Question from the drawing board....

[toyofast]

Originally Posted by dhyde79

as far as a narrow chassis giving me less hang ups, if I've been running proline rock sliders and haven't gotten them touched yet, I'm sure I can step the chassis out to that width and be fine.

Wait... is this a scale truck? Comp rig? Or just a basher?

Being that you posted this in the "General Tech" section I could only assume it's for a Comp rig and not a scale truck... right? I bet others are thinking this also.

[dhyde79]

General toy, currently it's more comp than anything else, I'm building a scaler too but that's a whole different animal. I'm wanting to use the HR rock racer chassis as my starting point for the new one, it'll be bodyless of course, but a little taller and a bit longer. If there's a way to get it skinnier that'd be fine, I was thinking wider to get the shocks inside the chassis and get the batteries inboard too....but, either way...I'll be going for 1/8" delrin sheet to make the new chassis out of, the cross braces will be 1/4"x1/4" and skid 1/4" delrin. I'm expecting to shave at least 5lbs if not more.....

[Manning]

I wanna see a pic of this 13.7 lb rig.

[dhyde79]

1/8th inch stainless steel chassis plates....that aren't full of holes...lol...also, it should be noted that it's a 14.5" wheelbase 4WS w/dig

You're right though, the battery weighs about what a 6 cell stick pack weighs...

[monkeyracer]

I assume you don't compete with this rig, since your wheelbase is way off the comp-legal limits, and you use rear steer.

Since it's a "basher" and will never see a judges score sheet, then go crazy with your chassis design. Make it 6" wide if you want, you are the only one that will be driving it, and you won't have to compete against anyone, so if you have any performance gains or losses, you're the only one it affects.

Why not make the chassis the stock width, and place the batteries on each side of the chassis sitting on top of the rock sliders? The sliders should protect them from rocks, and allow you to keep the weight low.

Also, when you do decide to buy a battery that fits better, you'll already have a chassis that will work for what you need.

Another thing to keep in mind is the HR chassis is a rip-off of the FLM SPV2 chassis. If you're going to copy one, at least copy the original.


In crawling, weight over the front axle is ideal, but in general bashing a forward bias closer to the center works well. If you go full throttle all day (which it sounds like you do with your run times and gearing...) then think of a traxxas slash. It's got a low cog, and a wide-ass chassis tray. If you find a good in-between from a slash width and a 1" moa chassis, then you'll probably be fine.

Make the chassis, and make a few different width skids, and see what you like the best. You obviously wont be selling this chassis, so since it's for your own use, make it what you want.

[dhyde79]

Originally Posted by monkeyracer

I assume you don't compete with this rig, since your wheelbase is way off the comp-legal limits, and you use rear steer.

Super Class instead of 2.2? (there are other classes ya know ;) )

Originally Posted by monkeyracer

Since it's a "basher" and will never see a judges score sheet, then go crazy with your chassis design. Make it 6" wide if you want, you are the only one that will be driving it, and you won't have to compete against anyone, so if you have any performance gains or losses, you're the only one it affects.

it is more of a basher yes, I prefer to crawl for fun, but, I'm trying to get it back in line with crawling a little better than what the one I built for the wife does lol. it's a bad day when the person building em gets spanked by the one made for the girl that wasn't really sure she wanted one....the only major difference between the two is the weight and placement, and that's gotta change....

Originally Posted by monkeyracer

Why not make the chassis the stock width, and place the batteries on each side of the chassis sitting on top of the rock sliders? The sliders should protect them from rocks, and allow you to keep the weight low.

that's the way it is right now, I was trying to think of a way to protect em a bit more, and wanting to move to a bodiless design, so, having them outside the chassis is gonna be a bad idea...

Originally Posted by monkeyracer

Another thing to keep in mind is the HR chassis is a rip-off of the FLM SPV2 chassis. If you're going to copy one, at least copy the original.

if I had an FLM SPV2 chassis to copy to paper/cut from lexan I would, since I grabbed the HR one cheap on the for sale section on here for the wife, I went with it...(at least I think it's the HR one, it might be the FLM, who knows, the seller didn't say)

Originally Posted by monkeyracer

In crawling, weight over the front axle is ideal, but in general bashing a forward bias closer to the center works well. If you go full throttle all day (which it sounds like you do with your run times and gearing...) then think of a traxxas slash. It's got a low cog, and a wide-ass chassis tray. If you find a good in-between from a slash width and a 1" moa chassis, then you'll probably be fine.

Make the chassis, and make a few different width skids, and see what you like the best. You obviously wont be selling this chassis, so since it's for your own use, make it what you want.

full throttle no, but, I tend to drive it from where I get out of the car to where I'm going to crawl, like you would a 1:1 rig, you drive from where you un-trailer it to where you want to go play in the ORV area or whatnot, if I find something along the way that looks fun, I stop and play on it, and such. also, I originally was setting the crawler up to be more of a rock racer since the puller motors have such good torque low end and with a dual stick I've got plenty of control over tiny amounts of throttle so having some speed isn't necessarily as bad...

as far as comparing to a slash....that might be a good comparison, but, I prefer not to think of traxxass products....they break too easy...thusly I'll think of your comparison to my SC8 ;) the main difference there is, it's wide because it's supposed to be a scaled down CORR truck, and the width is to keep it scaled properly, and a crawler is sized according to what you need it to do performance wise.

another reason I'm considering widening a little is that right now, using HR threaded 120mm shocks in a droop config, on that HR chassis, when you articulate fullly to one direction or the other in the rear, the chassis sometimes catches on the bottom edge of the shock body, and I'd like to make sure that can't happen if I'm building from scratch, even if it's just moving the TVP's out enough that the shocks are fully within the TVP's...

[Terranaut]

13.7lbs. is kinda chubby for a 2.2 based rig, regardless of your longer wheelbase. Most people will be in the region of 5-6lb.. Amp draw is almost proportional to weight. Your gearing is also higher than is common for crawling, that sucks amps too. And LiPo cutoff at 3.3 may be good for batteries but you will not get get all that capacity from your packs. Puting these three together would seem to explain the short runtimes.

Stalled servos can also pull a lot of current, particularly if they're digital. Maybe check your end points just to be sure. It all adds up, seeing that you run three servos.

If your charger has a readout, see how much mAH goes in on a full re-charge, that may tell you something. Your battery should not see much stress in a crawler so you can probably lower your cut-off to 3.0V per cell safely. Follow your nose from there.

Cheers.

[silentcircus]

Originally Posted by dhyde79

close, I'm considerably more worried about not having to buy $399.95 worth of batteries to match my current runtime, as well as having to change the batteries out after each run, than I am about actual runtime. (@ maxamps 1290mah 2S packs would fit on the front axle, 1550s wouldn't so, I'll use them as my basis, to make the same battery capacity as my 6000mah I'd need 4.65 1290's so, I'll say 5 batteries at 79.99 each)

Eighty dollars for a 1300 mah battery? The hell with that! I bought three Holmes Hobbies 1300 25c batteries for just a little more than the price of one of those. And I do change out between rounds, just to keep fresh batteries in it.

http://holmeshobbies.com/product.php...&cat=10&page=1

[Harley]

Super class wheelbase has to be from 16-18"

Minimum wheel size is 3.2" as well.

[monkeyracer]

Originally Posted by dhyde79

Super Class instead of 2.2? (there are other classes ya know ;) )

What he said:

Originally Posted by Harley0706

Super class wheelbase has to be from 16-18"

Minimum wheel size is 3.2" as well.

[dhyde79]

14.5 is just the rear stretched, I'll be stretching the front as well with the change, and as far as fitting super, anything that makes a 2.2 non-legal for 2.2 forces it to super class...and if I could actually find adaptors to get 17mm hex's for the axial axles, I'd gladly put my moabXL's on it too ;)

[Harley]

No, an out of spec 2.2 does not mean it just runs in the super class. You must meet all the super class requirements, including wheelbase and wheel diameter. Trust me, I am part of the USRCCA rules committee.

[dhyde79]

strange.... according to the rules PDF I downloaded a couple months ago, it says the following

Originally Posted by USRCCA RULES PDF

2.2 Class 1 - Super Crawler Class:
• 2.2.1 - No limits on wheelbase, vehicle track width or height.
• 2.2.2 - No limits on tire type or size.
• 2.2.3 - No limits to steering configuration.
• 2.2.4 - Super class bodiless over all dimension of the complete chassis must be at least 12"overall
length, 3" overall width, and 3.75" overall height
• 2.2.5 - If at any point during a run your vehicle falls out of these vehicle specs for any reason you will
be required to take a touch penalty and correct the problem.

2.3 - Class 2 – Class 2.2: If a Class 2 vehicle violates any of the following requirements it must run in Class 1.
• 2.3.1 - Vehicle wheelbase is limited to a maximum of 12.5 inches. This is determined by measuring
from centerline of front axle stub to centerline of rear axle stub, with all the wheels pointing straight
ahead, with the vehicles suspension holding it's own weight.
• 2.3.2 - Vehicle track width is limited to a maximum of 12.5 inches. This is determined by measuring
the bottom of the outer most edge of the front and rear tires while the vehicle is sitting on level
ground.
• 2.3.3 - Vehicle is limited to 2.2 inch wheels/rims or smaller at the bead surface. Wheels may be
modified provided that the tire bead surface does not exceed 2.2 inches in diameter. Tires may be modified from other sized tires using only a pliable rubber but must not exceed a total uncompressed outer diameter of 6 inches.
• 2.3.4 - Vehicles are limited to 2-wheel steering only.
• 2.3.5 - 2.2 Crawler class bodiless overall dimension of the complete chassis must be at least
8"overall length, 3" overall width, and 3.75" overall height.
• 2.3.6 - If at any point during a run your vehicle falls out of these vehicle specs for any reason you will
be required to take a touch penalty and correct the problem.

now of course, going to look at the site that now has a new ruleset that apparently has been posted since the first or so? (correct me if I'm wrong) there are considerable changes to the rules. I've just glanced at them and I can pretty well say that I'll be tossing them since I don't think it's right to go from a "if you don't fit in this class, you move to the next one" class system to a "if you don't fit the one here you have to make it X amount bigger in this dimension, X bigger in another, otherwise you can't run at all" system.

[monkeyracer]

Originally Posted by dhyde79

strange.... according to the rules PDF I downloaded a couple months ago, it says the following



now of course, going to look at the site that now has a new ruleset that apparently has been posted since the first or so? (correct me if I'm wrong) there are considerable changes to the rules. I've just glanced at them and I can pretty well say that I'll be tossing them since I don't think it's right to go from a "if you don't fit in this class, you move to the next one" class system to a "if you don't fit the one here you have to make it X amount bigger in this dimension, X bigger in another, otherwise you can't run at all" system.

Your quote has the 2009 rules, the 2010 rules show all the updated info on the different classes.

The new limits do seem strange, and there are a lot of people that like to build small supers, but the rules are there to prevent a 2.2 beating a Super in a competition, and vice-versa. It used to be a true unlimited class.

Check your local competitions though, they may not care what size your rig is. If you want to compete further than locally, you'll have to build a rig to match the 2010 rules.

[dhyde79]

the last comp I've been able to find that anyone really tried to build up was over a year ago here....I'm working on setting one up at the end of next month....I'll be using the old rules instead of expecting everyone to have read and changed to the new rules that're 10 days old....

either way, mine wasn't built to be a small super, it was built to be fun, when I stretched it I was playing around with WB and seeing how much of a difference it makes.....honestly, my wife's 2.2 legal rig drives places mine can't even consider...for now....but, my stretched WB makes some climbs much easier than what she's able to get up...so, it's a win some lose some deal there....

anyway....back to the original point, the chassis width.....when you guys are going to skinnier chassis, doesn't the fact that with an AX10 based build you end up with the motor hanging out the side of the chassis screw with side to side balance and become more of an issue because of risk of hitting the motor with rocks and such?

[Harley]

Originally Posted by dhyde79

anyway....back to the original point, the chassis width.....when you guys are going to skinnier chassis, doesn't the fact that with an AX10 based build you end up with the motor hanging out the side of the chassis screw with side to side balance and become more of an issue because of risk of hitting the motor with rocks and such?

When I designed the Hybrid chassis (now sold by MSD), I wanted the narrowest chassis I thought was feasible. After spinning the transmission to accommodate a dig it put the motor on the passenger's side. This does make it slightly out of balance but not really noticeable. It actually helps counteract the torque twist though.

I added a small skid plate that bolts on the side to help deflect rocks from hanging on the motor plate. It's not really needed, but was just a fun feature to add.

[dhyde79]

I'm guessing that chassis is one that's designed to have a body put on it.....I'm wanting to build a bodiless one......thoughts? I wouldn't mind putting a bit of a small skid on the side but, without a body on it, if the can's hanging out the side it's gonna look pretty strange, and then adding more material defeats the redesign to lighten the rig too.... :( maybe keep it stock width then.....

I tinkered with taking the HR chassis and putting it on a 1/4" delrin chunk that was stock skid + 1.5" and then mounted the lower links and shocks, articulated it fully and didn't lose any, but, had problems with having to force the last 20 degrees because the shock body was pressing against the inside of the chassis plate, with a decent standoff to the inside of the plates even.....guess I'll be sticking to standard width if there's not a reasonably easy way to make it skinnier....and turning the transmission on its side defeats lightening too cause it moves WAY too much weight up from the skid....

[monkeyracer]

Originally Posted by dhyde79

I'm guessing that chassis is one that's designed to have a body put on it.....I'm wanting to build a bodiless one......thoughts? I wouldn't mind putting a bit of a small skid on the side but, without a body on it, if the can's hanging out the side it's gonna look pretty strange, and then adding more material defeats the redesign to lighten the rig too.... :( maybe keep it stock width then.....

I tinkered with taking the HR chassis and putting it on a 1/4" delrin chunk that was stock skid + 1.5" and then mounted the lower links and shocks, articulated it fully and didn't lose any, but, had problems with having to force the last 20 degrees because the shock body was pressing against the inside of the chassis plate, with a decent standoff to the inside of the plates even.....guess I'll be sticking to standard width if there's not a reasonably easy way to make it skinnier....and turning the transmission on its side defeats lightening too cause it moves WAY too much weight up from the skid....

For the exact reasons you are having issues with the shock bodies and the HR chassis, I designed my QVP (quad vertical plate) bodiless chassis with a wide skid but a narrow cab so that the shocks mount on the outside of the plates.

Build Thread

I'm redesigning the chassis to have a narrower skid, but with side plates to keep it "legal" for the 2010 rules.


If you were to add 1.5" to a stock AX10 skid, you'd be at almost 5 inches wide. Which is a lot, but if you have an extended wheelbase, that makes a little less difference than with the 12.5" WB. With it that long though you might need to make it wider at the wheels to be more stable as well.

[dhyde79]

here's a pic of the prototype.....got it put together (kinda) to see how everything was matching up, wheelbase measures 14.5" and I'd say articulation's nearly 85 degrees....and now, all of the weight is at the axles and the transmission....the only major change I'm looking at is fixing/changing how my lower links are attaching, since right now they're outside (forward and backward, not side to side) and sightly above the skid and that makes the skid a hang up point.....


oh yeah, pic was taken with a cellphone....so....sorry it's not stellar...and sorry if it ends up being huge....

[silentcircus]

Kind of hard to see anything in that pic, maybe another from a different angle in better light?