Traxxas 4-Tec Conversion
 

Picked up a good deal on a used nitro 4-tec. I told the guy what I didn't need and he lowered the price accordingly. Made me happy as I don't need to find a way to offload the stinky nitro stuff I won't use.

It came looking pretty much like new, except for a little under chassis wear.

First thing I did was lock the two-speed spur into second gear and removed first gear altogether. To lock it, I used the method similar to how I did my Revo wayyy back. A little dremel work, a couple 4mm screws, and a bunch of JB Weld later:

http://scriptasylum.com/forumpics/4tec_1.jpg

Actually, this is V2. V1 had about 1mm of spur wobble that I found unacceptable. V2 was done the same way but more carefully.

I then modded the rear-end a little and make a motor mount out of some 6061-T6 aluminum angle stock:

http://scriptasylum.com/forumpics/4tec_2.jpg

The next two pics show the spur adaptor and optional 45T spur mounted. The 45T is really supposed to be 1st gear, but I made a little spacer (white ring) to make it fit right as 2nd gear.

http://scriptasylum.com/forumpics/4tec_3.jpg

http://scriptasylum.com/forumpics/4tec_4.jpg

This arrangement lets me use pinions ranging from 14T all the way up to around 20T. And they're Mod1.

More updates to follow as I make them. I'm not too gung-ho on this project, but it gives me something to do between doing things to my XT8 project...

Lookin good brian.

Looks good Brian, I know how you feel and bing less than enthusiastic... My 4-tec is just sitting in a box! Maybe it needs a new home?

Anyone want it?

I do like your motor mount Brian, any ideas where/how you will mount the battery?

I wouldnt mind taking it linc. Ill see what I can do with it. Ive got some extra stuff sitting around.

It's not that I don't think it will work well, it's just that it gives me something to work on in between other projects. The weather right now isn't the best for on-road so I have some time.

For some reason, I still have an old emaxx motor mount plate around, so I use that as a template when I dremel out the adjustment slot and shaft collar area. It is a PITA to dremel the slot to be the exact size and arc needed, but not too bad.

I plan on using 3s with a Medusa 36-60-3100 motor. I can technically get a normal ~140mm long pack to fit, but it will hang off the chassis quite a bit. Not only does this look funny, it makes it unbalanced. So, I think I'm gonna get a couple ~1500mAh+ 3s saddlepack size packs and put them in parallel to get the capacity (at least 3Ah) and length I want. I have the whole layout planned out so it's just a matter of looking around. I'm shooting for around 50-60mph so I won't need super heavy duty packs.

Whatcha gonna give me for it?

Depends. As of right now I have some stuff you might want. Ill shoot you a pm in a few.

Unless your talking straight cash?

I put a thread up with pics in the for sale section...

Trades or cash, just Pm me.

Aside from these MA packs, anyone know of a similar lipo that will work?

Max total dimensions I have in my tray area:
100mm X 65mm X whatever.

2 of these in parallel... 3500 mah 25c 3s lipo with 95x35x60 dimensions...

http://www.hobbycity.com/hobbycity/s...5C_Lipoly_Pack

And buy me something nice with the money you saved:lol:

A little more capacity from 2 of these in parallel:

http://www.hobbycity.com/hobbycity/s...y_Pack_w/_Conn

4100 mah 25c 3s with 100x35x56 dimensions.

Little more expensive, like 10 bucks more for the pair:lol:

Honestly ma want 170 bucks for their "stuff". Blows me away.

Thanks, either of those would work fine.

Yeah, I don't understand how MA can charge what they do. They are fast becoming the most expensive lipos you can get. :neutral:

Gotta pay for all of that advertising somehow. Even with their 20% gold member crap (still have to buy a bunch of stuff to get that) they are still double what you pay at HC... At least they sell decent chargers... but those are overpriced too:intello:

Flightpower @ tower is even cheaper - much cheaper no now that there is a clearance sale.

Their chargers minus the 20% discount is about what you'd pay to buy the same thing from mike :yes:

Screw savings, they offer some with 40C discharge.

http://www.trakpower.com/

Hey BG, any more shots of the rest of the chassis? Wondering how you did the servo and front belt mounts...

It's funny, everytime I finish a little project, I pull the 4tec back out and do some more pondering about how things are gonna lay out. After a while, I get discouraged and shelf it again. But just the other day, I had an epiphany!

The problem I had was that I needed a really short lipo. Somewhat easy enough to solve, but I would MUCH rather use regular size lipos (in the 6 NiMH cell size range). But, that stupid side belt!!! Well, this might not be the best way for side to side balance, but here is the plan (and I've already done some of it):

- Move the steering bellcrank to the other side. DONE
- Relocate the steering servo to the middle of the chassis as far right as possible, and extend the steering link. DONE
- Add supports to the front belt mount area. DONE

This will allow plenty of room for the battery on the left side of the chassis. I figure if I mount everything else possible towards the right, it should offset the battery weight. Some preliminary layout experiments look favorable. But, I need a motor where the leads come out the side (hence my email to medusa).

I don't have any fresh pics right now, but I suppose I could snap a couple tonight...

I just finished modding the 2 speed to lock it up. Drilled and tapped a few holes, seems to run true. I am having the same issue as you with battery mounting. However I plan to run 5s, so I may just use some maxamps 2100 cells that I have laying around... A 5s 2100 20c (maybe) lipo will have around the power of a trakpower pack, so hopefully it will work. A 15l may be overkill, but hopefully it will stay cool... Same think with the 9920...

I managed to get the old rcm revo mount to fit the 4-tec chassis... Might even try the tekno mount, although I would like to have some adjustability for gearing. I plan to try a 20/45 to start. Should do around 60 with that. I will get some pics in a thread later...

Here is a snapshot of the chassis layout showing the plans. I tried to get a shot of the ruler to show how much room there is for the motor, but there was too much of a glare.

Sorry about the picture quality, it was taken via my cell...

Looks good Brian. I like how you re-mounted the servo. Must be tight for the linkage going under the front upper deck.

I got the motor mount in and put the center belt back on on mine. Looks like I have enough room to run 6s 2100 maxamps lipos, and I have that many "matched" cells (or at least what maxamps calls matched) so I may have to swap in a quark and give it a try. I will stick to a 5s pack at the moment, and see how it does. 5s and 20/41 gearing give me around 65mph, so we will see how this turd holds up to that.

http://i206.photobucket.com/albums/b...p/DSCF3114.jpg

A little more progress. Made a top plate. Functions as a place to mount receiver, ESC, steering servo and as a chassis brace. Yes, that tan flat piece labeled "MM ESC" is the new MM Pro ESC; very very thin and is wireless! :lol:

http://scriptasylum.com/forumpics/4tec_5.jpg

Showing how the steering servo is mounted.

http://scriptasylum.com/forumpics/4tec_6.jpg

This one shows where the UBEC is gonna go. I removed the middle section from a servo case and screwed the bottom plate directly to the top part. Should be perfect for a DimensionEngineering ParkBEC (little one). The enlarged hole is for cooling.

http://scriptasylum.com/forumpics/4tec_7.jpg

This is turning out to be a "kit bash", lol:

- Wing stay from a Mugen MBX5 serves as a standoff for the brace.
- Turnbuckle from a Jato serves as the brace itself.
- Steering link and servo mounts from an XRay XT8 serving as intended.

Next up is the battery tray, which I'm still doing some thinking on...

Fun
 

Looks like your both having some fun with this. I have been thinking about picking up a 4tech for a while now. I would love to fun something on road, but the nitro stuff really stinks if you ask me to. The conversion looks to be quite a challenge though. How is it going now? I am looking forward to seeing your finished projects and some videos on how well they run for you. Good luck with that.

Looking good Brian. I am not sure if i will bother to brace the top of the chassis or not... Considering my batt tray is in the center it might be difficult to add any sort of brace. Hopefully the chassis is strong enough with the bent sides...

I do like the wireless esc, it was about time someone did something with all of those wires. I made a cordless toaster once, wanted it to be bathroom safe, just in case it fell in the tub.

Jerry: This isn't the best platform for conversions to be sure, but it is fun doing something challenging. And judging my Linc's and my conversion, we are going about it totally differently.

Linc: I also wasn't gonna worry much about bracing the chassis until I saw how much it flexed just by pushing down on the middle belt (to check tension). With the way I have it, there is VERY little flex. Probably wouldn't be needed since it is onroad, but I like to over-engineer stuff. Call it a weakness.

I am in the process of making the battery tray now. I'm just gonna use the same design as I used on my CRT.5 (v2). Seems to work well, and is pretty easy to make.

FYI: these progress pics are not the final product! I'm still going to paint stuff, trim protruding screws, etc. It's gotta be pretty!

Ok who is setting up a drag race between you to...may be hard to do, however, you both could find someone who has a radar gun and post results to see who has bragging rites!

Linc would probably win in a race as I'm only shooting for ~55-60mph. Just for playing around at the house on some deserted streets.

I am going to push mine and see what happens. Just had a drift session on the shop floor and after about 20mins of goofing off the motor was at 130, esc at 110 and batt at 100. I have a feeling I will be able to gear it up a bit. Also fixed the poor startup, upped the expo on the throttle channel to 50% forwards and reverse. Nice startup now, very little glitching. Pity the old bk does not have a lvc... I do have a li-saver, do they work on 5s?

I may be able to run a longer turnbuckle from the front to rear on both sides of the battery tray. That should add some rigidity.

I do have a radar gun, and plan to post results. I kinda think it is funny having a tc with a l can motor in it. Should be even funnier if the 1512 makes its way in there on 6s...

lol, it's not brushless yet, but since I don't plan on making any purchases in the very near future, I decided to slap the electronics from the Slash (XL-5, 12T titan, 6 NiMH cells). Obviously, it's pretty slow, but fine for in the house.

http://scriptasylum.com/forumpics/4tec_8.jpg

http://scriptasylum.com/forumpics/4tec_9.jpg

Here's where I ran into a problem. I wanted about 1/2"-3/4" chassis clearance to avoid the normal pebbles on the road. So, I modded the rear shock positions to get the back end higher. Then. to get the body to fit right, I had to lower the mounts. Unfortunately, the front upper shock mounts now got in the way, so I made a little cutout so they stick up out of the hood. Not the prettiest thing, but it works.

http://scriptasylum.com/forumpics/4tec_10.jpg

Since the Titan is so wide, I can only gear down to 15T, and it gets pretty warm - even warms the entire chassis! Oh well, the XL-5 and Titan are throw-away parts anyway. :smile:

Looks good Brian.

Cannot wait.
 

I personally cannot wait to see some videos of this thing once you get some brushless in there and some really good Lipo cells. I have kind of wondered about the 4tech as a BL road-racer for a while now. Your opening the door for guys like me, so thanks BG. It is going to be great to see the BL version up against one of the nitro cars. Good luck with your project Brian.

Hmm, I'm kinda torn right now.

I have enough spare parts to make a complete setup, but using a brushed motor (Titan 550 12T) but the belt arrangement creates a lot of drag. So, I was thinking of making this RWD only and keeping the Titan and XL5 ESC in there. Removing the front diff, shafts, belts, etc will make it quite a bit lighter and runtime will be better. 2WD will be harder to control, but the brushed motor doesn't have tons of torque anyway, so it shouldn't be too bad. This was never meant for a speed car anyway, so that's not a biggie.

If I went BL, I'm gonna have to wait for a motor.

I decided to go the 2WD route. Right away, I noticed it is faster and not any harder to control (at least in the basement). And the motor and ESC don't get as hot as fast. I think I'm gonna keep it this way. Fun for around the yard. If I want to go fast, I'll pull out the GTP...

i run a 12t titan on 4s a123 in a tt-01 with good results. it's slightly slower than the mm 8s fiego on 3s a123. just have to not over gear. the titan pushes a staduim truck to 30mph on 6 nimh cells. its a good bahsing setup

Yeah, it seems to go pretty good, considering.

Since the Titan on 4s A123 is roughly the same speed as an 8s on 3s A123, that means the kv of the Titan is around 3100. So, since I'm running 6 NiMH cells geared 45/15 in the 4-tec, that puts my top speed right around 32mph. Not high for an on-road car, and certainly a lot slower than stock, but fun for around the house bashing.

The only thing I don't like about the XL5 ESC is the piss poor brakes (and I did recalibrate the ESC to the radio). Having little experience with brushed motors, I don't know if this is the ESC's or the motor's fault. I may just throw in a spare MM/BEC setup so I can get better programming, and the ability to run 6 cells or 3s. Just gotta set it to brushed mode. Plus, if I decide to get a BL motor in the future, it'll be plug-n-play for the most part.

I run a pair of the 12t motors in a tamiya blackfoot, with front and rear trannys. I use a novak super duty on 3s lipo and it is geared for about 34-35mph. The rear motor does get warmer than the front, but I use a clip on heatsink to equalize the temps a bit. I have to run the motors without the slide on can wrap metal thingys (technical term, sorry about that for the noobs) as they are a tight fit in the trannys.

Great setup, and the novak esc has great brakes. It will do wheel stands in either direction. and I can run a low rate lipo, 18c 3000 (maybe not that low) and get 1/2 hour runtimes at least. I like the 12t motors, work well for me.

Yeah, I think the Titan will work fine for what I'm looking for. For me, high speeds=high repair bill. :oops:

But, changing over to 2WD is the best thing I could have done. Not only is it lighter and a LOT less drag, but I now have a spare diff and axles for the rear. :smile:

I tried to run mine 2wd... Wow, it was insane. The setup I run seems to need 4wd. As for the axles and diffs, they are holding up fine for me. I really doubt they will wear out quickly, but it is always good to have spares. I bet you removed a fair amount of weight doing that, 2 belts, the diff, front transfer shaft, driveshafts, etc. It all adds up.

What body do you plan to run?