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  1. #1
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    Rustler/Bandit Mid Motor Laydown Conversion

    Hey everyone! I wanted to share a new project I've been working on. It's based on the Slash conversion I did last year but it's got some improvements based on things I learned on that last project.

    This time around I wanted to make something for the Rustler/Bandit platform. Stadium trucks are my first RC love and buggies are where it's at in the racing scene so it made perfect sense to see what I could do with this platform.

    There were a couple of things about my Slash conversion I really didn't like. The L braces I used to mount the top brace to the chassis were a pain in the rear to manufacture and they let the car flex a bit too much up front. This time around I'm ditching them in favor of some beefy aluminum stand-offs that I can just buy right off of mcmaster-carr. I've also tweaked the side stiffeners so they are more "in-line" with the top brace.

    The next major issue I wanted to address was getting the transmission case back in it's stock location. I had to move the transmission case 1/2" forward on the Slash to prevent the spur gear from interfering with the shock tower. It mostly worked, though I still had to modify the shock tower, but it also put the drive shafts at a pretty extreme angle which I just didn't like. My solution this time was to ditch the stock shock tower and redesign it so it's narrower at the base. I also designed a camber mounting plate that puts the camber links further back and prevents them from interfering with anything.

    I've been working on this project for a few weeks already but I just machined the new chassis parts today. Check it out, it's already looking awesome!

    My biggest decision I still need to make is if I should turn it into a Rustler or a Bandit. I love stadium trucks, but I'd also want to take a buggy to my local astroturf track to race. hmmm....




  2. #2
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    I was looking at this earlier. Impressive prototyping.
    Can’t wait to see more

  3. #3
    RC Qualifier FlyingTigerDad's Avatar
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    I enjoyed the Slash build that you did earlier quite a bit, so I'm definitely looking forward to seeing how this turns out. Your engineering/fabrication skills are top notch, and these builds come out very professional looking. The Slash was an excellent performer as recall too.

    I'm sure you'll get the kinks worked out, and any weaknesses you perceive corrected for another quality build. And as much as I'd like to see this come out as a stadium truck (they're kind of my thing too), I do think you'll probably get much more use out of it as buggy. It's just (unfortunately for guys like me) a much more popular racing class.
    Last edited by FlyingTigerDad; 11-04-2019 at 05:52 PM.
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  4. #4
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    Done!

    I had the day off so I used it to machine the rest of the parts for this build and swap everything over from my slash.

    I decided to make a rustler out of this build mainly because I just didn't want to have to buy new arms/links/drive shaft. The only thing I really need now is some ST wheels/tires and a rustler body. For body I'm thinking the jconcepts f150 because it reminds me so much of my old T3. Speaking of the old T3, I borrowed the body to get an idea of how it's going to look finished!



    Under the body - the electronics are jammed in pretty tight up front but they just barely fit.


    This new transmission case design puts the drive shafts back in line with the arms.


    Custom camber link plate


    And my favorite part - NO MORE HARD TO MAKE L-BRACES!


    While putting this together I wrote down everything that was "wrong" - things like bearing fitment inside the transmission being too tight or moving hole placements and diameters on the chassis. Unfortunately there were issues from the previous design that I never wrote down or fixed.

    I've also got a few ideas for things I want to change. The shock tower definitely should be made out of something thicker/stiffer and the shape needs to be tweaked a bit as well.

    Overall I'm pretty pleased with this design. The place that does the 3d printing had a new minimum order price that they didn't have last year so I ended up ordering three of the transmissions cases so I'm thinking I may still end up building myself a bandit

  5. #5
    RC Qualifier FlyingTigerDad's Avatar
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    As I suspected - another fine job. The truck looks great and I imagine will be a great performer as well, especially with some of the design improvements you mentioned (drive shafts in-line with the arms, etc.). Glad you went with the stadium truck setup. I like the JConcepts F-150 idea for the body too, it will look great on there - very T3 like indeed. Looking forward to a track report
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  6. #6
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    Thanks FTD! I'm more excited about getting this on the track than I ever was about my Slash. Stadium trucks just drive so much better than SCTs and I can't wait to see what this can do.

    When I raced my slash I really got a kick out of driving the pink RTR body. It's just not what you'd expect to see on a car setting fast laps. I think the JC F-150 gives the rustler that old school 90's look that would be equally unexpected - it would be the next best thing to the original rustler body which is what I'd absolutely love to have.

  7. #7
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    Alright, so I just pulled the trigger on the JC F-150 body. I'm excited for that to get here... not so excited to paint it.

    Anyway, I was moving around some stuff in my RC area and stumbled on my old 22 3.0 chassis. I thought it would be interesting to do a quick comparison between a (nearly) modern race chassis and my rustler.

    This first shot shows the 22 3.0 in it's original mid motor configuration with the battery the whole way back. The battery and motor are much farther back on the 22 than the rustler.


    While it wasn't originally an option on the car, there were aftermarket laydown kits you could get for the 22 3.0. The picture below shows where the battery and motor would have been in that configuration. It's pretty interesting to see that it's just about right in line with my rustler design.


    Anyway, I never realized how drastic the difference was between a regular mid motor configuration and a laydown configuration. The laydown puts the two heaviest parts an inch closer to the center of the car which should drastically reduce it's moment of inertia when turning.

    On a final note, I took the car out for a quick bash session in front of the house. It drives so much better as a stadium truck even just bashing around on the street. I can't wait to hit the track with it!
    Last edited by rc10nick; 11-09-2019 at 06:13 PM.

  8. #8
    RC Champion zedorda's Avatar
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    How does it compare in weight to an original rustler?

  9. #9
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    Quote Originally Posted by zedorda View Post
    How does it compare in weight to an original rustler?
    I don't know how it compares to a stock rustler, but I did weigh it last night.

    The total weight with the T3 body, SCT wheels, and the electronics you see in my pics was 1790g with a 45:55 front:rear weight distribution.

  10. #10
    RC Champion zedorda's Avatar
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    Stock VXL 2wd Rustler without a battery is 1,690g. In case you were wondering.

  11. #11
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    Quote Originally Posted by zedorda View Post
    Stock VXL 2wd Rustler without a battery is 1,690g. In case you were wondering.
    Good to know! In that case my truck is lighter than stock by a good margin. My shorty pack is 215g which takes my truck down to 1575 without a battery. That's 115g less than stock!

  12. #12
    RC Champion zedorda's Avatar
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    By the looks of it you could if you wanted still shave off another 100g or more. But seems like a screamer already.

  13. #13
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    The JConcepts F-150 body is all painted and ready to go. At this point it looks too darn nice to even think about running it. I just need to figure out a way to rig up a body post for the rear and it's good to go. I thought the body would be narrow enough to Velcro to the side of the chassis but unfortunately that's not the case so now I need to improvise.


  14. #14
    RC Qualifier FlyingTigerDad's Avatar
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    The F-150 body came out nice & clean - it looks great! Ready to hit the track! Perhaps an Associated, or Losi rear truck body mount that attaches to the shock tower might work well. I'm sure you'll come up with something good & secure. Good luck & keep us posted on it's track performance. Will you be installing a sway bar setup at all?
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  15. #15
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    I figured out a less than elegant solution to the rear body post.



    And finally, here it is completely track ready (except the SCT wheels/tires, but it's close enough at this point to try it at the track).


  16. #16
    RC Qualifier FlyingTigerDad's Avatar
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    Quote Originally Posted by rc10nick View Post
    I figured out a less than elegant solution to the rear body post.



    And finally, here it is completely track ready (except the SCT wheels/tires, but it's close enough at this point to try it at the track).

    A good sturdy solution, even if not the most elegant - it works. Good luck on the track - I really want to see this truck do well.
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  17. #17
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    I got the car out on the track today! Unfortunately I didn't take any time to set it up so it drove like a dog. The biggest problem was how bouncy the thing was. Every time the car landed it would bounce around wildly. I'll need to address that before I take it out again. I also need to get a set of proper turf tires - my SCT mini pins just won't cut it.

    I only got about a pack and a half in before my rear shock tower broke. Going in I knew if anything was going to break it would be either the rear camber plate or the shock tower so I'm not entirely surprised. I used the same 3/32" G10 for the shock tower that I used for the chassis when really I should have used something thicker. I'll be getting a sheet of something thicker for the next one. I'll also machine in a body post so I don't have to have that ugly chopped up stock tower bolted to it.


  18. #18
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    I was getting ready to post an update pic with the new turf wheels/tires I bought when I noticed something - take a look at post #15 above. Notice anything in the first picture? One of the hex screws holding the tower into the transmission case stripped out when I did the test fit of all the new parts. I tried using my hacksaw to put a slot in the screw head (I was out of cut off wheels for the dremel so I improvised), but as you can see I ended up cutting into the shock tower instead. That's exactly where it broke - now I'm wondering if the shock tower would have been fine if I hadn't damaged it with the hacksaw. Something to think about...

    I still haven't gotten the thicker g10/fr4 in the mail yet, but I ran out to my LHS today to grab some turf tires for the truck. I got them mounted up this evening and they look pretty nice.

  19. #19
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    Fantastic

    Great build! I just did my first race in a 13.5 stock stadium truck class with my Rustler. Lets just say that I had my butt handed to me. Fastest lap to fastest lap I was at about a 2 second deficit. I'm sure my driving wasn't up to par, but overall I didn't have the handling to even hang onto the tail of the pack.

    Now onto your 3D printing stuff. I'd love to work with you on this. I do structural 3D printing and CAD design as a side business. I print in carbon fiber reinforced nylon and I'd really like to work with you on your gearbox.

    I plan to develop a few parts to make my Rustler a little more competitive as well. I had intended on getting a Losi or Associated, however I'm going to tinker a little more before giving up on the Rustler.

    Thanks,
    Andy

  20. #20
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    Thanks for the kind words! It's nice to hear from a pro that I'm not completely off track!

    As far as the design work goes I'm pretty much done. Everything at this point is error correction and refinement. I really don't have any further "big changes" in line for this project.

    I've got some more updates since my last post. I got the thicker g10/fr4 in the mail on Tuesday so when I got home from work that day I spent the evening cutting out new parts and working on the shocks.

    Here's the new thicker shock tower in black g10/fr4:


    I was a bit skeptical at first about the look of the black g10. This stuff is fairly glossy and I prefer a matte look, but once I cut parts out of it I realized it looked fine.

    I made two shock towers and two camber plates to I could have spares just in case I broke something again.

    You can also see in the picture part of what I did with the truck's setup. I took out about 6mm of droop all around and snapped this picture between doing the rear shocks so you could see how much that really is. I also lowered the ride height as much as I could.

    Last night was another practice night at the turf track. Between the new tires and the tuning I did to the truck I was able to shave an entire second off of my fast lap time - from 18.6 down to 17.6. Those lap times are competitive in stadium truck at that track but not the fastest. The real fast guys can get down into the 16s at that track with a truck. However, even at my peak when I was racing every weekend these guys were still a fair bit faster than me even when I was running modern high end kits so I'd say the gap in lap times are about equal to the talent gap that existed in the past.

    I do think I can gain more time through set up - the fast truck guys were all running sway bars so I'm going to have to add them to this car similar to how I did them on my previous build. The challenge will be adding a front sway-bar. The RPM arms don't have any extra holes for mounting sway bars so I'm going to have to get pretty creative.

    Finally, I wasn't able to run the truck the entire night. This time the steering bell crank on the truck broke. While it's at least validating that nothing I made broke, it's still frustrating when other parts break and end my night. This track isn't connected to a hobby shop and I don't have spare traxxas parts so anything that breaks pretty much ends my night.

  21. #21
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    Time for another quick update!

    I replaced my broken steering bellcrank with the black aluminum Hot Racing bellcrank. I thought about just getting another stock bellcrank, but I run a metal gear servo with no servo saver. If I bought another stock part it would likely break again. The HR bellcrank also has the benefit of being much more precise - there is far less slop in the steering now as compared to the stock bellcrank assembly.



    I also got to thinking about how I have adjustable camber link locations in the rear, but nothing for up front. I realized I was more than capable of addressing this issue and went to work designing and making my own front shock tower with maybe way too many camber link holes. Right now I have the front links installed in the spot that lines up with the original stock tower.


  22. #22
    RC Qualifier FlyingTigerDad's Avatar
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    I saw the nick (pun intended ) in the old rear shock tower, but wasn't sure if it was a shadow in the picture, a flaw in the fiberglass, or an actual cut in the material. Either way, the thicker black G-10 tower you came up with should work well as a long term solution (like the integrated rear body mount too).

    You should have pretty good luck with the HR steering rack as well. My son's 2WD Slash has that setup, and it's quite resilient.

    The front tower is a nice addition, but I agree with you, and think you may have gone a little overboard with Swiss cheese camber link mounting selections - about half those choices should cover just about any track condition setup.

    Very nice truck though, and yes, sway bars will get it absolutely planted on the carpet.
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