect at first, because when you brake, you'd be moving kinetic energy from both the electric motor and the nitro engine back into the battery, while only consuming it through the electric motor; that is, on an electric-only car, if you accelerate and brake, you've lost some amount of charge to inefficiency, but with a hybrid nitro, some amount of energy from the nitro fuel would be re-invested into the battery's charge when you brake.

The nitro engine's clutch would experience less wear because it would have less time slipping while the car accelerates, since the motor would help it take off as soon as you hit the gas.

You could run the car in an "electric only" mode if you don't start the nitro engine, which would also be kind of a handy "return to shore" function like on the old Traxxas boats if you ran out of gas or stalled the nitro engine.

I'm very inspired by this idea and may be posting a build thread soon...
It's a tough job to do, but it's all a fantasy we all crave for the performance of a recovery motor like you say KERS. I've been dreaming about this for years
 

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What about using a Traxxas ez-start upgraded with a brushless motor to provide a power boost to the nitro engine? Can still be used for starting the nitro and when it’s running it could be setup to provide additional acceleration.
 

tudordewolf

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What about using a Traxxas ez-start upgraded with a brushless motor to provide a power boost to the nitro engine? Can still be used for starting the nitro and when it’s running it could be setup to provide additional acceleration.

I thought about that, the EZ-start's gearbox has a reduction of over 10:1 (just eyeballing the tooth counts from a picture, probably over 20:1); a brushless motor would have to spin in excess of 100,000 RPM to provide assistance in motion, assuming the clutch is engaging around 10k rpm.

I've got a car with onboard electric start via a very similar system called wolunstart, (short video here) which replaces the receiver battery with a 3S lipo and powers the servos through a BEC- it's very satisfying to press a button on the remote and hear the engine crank and come to life. I want to add a fuel cutoff, too, so I can both start and stop the engine without touching it. Then, head-tracking FPV and a nitrous system, so you can have an immersive VR experience driving your car around with start, stop, and boost.
 

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Wouldn't the nitrous system take too much space judging by the electric motor and all the fancy stuff the car will have in order to have all this power? Nitrous is fine as a stand-alone accessory for nitrous but we're talking about an ESC, Motor, Battery, The receiver battery going to another spot, and the throttle cables. Personally, I think nitrous is a bit excessive and for all the power we're getting out of the car, it's not worth the 100 bucks.
 

tudordewolf

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Wouldn't the nitrous system take too much space judging by the electric motor and all the fancy stuff the car will have in order to have all this power? Nitrous is fine as a stand-alone accessory for nitrous but we're talking about an ESC, Motor, Battery, The receiver battery going to another spot, and the throttle cables. Personally, I think nitrous is a bit excessive and for all the power we're getting out of the car, it's not worth the 100 bucks.

I don't think the nitrous system is a performance boost even on its own, it weighs 6 ounces so it would probably slow the car down more than it adds to it, even in the best of circumstances. Same goes for "superchargers."

It would be way more effective to just go with a slightly more powerful nitro engine if increasing the car's power-to-weight ratio were my goal.

The point is to build the world's most over-designed RC car. I'll find a way to make it all fit. nitrous in the battery tray, battery over the front bumper, receiver and ESC stuck on wherever there's a flat spot left.
 
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