Underground Crawlers F-4 Chassis Design

[C*H*U*D]

I broke my USB flash drive a few weeks back with all my files for my current PSC build. I've had an electrical engineer friend at work trying to fix it, but it's not looking promising......if you keep a lot of your work on a flash drive, BACK UP FREQUENTLY!!!

While waiting for the flash drive fix, I decided to put together a quick crawler so I could play around a bit. I had a set of Axial axles, and transmission so they were what I decided to use. I also had a set of RC4WD 4" shocks, stock Axial rims and 4 Rovers.

I first decided on a more scale truck since I've been having a lot of fun with toybuilder's SCX. I couldn't get anything to look right with the 4" shocks. About 11:30 and 5 beers into a six pack, I decided screw the scale chassis, and just put together anything that I could throw on to the mill the next day. Here is what I started with, and what I came up with:








That night, toybuilder came over and helped with getting it all wired up and ready to run. Thanks Clint . I didn't bother too much with anything permanent since I knew I'd probably change things eventually. The next day I took it out to see how things ran:






Then I stopped by toybuilders house to try things out on his rocks.







It worked pretty good considering it was thought up, thrown together and driven in three days. It was heavier than it needed to be, and also wider. The stock Axial rims are already giving up, but I really like the tires. That's it so far.

[C*H*U*D]

So the old one worked ok, but I really thought it could lose some weight. Another late night, and I had this one mocked up and on the mill the next day. Here is a comparison of the new with the rear end hooked up and the old with the front still attached:






Again, I wasn't too concerned about proper mounting of all my electronics, so that's why it looks "thrown together". I like this chassis much better.
















A few things I need to do is machine a new set of rims.....these are stripping so bad that they are almost useless. I also want to 4-link it, so I'll machine up some new mounts and eventually I want to make a bolt on tube chassis for the top. I think I prefer scalers more, but this thing is a lot of fun to goof around with.

Thanks for checking it out.

[team3six]

Looks good man. More like a Monster truck than a Crawler but hey the best ides are found by accident. if it works than it works ya know.

Shooting you a P.M.

[666]

Can you fit a dig unit? How about a Puller?

[goodoldlevi]

Looks good, I wish I had a mill

[bayouhazard]

That looks pretty good! How wide is that chassis and what's your wheel base on it? Shoot some pics of the underside!

I like the action shots of the tires spinning. The front tires look like there spinng faster than the rear. Do you have overdrive gears in the front?

[C*H*U*D]

Originally Posted by team3six

Looks good man. More like a Monster truck than a Crawler but hey the best ides are found by accident. if it works than it works ya know.

Shooting you a P.M.

Damn Norm....I was shooting for Mall Cruiser! Which one looks Monster Truckish...the first, second or both? I guess that's what happens when IPA is your design consultant.

Originally Posted by 666

Can you fit a dig unit? How about a Puller?

Honestly I don't know. I just made this as a basher....I don't have a dig unit, so I wasn't thinking about that when I designed it. The plates are 2.3" from inside to inside if that gives you any info. Could be made wider, and I think I can also get it narrower.

Originally Posted by goodoldlevi

Looks good, I wish I had a mill

Pretty handy to say the least.

Originally Posted by bayouhazard

That looks pretty good! How wide is that chassis and what's your wheel base on it? Shoot some pics of the underside!

I like the action shots of the tires spinning. The front tires look like there spinng faster than the rear. Do you have overdrive gears in the front?

Here are some of the underside, and some measurements of the width and height. The ratios are both the same, but I might put overdrive gears in. The wheelbase is 12.5" as well

Some things need to be changed of course like the mounting, and the hardware that is used.....this is all 4-40 links which I had laying around, but I plan to make it all metric. That's why there is no countersunk screws since metric uses 90 degree countersinks, and 4-40 does not.

I plan to rebuild the shocks soon, so if there is any interest I'll take pictures of the chassis stripped. If not, I'll post in a week or two with my first basher tube cage. Hope I don't burn myself.

[bayouhazard]

That looks pretty good. Somewhat of a narrow chassis, and I think 2.5 gc is a good all around number. A basher would be badass with a puller motor in there! I don't see why you couldnt? It may get in the way of your upper link though. vWhats the total weight of your rig and how much of that is on the front axle

Threre seemes to be a lot chopped out of the skid plate...

Also you will be very happy with the overdrive gears in the front axle. They work real well with good steering throw, it helps make up for not having dig lol

Good luck with your next build up! Maybe build one more narrower and longer skid?

[toybuilder]

Nice work, Juan That thing is fun to drive!

I think we can shoehorn a puller motor in there. Probably only have to re-drill the skid plate, that might also make room for a dig.

[C*H*U*D]

Originally Posted by toybuilder

Nice work, Juan That thing is fun to drive!

I think we could shoehorn a puller motor in there. Probably only have to re-drill the skid plate, that might also make room for a dig.

Ok, I'm convinced.......If we can't make it fit in this one, I'll make Rev C both DIG and Puller compatible. I'm thinking about getting this guy unless anyone has a better idea:

http://holmeshobbies.com/product.php?productid=132

I don't know anything about DIG either so I'm open for ideas, but right now I'm looking at the DNA unit.

http://stores.homestead.com/hstrial-...tem/Detail.bok

Thanks for the ideas, and putting me more into debt

[Mayze]

Nice work. I'm running the Eritex DIG, and so far, I'm happy with it, but I do wish that Vanquish had their new one out when I bought mine. It looks sooooo nice. Food for thought. You can't go wrong with that puller either. They are stupid powerful. Can't wait to see this build progress!

[C*H*U*D]

So........Norm got me all flustered with the Monster Truck comment and I thought I'd give it another shot.

All dimensions are the same, but I made some cosmetic changes. I figured out how to trim .250" off the width, but figured I would wait until later to do that. I can't afford a DIG unit to check for fit, so that will have to wait too. The old plastic rims are gone......I decided to use my PSC rims, and they work MUCH better. They are also in the pics.

I liked this new design so I made three. I also decided to powder coat it with three different colors. Once toybuilder decides which one he wants, I'll build one of the other colors into my own crawler. I really need to come up with a tube chassis for the top though. I've read through the rules a few times, but still can't figure out how to make this legal. I'll worry about that later. Here are the pictures as of today.













That's it for tonight....I have to go wash the powder out from my toes and grab a beer. Thanks for reading.

[team3six]

Holy, thats a decent looking Chassis you got man. I really like the design. Whats the issue with the rules. it looks to be fine for the width issue. I would say your in the clear. you might have a very nice working chassis that could easily go into production. You should find some testors to give it a try and see what the general thoughts are about it. good job man. Looks great.

[toybuilder]

Nicely done! That powdercoat looks good.

I'm in, thanks for the chance. I'll take the black one or the silver one

Building up a set of axles right now, I'll swing by later and pick up the chassis.

[AliBabba]

If you need a tester, I would be happy to test it out. I am thinking about putting together a rock racer. Seems your idea would work well for it. The 7t puller motor looks awesome too. Nice job.

[C*H*U*D]

Originally Posted by team3six

Whats the issue with the rules. it looks to be fine for the width issue. I would say your in the clear.

Here is the question I have regarding width. My plan is to make a tube chassis similar to the RC4WD DMG tube chassis for their Diablo crawler. The outside measurement of my chassis is 2.55" but the rules state:

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.

If my tube chassis sits inside my frame plates, it would be too narrow correct? If I make it site on the outsides of the plates to meet the 3" overall width rule, would that be allowed?

I have more to do before I worry about rules, so it's not a big issue, but I'd like to know before I go any further. I can make this about .250" narrower, but I'm not sure if it would be worth it.

.

[team3six]

That is true. It has to be a 3" wide chassis from outside to outside. most of the time at the comps I have been to they dont check, but if you can and I would put this into production provided it tests well. if you can hit the specks and fulfill the 2.2 class sizes. then you shouldnt have any problem. I can tell you that it does look to be a pretty decent design. I like the minimal adjustments on the tabs as to not be all nuts like some of these chassis with un nessesary holes. The only thing that I see is that it just elimnates weight issues. Now if you are doing the same by making a tube that fits in the craddle, Then I would experiment with removing more weight from the chassis plates. You'll have the tuber made to bolt on which will keep its strength still. Not sure if its cost effective, but lowering the weight up high is the number one priority since youll be adding it back with a tube.

now just so ya know. My triple S measures 60mm across and holds the tranny nicely. The best bet is to make a mount that holds the tranny closer to the front but not so close as to obstruct the spur gear. Thats why alot of these are designed with the side rail removed on one side. but i have found with a majority of those C design plates that it causes un nessesary flex that does actually effect the way an RC handles. I think the bender chassis was the strongest I found so far. there are many others out there that I havent tryed. but for the most part your common C chassis plate sucks.

[C*H*U*D]

Originally Posted by toybuilder

I'm in, thanks for the chance. I'll take the black one or the silver one

I guess the safe bet is to build up the red one then. I wanted to get a few pictures before I loaded up the electronics so here are some quick ones. Nothing fancy and no action shots, but I'll get some later.

[team3six]

I love red

Juan, I'll admit it! Definatly makes me want one to try it out, How did it seem to handle when you drove it around?.

[C*H*U*D]

Originally Posted by team3six

I love red

Juan, I'll admit it! Definatly makes me want one to try it out, How did it seem to handle when you drove it around?.

I guess ok.....I really don't have any other 2.2's to compare it to though. I swapped the red out for the black chassis the other day. I had to make some motor clearance mods and it was easier to mod the black one since it was already apart. I took it out today at work....seems to work OK. Here is a quick video......can't figure out how to embed youtube videos, so you will have to follow the link. I think it has something to do with HTML being turned off, but I don't know how to change that.


http://www.youtube.com/watch?v=UFUuXXnsJqQ



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