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RE: Nitro Rock Crawlers Only - 1/23/2008 11:16:50 AM   
rickster3057


 

Posts: 182
Joined: 12/11/2007
From: weymouth, UNITED KINGDOM
Status: offline 		Hi ridgewalker,sorry i dont have the link I typed cat 740 in google images and came across a model expo in germany.
There is a company in germany that does manufacture the hydraulic systems, just havnt found it again yet,LOL.
If i come across the link i will post it.
Rickster3057.

(in reply to ridgewalker)
       Post #: 301

RE: Nitro Rock Crawlers Only - 1/23/2008 2:35:32 PM   
Anomie



Posts: 3353
Joined: 4/15/2005
From: Liverwurst, CA, USA
Status: offline
quote:

ORIGINAL: dacaur

Guys, I'm thinking the turbine is a bad idea for a few reasons. #1 is noise. ever been around an RC turbine? They aren't quiet. Second is the exhaust. its really really hot, point it down and it scorches the rocks, starts fires. point it up and eventually a person WILL get burned by it, plus it will have a tendency to push the truck away from whatever direction its pointed so that will make things tough. And third, have you even seen a turbine plane crash? Big fire. These things can malfunction, especially if they happen to roll down a big hill.... Boom.... Just run the hydrolics off a big gas engine.


This is so true. I believe the turbine would be a great experiment and probably a heck of a conversation piece, but nothing practical of course. To me, the sound of a turbine (especially a scale model) just can't be matched. I have a video of a Pahl turbine remote start while mounted to a bench. I'll put the link up this evening.

Back on the subject, the hydro ideas for a crawler are also pretty trick. I think gearing a pump off a nitro motor would not be too difficult. It's all going to be custom fab work, of course, but it seems like something that can be done with reasonable efficiency.

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(in reply to dacaur)
       Post #: 302

RE: Nitro Rock Crawlers Only - 1/24/2008 5:15:35 PM   
rickster3057


 

Posts: 182
Joined: 12/11/2007
From: weymouth, UNITED KINGDOM
Status: offline 		Hi Guys, i found the company that do all the hydrualispares ,also they do hydraulic pre-made axles, pumps, pipeing rams the works, i have emailled them and they are translating a copy its in spanish, of there pricelist and products list for me, said it will be a week, as soon as i get the details i will post it for you.
Reiko looking at some of the products they do it wouldnt be that hard, if you used a crawler chassis fitted the axles all you would have to do is mount the tank and instead of links have rams,the pumps run on electric motors so its even a conversion for the electric guys,hydraulic could be the way.
A geared helicopter motor would be more than powerfull enough and relatively quiet.
Also in answer to a weight issue, 21lb anchor was mentioned i believe, the axles are the same material as the electric crawlers just painted yellow!!!!!!!
I would take that as viable nitro crawler wouldnt you?????
Rickster3057

(in reply to Anomie)
       Post #: 303

RE: Nitro Rock Crawlers Only - 3/31/2008 10:39:43 PM   
RootesMan


 

Posts: 3
Joined: 12/18/2007
From: , UNITED KINGDOM
Status: offline 		Guys,

I've been considering a nitro crawler / mud plugger for a while now and this thread has been very helpful in guiding my thoughts. I work in embedded control - the sort of technology you see in failsafes and HPI's new traction control for drifters. I'm pretty convinced that a nitro crawler can be made to work, so long as

1) The clutch bite is made as wide as possible - ie full bite only towards the top end of the rev range

....and...

2) The throttle and brake are controlled via a unit that takes inputs from the controller AND a shaft encoder on the prop shaft that gives an acurate indication of wheel speed. I'll call this the Nitro-ESC.

I have a feeling that the Nitro-ESC would need to control the brake and throttle separately - May need a big servo ( for instance the HPI Baja Steering servo ) on the brake to stop rolling backwards down hills.

Of course, the clutch would need one hella cooling but I reckon a setup similar to helicopters would work: A shrouded fan attached to the flywheel, sucks air through a second shroud around the cylinder head and then pumps the warmed air across a specially fabricated clutch.

The big question is whether a "servo control" system could control engine revs closely enough - Nitro engines are notorious in their slow response to throttle input and the control loop timing would only be as good as the slowest element in the system. By "servo control", I mean a system that controls a variable to within specified limits by making calculations based on its inputs. An example would be what we RC nuts call a servo. The receiver sends signals to the servo, telling it where it should be. the servo decodes these signals and then moves the motor so that it moves in towards the desired angle. The servo controller looks at the input from the potentiometer until it gets a value it wants and then stops. Most servo controllers are really bad at their job but they can be exceptionally good. Ever seen the controller for the rotation of a tank turret? You twiddle a little doo-hickey and 10 tons of iron moves to exactly where you want it as quickly as it can.

Anyway. If there's still anybody following this thread, I'd be keen to know your thoughts.

Cheers!

R tesMan

(in reply to rickster3057)
       Post #: 304

RE: Nitro Rock Crawlers Only - 4/1/2008 1:15:24 AM   
dacaur



Posts: 863
Joined: 4/18/2005
From: midvale, UT, USA
Status: offline 		That still leaves the problem of an annoyingly loud engine spitting fuel all over the rocks making them slick... nitro rock crawlers might be made to work, but they will never work as well as an electric, and will never be welcome where electric rock crawlers are run due to basically ruining any site they are run at with nitro residue.... Not being rude, just realistic. I'm sure when you show up somewhere with a nitro rock crawler the initial reaction will be "wow" Cool!!" ETC... but it wont take long for the noise and nitro fuel all over the rocks to get on every ones nerves... Now here's another problem many people dont think about, when you are driving a rock crawler you are probably standing just a few feet away from it. Imagine a nitro engine running full speed right next to you... can you say hearing damage?

(in reply to RootesMan)
       Post #: 305

RE: Nitro Rock Crawlers Only - 4/1/2008 4:43:22 AM   
RootesMan


 

Posts: 3
Joined: 12/18/2007
From: , UNITED KINGDOM
Status: offline 		That's a very interesting perspective. Yeah. I'm not sure electric and nitro rock crawlers could co-exist. Can't help thinking the attractions of the activities are somewhat mutually exclusive. ie Electric rock crawler drivers seem to pride themselves in their skill and finesse. I can't help but think nitro crawling would be more like 1:1. Mainly balls-out power. Plenty of skill too but not much finesse. the oil problems aren't insurmountable. Could organise an oil trap. In my experience, nitro residue tends to disapear within a few days from concrete and stone. Probably through bacterial action, so so long as competitions aren't concurrent, there shouldn't be a problem.

As for the noise, I thought that was the whole idea!!

Many thanks for your input.

R tesMan

< Message edited by RootesMan -- 4/1/2008 4:44:04 AM >

(in reply to dacaur)
       Post #: 306

RE: Nitro Rock Crawlers Only - 4/1/2008 2:54:45 PM   
Anomie



Posts: 3353
Joined: 4/15/2005
From: Liverwurst, CA, USA
Status: offline
quote:

ORIGINAL: dacaur

That still leaves the problem of an annoyingly loud engine spitting fuel all over the rocks making them slick... nitro rock crawlers might be made to work, but they will never work as well as an electric, and will never be welcome where electric rock crawlers are run due to basically ruining any site they are run at with nitro residue.... Not being rude, just realistic. I'm sure when you show up somewhere with a nitro rock crawler the initial reaction will be "wow" Cool!!" ETC... but it wont take long for the noise and nitro fuel all over the rocks to get on every ones nerves... Now here's another problem many people dont think about, when you are driving a rock crawler you are probably standing just a few feet away from it. Imagine a nitro engine running full speed right next to you... can you say hearing damage?


All very good points, and also good reasons why the nitro powered crawler will not likely compete anytime soon (or at all). I think the challenge of merely making a reliable system and overcoming all of the difficulties inherent in this idea is tough enough. Attempting to compete with electric power is just not realistic.

Also, for me, a four-stroke powerplant operating at lower (i.e. 2000-8000rpm) speed seems that it would yield a nicer exhaust note when compared to the outrageous engine speed of a two-stroke car unit. This might be something cool to hear, and may also effectively minimize the mess

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RE: Nitro Rock Crawlers Only - 4/2/2008 8:42:20 PM   
RootesMan


 

Posts: 3
Joined: 12/18/2007
From: , UNITED KINGDOM
Status: offline 		Well, as I say, I have a feeling that, if ever IC-engined crawlers were to become available, they would be unlikely to go head-to-head in competition. They're just too different. But that's not to say that the concept is invalid or that it could not become popular. Right now, 1:1 crawlers are, at least predominantly IC-powered but I see no reason why, at some time in the not-too-distant future, we should not see 1:1 crawlers using at least hybrid drives if not pure electric setups from the larger current hybrid vehicles. Lexus' LS600h has an electric motor rated at over 150hp. Line up a few of them in a 1:1 crawler and you've got potent crawling material. OK, so you'd need 5000 cellphone batteries but, hey, people throw them away all the time.

This is a perfect illustration of how one technology replaces another in the mainstream, but you have to remember, there will be areas where the less prevalent technology will have an advantage, albeit maybe small and maybe shrinking. Typical example would be all of the industries associated with riding horses at the beginning of the last century when horses, as a mode of transport were displaced by the automobile. Everything from the people who dealt with millions of tons of manure to the companies who made saddles and buggies. Did they go out of business? Well, some did, it's true, but most used their expertise to refocus into other industries and one or two kept on doing what they did best and did it even better. I'd be prepared to bet that, if you asked the average 1:1 crawler driver now whether he'd like to drive an electric car to stay competitive he'd say no. Let's just remind ourselves what 1:1 crawling is all about:

http://www.youtube.com/watch?v=8xEiCZADpGw&feature=related

These guys aren't going to be satisfied with whizzing motors, no matter how deftly they climb. I can hear both the readers saying "Make yer point, Dummy!" Well, just as the current generation of crawler driver will probably start a breakaway faction for IC-engines only, it's reasonable to assume that a nitro crawler faction could spawn from the current crawler boom. Actually, I'd prefer to call these vehicles something else and I've so far come up with "Sludger", implying a far muddier persuit. Any other suggestions welcome.

Well, that was a long tirade. I'm not sorry if you lost interest but I am if it sounds like a lecture or if I failed to make myslef clear. I'm dead set on building one of these things and, hopefully it'll be alot of fun to build and to drive. I hope that some people will join me on my journey but if they don't I won't be sad for long - I'll be too busy spraying myself with mud!

Oh, and by the way, anyone whose hackles have risen while they read this, please remember; Not one inch of progress was ever made without challenging the orthodox belief of the day.

We have an interesting discussion going on on a crawling forum over here in the UK. If you'd like to join in it's at:

http://www.ukrcrc.com/forum/viewtopic.php?t=2566&postdays=0&postorder=asc&start=0

All the best!

R tesMan

(in reply to Anomie)
       Post #: 308

RE: Nitro Rock Crawlers Only - 4/7/2008 1:02:54 AM   
madfours


 

Posts: 5
Joined: 4/7/2008
From: Springfield, MA, USA
Status: offline 		Hey guys, been checking this post now and again and though I might share what I have so far. I'm not sure if I'd consider it a crawler yet, but it's currently, a geared-down, 4-stroke front-engine truck. I was looking to come up with something with a more realistic driveline with the engine in front, fuel in back , etc. Current weight distribution is very near 50/50. Also I got tired of the 40mph 2-stroke rollovers. To some of your points, a nitro crawler might be possible, but quite a bit of work. There was some talk of nitro engine noise, with a 4-stroke this is not a problem, this truck runs very quietly. I made up an exhaust system to get the fuel residue to the rear, and for a more scale appearance. As someone stated earlier, 4-strokes have a much lower rpm, which helps with gearing, but makes clutching difficult. I had to fabricate steel clutch shoes and a steel flywheel. The heavy clutch shoes grab at very low rpm, and the heavy flywheel allows for idle rpm of about 1500 without loading up. The biggest issue I can see right now is some sort of hill brake to keep the truck from rolling back. You might be able to set up the brakes so they are on at idle, but it will be difficult to maintain this adjustment and the engine may stall if brakes come on too quickly. Anyway, great thread guys, keep the ideas flowing.

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(in reply to RootesMan)
       Post #: 309

RE: Nitro Rock Crawlers Only - 4/7/2008 8:11:19 PM   
Anomie



Posts: 3353
Joined: 4/15/2005
From: Liverwurst, CA, USA
Status: offline 		Welcome, and thanks for sharing your project with us! That is a very cool truck

Your drivetrain is very similar to that which I am building. Front-mounted 4-stroke with a long exhaust has been my idea of choice also. The lengthy pipes can really drop the exhaust note to a minimum. I also see that you have a center mounted disc brake. Do you have any trouble controlling the brake/throttle combo?

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RE: Nitro Rock Crawlers Only - 4/7/2008 9:14:04 PM   
madfours


 

Posts: 5
Joined: 4/7/2008
From: Springfield, MA, USA
Status: offline 		Reiko,
Very impressive work on your truck. Your posts have been very informative.
As far as the brake control, I have not really made an attempt yet to see if it will hold on an incline. It is currently set up for a slight hold at idle. I believe if I trimmed out the brakes some more, I can get there. As long as you have a decent radio with endpoint and dual rate it should work. The other option I have may be to move the brake to the input shaft of the chain drive where I will have the benefit of the gear reduction. I am just using a Futaba 3PM, and it does more than I need. The only problem I had early on was the fact the original Mad Force drive cup had a one-way bearing in it, so I only had brakes in the front. I ended up fabricating a solid drive cup and keying directly to the output shaft. Oddly enough, right now because of the heavyweight clutch shoes and heavy flywheel, theres quite a bit of engine braking at higher speeds because the shoes take so long to disengage. I am still experimenting with shoe weight and spring preload, but I found unless you add some shoe weight, the 4-stroke cannot generate enough rpm to keep the clutch from slipping no matter how light of a spring you put in there. I tried aluminum shoes without a spring and could barely get the truck to move. Once I put the steel shoes in, I could burn the tires off if I wanted to. Plus, being made out of stainless steel, they should wear forever. I'd much rather replace the off-the shelf clutch bell than make a new set of shoes, that was a PIA.

(in reply to Anomie)
       Post #: 311

RE: Nitro Rock Crawlers Only - 4/8/2008 2:18:24 PM   
Anomie



Posts: 3353
Joined: 4/15/2005
From: Liverwurst, CA, USA
Status: offline 		Did you model your clutch shoes after any manufactured unit, or did you just make them to fit the bell? I was considering picking up an aftermarket clutch, like something pretty stout from a 1/8 buggy, and then using that as a basis for making a suitable clutch that will fit my truck.

Also, if you do move your brake to the chain drive input, I would think you'll achieve somewhat smoother braking as you'll be slowing the faster shaft and there would seem to be less potential for 'jerking' the drivetrain if the brake gets a bit grabby. That sounds like a good idea. Either way, I think it's going to be an uphill battle learning to feather the brake and keep the vehicle from behaving badly on an incline

How much does that truck weigh, anyway?

I have to say, it's really nice to see a project as far along as yours. That really is some innovative work you've done there

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       Post #: 312

RE: Nitro Rock Crawlers Only - 4/8/2008 5:37:28 PM   
madfours


 

Posts: 5
Joined: 4/7/2008
From: Springfield, MA, USA
Status: offline 		The clutch shoes are based on a 2-shoe Kyosho clutch, but designed to work with the ID of the clutchbell and the pin spacing of the flywheel I made. I had a Duratrax 14t clutchbell from an