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1/8, 1/6 and larger scale Trux! Discuss your large scale projects here, 1/8, 1/6 and larger scales. Juggy, TXT, Clod, TF, MF and similar based rigs.


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  #1  
Old 07-20-2012, 07:21 AM
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Default OS 1/8 Raptor

Now that things have settled in family-wise, time to get back to building.

Parts are coming in...been wanting to try this for a long time, and seems like 1/8 is the way to go.

So, the plan is to have a nitro engine up front, driving a 3 speed tranny for manual shifting. I'm debating a few things...

2 or 4 wheel drive? I like the idea of a 2 wheel drive higher speed truck kicking out rooster tails. This won't exactly be a trail truck per-se, so not sure that I want to bother with a full 4WD set-up due to the added weight and complexity. I do have all the parts ready to do it though should i decide to go this route.

IFS or solid axles? I'd really like to go with an IFS for scale looks. Not sure how I'm going to cram it all in there though. Solid axles would be a lot simpler, and save me a ton of room. I've wanted to build a solid axle nitro scaler for a while, but with the raptor body, it's really not going to look right.

Motor: got this one figured out. I've been looking for a good 4 stroke for years - an older FS .40 or .26 PS would have been perfect, but it's just not meant to be. Adapting an airplane engine just led to too many challenges, so I settled on a Supertigre .18 marine motor for a couple of reasons.
  • .18's have a good amount of torque for their size - figure if it can push my Revo to about 40, should have no issues with a scale truck.
  • A marine motor is more compact due to the size of the cooling head so it can fit better on the chassis.
  • Finally, since it is water cooled, lends itself to a radiator set-up.
  • Also, it was cheap so if the entire project goes off the rails (entirely possible...) I'm not out $400 for a motor I can't use.

The only other issue I've been wrestling with is lack of reverse. While I could have accomodated it fairly easily with a Revo, Maxx or Savage transmission I thought the cool factor of the manual shift tranny outweighed the lack of reverse. If i were building more of a trail truck, a 3-speed auto Savage tranny with reverse module would have been the way to go. But since I'll just be tooling around the backyard, think I'll be ok. Will have a nice low first gear for noodling around - just have to plan my route so I don't endo onto something.

Think this is going to be a fun project. Along with the standard larger scale issues of building a chassis, fitting a suspension, etc I've also got things to plan out including water cooling, clutch, fuel tank and exhaust. Even heat shielding... a hot exhaust manifold cold wreak havoc on an ABS body. I'm sure there's going to be lot of trial and error here. Always wanted to build a muffler.

I have no pics yet, everything is still in my head and the body won't be here till Monday. I can start mocking a few things up this weekend though - should at least be able to get the nitro motor mounted up and get an idea of what's going to fit together. As of right now, leaning towards going 4 wheel drive/indy front.

Do have the motor and some of the cooling goodies...been a long time since I even started a nitro:
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Last edited by OldSchoolRC1 : 07-27-2012 at 09:17 AM.
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  #2  
Old 07-20-2012, 02:06 PM
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This is going to be good
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Old 07-20-2012, 03:34 PM
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Old 07-21-2012, 08:02 AM
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OK for this build I have loads of advice as I have done something like this with a 1/8th Chevy SS/R back in 2004,

Since no one had a good live rear axle I used a E-maxx rear end and most of its suspension works. I just fuel tubed some rustler shocks for a lower ride. But now you have a lot more to work with. If you are going 2wd route, Leaf spring it. You will be happy.

Gear box. Since you are dead set on nitro (I was at one time too) Here are your best bets. Go electric!. But seriously. The tamiya gear box is what you want mostly. It can shift under load both up and down and I know that that little .18 does not have the power of my 11.1v brush-less so I doubt it will lunch the gear box....ever. If you use a stck radio I will send you my shift gate. That will simulate your gas/clutch pedel work in a real truck. Coolish, but not needed.

IFS A rustler front end will do. Even better is a RC-10 front end with Traxxas hardware (to keep it all metric) You will have to make your own shocktowers on both.

Water cooled. Here will be your pain in the ***. You can not store enough water in radiator and lines to keep this motor cool. You will need a extra tank in the range of 130-180 ml (this accounts for the in tank pump) I have learned this the hard way before. You will need either a 3-9v pump or a 2 single voltage pumps. Also a single stage cooling system will not due. You need to know what temps to run this motor at its best are. say 225-255 You need to have a first stage low flow that kicks on at 200 and then a second stage that kicks on at 245. So say at 200 it starts a single pump at 4v and then at 245 it kicks it up to 9v for more flow (or first pump on at 200 and second pump on at 245) The reason is if your motor runs to cool it will die just the same as to hot. So having a always on system will not end well. If you want you can make a very simple speed control that is controlled by the motor temp (Let me know if you need one. I will have a buddy make one for you. He made mine in the past) Also you will need a fan a PC 5v laptop fan works great. That is for your radiator.

I hate to be a downer but I think I mentioned in one of your other post that You will not be able to build a exhaust for this motor. (Not unless you have a masters degree in waveform sound waves ) Use a .18 tune pipe and add a stinger to get it down to the ground and call it a day. You will save you and your motor a ton of heartache. And you will get to keep all that yummy power. (You can also prove me wrong and do it any way. I am a big fan of that idea too! )

I am looking forward to this build. I love nitro scale rigs. I like the noise. I like the smoke. But I will still stay DC powered. (I did try to build a hybrid.... I hit it with a 18lb sledge hammer since it ****ed me off way to much during the build.) So keep up the good work. I will find the notebook of what I did back on that SS/R and I will let you know if I find anything new. Cheers!
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Old 07-22-2012, 01:24 PM
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Here's where I started yesterday - got most of the components together to start piecing things togeether. Sacrificed my super nitro rally for the build.


Built up the semi tranny, and lopped the top of the case off so I could make pinion adjustments. Glued the top together and I'll make little brackets to hold it on when running. Need to do this to my Dodge too.


Original mockup...w/o the body, didn't quite know what would fit where. But this was the original plan


Washed up, went upstairs and lo and behold, the body the body had arrived early! Hmm...back downstairs


Checking axle fitment...not bad.



After laying it all out, I didn't have anough room for the tranny, transfer cage, and engine. It would have been too tall to squeeze under the body, even if i had gone with solid axles. I could have gotten rid of the three speed and used an e-maxx tranny to do either suspension combo, but I really wanted the nitro/3 speed so it stayed. So I'm using the three speed tranny for now and going with 2 wheel drive. I'm using front end 4wd mechanicals though for the IFS so if something occurs to me later, maybe I can add it in. (A semijoe dual output would be perfect!!)

Beginnings of the chassis...usually I plan it all out first but threw that out the window and just started winging it. As usual, I'm sure this will be a V1.

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Old 07-26-2012, 01:48 PM
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So now I'm torn...

Debating switching to electric. The nitro\tranny combo will end up somewhere. Not sure where yet, but rest assured it's not going away as it's something I've wanted to do for a while. Need to give it thought - not pleased at the fit under the body and the drivetrain...that three speed takes up a TON of space and combined with the nitro motor and gears...well, it's awful tight in there.

3 speed would stay as I have a spare, and with an electric set-up, I can fit everything in much better. 4wd - no problem. Everything else is totally up in the air at the moment. Need to think about it while shovelling tonight.
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Old 07-26-2012, 03:55 PM
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Does the nitro fit under body as you have it layed out ?
Whats stopping you from getting a pass thru for the 3 speed ?
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Old 07-26-2012, 05:25 PM
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Yes, it fits ok. Would love a pass through, would solve a ton of problems...but they are a little hard to come by.
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Old 07-27-2012, 07:23 AM
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I've shovelled. Decided to switch to electric.

To be clear, for this build it's not an issue with the nitro-motor per se, it just that the layout is less than optimal. I can squeeze most everything in there, but there's a lot less room in there than I thought now that the body has arrived. Can't quite get everything I wanted to do in there....and this body looks great. Deserves a good looking chassis!

So, new (fluid) plan: 3 speed is staying, and 4wd with IFS will be back. 2/4 wheel drive T-case also. Have another 650 motor ready to go....Basically, it's going to be very similiar to my big Ram, but incorperating all the new ideas I've had along the way.

For closure on the nitro motor, it WILL be in a scaler..just not this one. If nothing else for the design excercise. Something bigger and simpler. Fabbing in the IFS for this truck was always part of the plan, but it made things a pain with the bigger nitro motor. Solid axles are the way to go, and my Wraith will be donating some axles (since I cannot stand the body/cage set-up..but I love the axles!) Just ordered something interesting for it, but that's for another build thread.
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Old 07-27-2012, 08:17 AM
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just to keep you on track, i have been wanting to do a similar truck. with nitro upfront, and IFS/live axle

can you not lay over the motor to give yourself more room? thats what i was planning on doing. throw it right up front. gearbox right behind it, in its appropriate place, and then potentially a transfer case, or just straight back to the axle.

i wanna see this happen. to give me inspiration to put mine into gear!
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Old 07-27-2012, 09:22 AM
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Could. Cooling head would have to be reconfigured somewhat - believe I could just rotate it 90 degress. Plus, the exhaust header would either be right against the hood or pointing down and coming out by the tranny. Either way is not good. If I decided to bag the three-speed, it would be cake squeezing it in there. But i want the nitro/shifting ability, so it had to stay.

Happy with the changes, you'll see why over the next week or so.
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Old 07-29-2012, 12:46 PM
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Now that I'm back to electric, have a few progress pics. Thought I'd document the chassis build since I've never really done so. Don't use any fancy tools, just a jigsaw and drills...

First off, need a plan. I usually get out some graph paper and pencils and trace over the countours of the body. Then, I lay out the components of the build to get an idea of what goes where. It's a bit of trial and error, but it's usually a good starting point. Had the Ram sitting next to me as I designed. Went with single TVP's this time around for both simplicity's sake and both tranny's fit. in the same space (the Ram's WK t-case made it tricky)


Once I have the basic chassis shape laid out, I transfer over the design to whatever I'm working with - in this case, 2mm 6061. Usually I scribe in the chassis shape as pencil or ink can get rubbed off.


Once it's laid out, it's jigsaw time. I've learned to take my time to get lines as stright as possible - saves a ton of time later - and use some oil on the blade to cut more smoothly. Still tough though, I'm not exactly a master at it. Here are the parts after the rough cut


Then what I do is drill some holes to bolt the parts together. This way, when filing and drilling later everything stays nice and square. I udes to use a plain old hand drill back in the day, but now I invested in a drill press. Still can't drill holes in a straight line, but at least they are all square and the same from side to side..and the drill press make it a lot quicker.


Once they are bolted together, I drill most of the holes I'll need and break out the files to smooth the edges and get them to the same shape. This is where taking your time to be sure the cuts are a staight as possible pays off. Filing takes forever, and while I used to make the TVP plates were 100% identical, I no longer bother. As long as they are close, smoothed over and look decent, I'm good. The holes are square, so everything bolts up staight and that's all that matters.


End results after sanding odd the flashing and smoothing over the cuts with some sandpaper. :



Now here's where it gets tricky. What looks good on paper doesn't always look good once it's mounted up. Again, a little trial and error. After I got the chassis under the body, I had way too much underhang under the body (forgot to get a pic) Again, looked ok on paper, but looked a little goofy under the truck. So, I lopped off about 3/4 inch and redrilled some of the holes. After building quite a few chassis, I've come to expect this - I almost never hit it right the first try. I should really template it out first, but I'm usually in "go mode" and just do it on the fly.


Final placement under the body. may need fine tuning later, but good though to start bolting parts to!


Next: Skid and front IFS mount. This part is always tricky, it's very easy to screw it up. Trying for all 1 piece though it will have 4 bends in it as well as 2 different widths, holes for the diff and steering, and a pass though for the driveshaft.... This one I will be templating.
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Old 07-31-2012, 08:50 AM
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time for CAD (cardboard aided design) i've come up with some unique pieces that i was pretty sure i could get out of one plate that way.
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Old 07-31-2012, 10:01 AM
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Cardboard aided design!?

Yeah that's how I roll as well!
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Old 08-01-2012, 09:19 PM
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Bent up and hacked out a front skid. Front suspension is bolted on.


However, it's very much sitting "tall in the saddle." Issue is the front suspension does not have a lot of downtravel as is. That's about the total dropout I want from the suspension in the front as it is sitting, but the arms won't get me there.


That's as far up as I can tuck it as is. Again, looked fine on paper, but once assembled - not so much. Note the angle on the arms....it's almost parallel. No more downtravel, but it has gobs up uptravel....in fact, the tires rub the upper wheelwells. Hmm..There's more travel in there somewhere.


So, next step is to get some more downtravel out of the front suspension, then I'll re-bend the plate a bit to tuck it up higher. Looking to go up at least an inch. I have a few HPI MT parts which should be a direct swap with the redcat suspension. Or I've fitted Wild dagger arms on there too. I figure I get a ton of downtravel with my Ram's HPI set-up, so it's here somewhere I just have to find it.

I'll tinker around and see what I can come up with.

On a techie note, I just ordered a linear servo conversion for the shift servo. Thought it would be cool to play with, and a better match for the linear rod of the three-speed. We'll see how it works out.
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