Rock racer Question

[twors]

How does a rock racer setup differ from a standard crawler setup. Can one truck do both equaly as well. What does a rock racer setup look like. Thanks

[mrpink]

Originally Posted by twors

How does a rock racer setup differ from a standard crawler setup. Can one truck do both equaly as well. What does a rock racer setup look like. Thanks

here is what my 1.9 rock racer looks like:




It is a fun little rig... rc4wd 2 speed trans with a Novak goat BL setup, hauls ass for a crawler.

p!nK

[Da Hermit]

How I am setting up my rock racer is the same as a rock crawler but it goes a lot faster. 7.5 novac, 6000 li-po faster.

Beautful rig mrpink.

[jamesbernatchez]

Here is my rock racer:




It is different from my 1.9 crawler because of faster motor and higher voltage battery. Also this is sprung whereas my crawler's suspension is all droop.

[Mad Scientist]

Rock Crawler/Racers are very similar. In very basic terms, think of rock racers as crawlers that just go fast

[RCMFMaxxMan]

if you are familiar with go-fast rc cars, you just combine those concepts with a crawler. faster motor and stronger parts is a start. You shouldn't be running droop or else when you land a jump there will be nothing to soak up the landing. And also on that note, you want to get as much weight off of the axles as you can. if not, your suspension will be pretty rough because you will have all that weight on the axle with nothing but the tires to absorb shock. this is called unsprung weight. and lastly low cg is more important than ground clearance for rock racers. This is all for a pure rock racer, assuming you wont be trying to comp crawl with it. hope this helps!

[BeeRC]

I'm going to list some ways that I'm wondering if a rock racer setup would differ from a rock crawler. This is more of a question than a proper listing. Maybe you would like to correct the list where It's wrong or add things that have been omitted. RCMF MaxxMan listed some good points for a rock racer. I'll include them in the list. And as Mad Scientist said "think of rock racers as crawlers that just go fast. If you all are willing to refine this list, hopefully we may end up with a good initial setup for rock racers that can be used as a reference when building them ourselves.

Questions:

1. "Keep the weight off the axles as much as possible." Would this include the steering servo and the batteries?

2. To help reduce unsprung weight should heavy aluminum wheels and lead weights be omitted?

3. "Low CG is more important then ground clearance". How is this done in light of items 1 & 2?

4. "Don't use a droop shock setup." Should external springs be used that are stiffer than a crawler would use ?

5. Would it be good to have a wider track width than a crawler wouhavefor better high speed stability?

6. Regarding the motor, what # of turns and winds would be good to start out with?

7. What would be a desireable final drive ratio to shoot for?

8. Retain a front end weight bias or shoot for something closer to 50/50?

9. Use a somewhat firmer tire/foam setup than on a crawler?

10. Volt up? Is this not as important since the gearing probably wouldn't be as low as a crawler?

[RCMFMaxxMan]

Originally Posted by BeeRC

I'm going to list some ways that I'm wondering if a rock racer setup would differ from a rock crawler. This is more of a question than a proper listing. Maybe you would like to correct the list where It's wrong or add things that have been omitted. RCMF MaxxMan listed some good points for a rock racer. I'll include them in the list. And as Mad Scientist said "think of rock racers as crawlers that just go fast. If you all are willing to refine this list, hopefully we may end up with a good initial setup for rock racers that can be used as a reference when building them ourselves.

Questions:

1. "Keep the weight off the axles as much as possible." Would this include the steering servo and the batteries?

2. To help reduce unsprung weight should heavy aluminum wheels and lead weights be omitted?

3. "Low CG is more important then ground clearance". How is this done in light of items 1 & 2?

4. "Don't use a droop shock setup." Should external springs be used that are stiffer than a crawler would use ?

5. Would it be good to have a wider track width than a crawler wouhavefor better high speed stability?

6. Regarding the motor, what # of turns and winds would be good to start out with?

7. What would be a desireable final drive ratio to shoot for?

8. Retain a front end weight bias or shoot for something closer to 50/50?

9. Use a somewhat firmer tire/foam setup than on a crawler?

10. Volt up? Is this not as important since the gearing probably wouldn't be as low as a crawler?

1. batteries, yes. servo, if you want but setting up an inboard servo can be tricky due to space issues and articulation.
2. yes light plastic wheels, no weights.

<>

3. a lower chassis. I would start with the chassis at the same height as the axles and adjust from there.
4. yes the springs will probably be a little bit stiffer depending on your setup. you don't want the chassis to bottom out on landings. oil, as usual, plays an important role too, to slow down the compression. Also, internal springs can still be used but will have to be above the piston instead of below so they are extended at rest, not compressed!
5. yes, wider track width will improve stability at speed.
6. The popular choices are cobalt pullers and mamba 5700. if you can't afford one of these you can try something like a 17t single.
7. not sure. The mamba is pretty fast so if I was using that I would probably gear it as low as possible to get some extra torque and adjust from there. Motors like cobalt pullers that already have oodles of torque can probably handle a bigger pinion and/or smaller spur.
8. 50/50 will give you the best stability when going fast and should keep the flight attitude pretty neutral.
9. the foams will probably be firmer. Its like you don't want to drive your aired down 1:1 tires going 60 haha.
10. I would volt up just for the extra torque and wheel speed. something like an 11.1 lipo would be good since it will be in the chassis where space will be limited.

Keep in mind all of this is for a dedicated rock racer, assuming you don't care how it performs going half a mile per hour or if it can win a crawler comp or not. Basically, take the tech of offroad racing (learn what makes truggies and buggies perform so well on a track) and then apply it to a solid axle rig. It will also depend on how you and/or the people you race with will set up the rock race course. Like how much rock and how much dirt and jumps. What I have been talking about is the extreme example ofa rig for just a dirt track. Comp crawlers would be the extreme for a technical rock course. So you will have to look at the terrain and decide how much rock racer you need and how much crawler you need if any. But a lot people do like to incorporate rocks to keep it interesting.

I hope this helps you all ;)

P.S. keep spare parts on hand!

[Tanis]

Originally Posted by RCMFMaxxMan

1. batteries, yes. servo, if you want but setting up an inboard servo can be tricky due to space issues and articulation.
2. yes light plastic wheels, no weights.

<>

3. a lower chassis. I would start with the chassis at the same height as the axles and adjust from there.
4. yes the springs will probably be a little bit stiffer depending on your setup. you don't want the chassis to bottom out on landings. oil, as usual, plays an important role too, to slow down the compression. Also, internal springs can still be used but will have to be above the piston instead of below so they are extended at rest, not compressed!
5. yes, wider track width will improve stability at speed.
6. The popular choices are cobalt pullers and mamba 5700. if you can't afford one of these you can try something like a 17t single.
7. not sure. The mamba is pretty fast so if I was using that I would probably gear it as low as possible to get some extra torque and adjust from there. Motors like cobalt pullers that already have oodles of torque can probably handle a bigger pinion and/or smaller spur.
8. 50/50 will give you the best stability when going fast and should keep the flight attitude pretty neutral.
9. the foams will probably be firmer. Its like you don't want to drive your aired down 1:1 tires going 60 haha.
10. I would volt up just for the extra torque and wheel speed. something like an 11.1 lipo would be good since it will be in the chassis where space will be limited.

Keep in mind all of this is for a dedicated rock racer, assuming you don't care how it performs going half a mile per hour or if it can win a crawler comp or not. Basically, take the tech of offroad racing (learn what makes truggies and buggies perform so well on a track) and then apply it to a solid axle rig. It will also depend on how you and/or the people you race with will set up the rock race course. Like how much rock and how much dirt and jumps. What I have been talking about is the extreme example ofa rig for just a dirt track. Comp crawlers would be the extreme for a technical rock course. So you will have to look at the terrain and decide how much rock racer you need and how much crawler you need if any. But a lot people do like to incorporate rocks to keep it interesting.

I hope this helps you all ;)

P.S. keep spare parts on hand!

Got a pic of your rig?

[RCMFMaxxMan]

Originally Posted by Tanis

Got a pic of your rig?

you mean my pile? haha I don't have one. at least not completed. I'm working on a 14" mf based racer. I'll probably start a thread soon in the tf section. But yeah I just know a little about how they work. I have had go fast rc's for a long time.

[jamesbernatchez]

One change to the "number of turns to start with" question I would say a 17t motor probably would be too quick with not enough torque. In my rig I posted above I am running an Axial tranny, 13 tooth pinion, High Lift 27 turn stock motor, and 11.1v 3s lipo. I am still able to "crawl" if needed, but have plenty of wheelspeed to jump and bounce down rocky courses. If anything I could possible swap out to a 35 turn and go up on the pinion to a 15 tooth. A 17t probably won't supply enough torque when you actually have to crawl over something rather difficult which will cause your rig to "stall".

[RCMFMaxxMan]

Originally Posted by jamesbernatchez

One change to the "number of turns to start with" question I would say a 17t motor probably would be too quick with not enough torque. In my rig I posted above I am running an Axial tranny, 13 tooth pinion, High Lift 27 turn stock motor, and 11.1v 3s lipo. I am still able to "crawl" if needed, but have plenty of wheelspeed to jump and bounce down rocky courses. If anything I could possible swap out to a 35 turn and go up on the pinion to a 15 tooth. A 17t probably won't supply enough torque when you actually have to crawl over something rather difficult which will cause your rig to "stall".

well as a stated I was talking about a dedicated rock racer, assuming it wouldn't have to crawl very well. But yeah If you want to be able to crawl do something like 27t or 35t. The brushless inrunners though have very smooth throttle wise and are pretty torquey so they aren't that bad at crawling.

[BeeRC]

Any other ideas on this? We should keep adding to this as it will be very helpful for all the potential as well as current rock racers.

[RCMFMaxxMan]

Originally Posted by BeeRC

Any other ideas on this? We should keep adding to this as it will be very helpful for all the potential as well as current rock racers.

i agree but at this point for me my knowledge is only so much since I haven't got a chance to really put anything together yet. I am going on vacation next week until june 25th, but at that point I plan on making a write up on how to create a rock racer. Which should be bigger and more informative with pictures and methods and what not.

But in the mean time, if anyone else has any input, go for it. I would like to hear from wrecker and turtle. hello? where are you guys?

[Cake Eater]

So far the info for a Rock Racer is good.... I believe having a balance of torque and wheel speed is what you want to look for. As well as keeping the 'axles' light and have it set up as a sprung suspension as apposed to a droop (no droop). Keeping the CG low and balance, along with realism, is what i tried to achieve. I had to do that with the electronics and such, since the chassis is solid and probably the heaviest part.

I've set up mine to mimic the 1:1 its designed after. I have the motor and tranny in the center of the chassis with a 7.4v lipo battery towards the rear (where the motor in the 1:1 would be).
I have a Warrior 35 turn motor with a Novak Rooster Crawler, B3 tranny w/ a 21 tooth pinion and 87 tooth spur. Still pleanty of torque thanks to the strong magnets in the motor, and has some good speed because it's a 35t and the gearing. Front and rear are sprung with rally car front shocks and 'front' buggy rear shocks. It's about 75% droop and 25% sprung. My articulation is limited to about 30-35 degrees... I don't feel as though I need much.

[RCMFMaxxMan]

thats an awesome buggy. For me I would have less droop in the shocks but thats just because I like the jumps. does it bottom out often? and what is your driving style with it? i.e. crawling, jumps, rocks, dirt, turns, etc.

[Testykalz]

Cake Eater...that is sweet. I'll have to say you definitely acheived the 1:1 look! I am jealous...I was gonna ask what tube chassis that was and such but I don't have the patience to fit everything nice and neat in there to make it look good! lol


Sweet rig man!

[Brandon]

Nice rig cake eater. Especially the wheel and tire combo

I run a 7t cobalt puller on a 2s lipo
Axial trans 23/71 gearing
60% compression 40% droop.
2" CG
50/50 weight bias
No weight in the wheels or anything extra on the axle.

Works great and is a freaking blast to drive!

[Cake Eater]

Thanks for the comments... I guess driving style would another thing to consider when making a rock racer. I wanted mine to perform well when 'crawling' and to be able to handle some speed for 'racing'. I wouldn't mind having less droop, but I needed that much to still keep it at a scale looking ride height. I built it in mind where function follows form, and them messed with it more and more till more function was achieved. It's set up for the terrain that I run on. A lot of slick style rock, not many sharp edges and not a lot of voids. It does bottom out slightly when jumping, but the tires help absorb the rest of it. It works pretty well.
The chassis was a custom build by Beckworks. Then after many revisions in the links, shocks (5 different shock set ups), wheels, tires, and even electronics, it's where it is today. Lots of trial and error.
It was a bit of a chore to hide as much of the electronics and wiring. The window net helps 'hide' some of it. At least take some of the focus off.

One thing I want to do is get the steering to be better. Ive contimplated unlocking the front or rear diff, but don't know how much that would hurt it's crawling ability. And for that matter, I don't know which diff would be better to unlock. Any thoughts?

I'm not trying to hyjack the thread, there's still a lot of usefull inform about setting up a good rock racer...

[spot me 2]

Here's my 2.2 rockracer. Just build one and have fun with it. These thing are a blast to drive and my setup crawls quite well too. I still need to take some action shots.