Twin Castle 1717 Truggy project
 

Hello everybody,

since I still wasn't satisfied with the performance of my 1717 powered Truggy I looked at different options on how to drastically increase power.

After ruling out 1/5 scale components and high voltages for several reasons (more expensive, not as reliable, bad weight distribution, 8mm mod1 pinions hard to get and pricey),
this is how far I've gotten until now:


http://i54.photobucket.com/albums/g1...ps2945c02f.jpg

Wheelbase is about 42cm, length from Bumper to bumper is about 62cm. The body will be a Associated Rival body. A wing is still missing, but I will probably fit one later.
Final weight will be around 7.5Kg, weight distribution front/rear will be about 49%/51%, left/right weight distribution will differ less than 0.5%.

Tires in the picture are belted FG 1/6 scale Buggy onroad slicks on Carson 1/6 scale Buggy rims. Diameter is about the same as Truggy wheels but they are a little narrower.


Chassis is constructed by bolting a cut TT MT4 G3 and a cut TT EB4 chassis together, this gives about 55mm more length to fit all the components.

The two Mamba Monster ESCs will sit on the middle section above the center diff and will be wired to two paralleled 6s 5000maH 40C lipos.
The angles that you see in the middle section are not cut to length yet, they will be connected to an undertray that will make the chassis about 15mm wider and will also form the sideguards.
Receiver and BEC will go in front of the left motor right next to the steering servo.

Front Diffbox is from a Inferno MP7.5, rear diffbox is GPM alloy for a Savage (to allow for CEN diffs). Bumpers are also from a Savage. The rest of the parts are from a TT ST-1 Pro.

Front/center/rear diffs are taken from a CEN Genesis GST 7.7, center dogbones are from FLMs extended Savage A-Arm kit, the cups on the pinion gears of the front/rear diffs are Nitro-Mods 56HRC originally made for the Savage.

Driveshafts to the wheels are stock, but with a Torx setscrew and high strength threadlock to stop the pins from coming lose.

I hope I can run 21/46 gearing which should give 100mph topspeed and wheelies at 60+ mph :diablo:

cool - always love a unique frankenstein rc project.

I think that will make it move ;)

Holy.....Twin 1717. I love this custom build.

Thanks for your comments. Glad that you like it :)

Made a little progress:

Mounted four extra shocks because I did not want to go through the hassle of finding (much) harder springs for the shocks and thought it might be more durable and even load distribution on the a-arms is also a plus with that much weight on them I guess. Oil is 40wt all around, not sure if that is good, but I will leave it for now. Had to relocate the body-mounts because of the additional shocks, so an old Savage shocktower and bodymounts got re-used.

Received the Rival body and test-mounted it, I think with the body on it looks too narrow, I need to try +5mm offset squares and see how it looks then.

Found two different sets (28 and 40 shore) of some very rare Prafa 1/5 foam tires in 133mm diameter. Hope they will be good for speedruns. Does anybody know how to properly glue them to the rims?

Also made some more pictures. For size comparison: The Savage is 30mm extended and has a stock MT4 G3 body on it.

The motors are bolted to 8mm 7075 motor plates with four M4 countersunk screws. Centerdiff mounts are two MT4 G3 motormounts with the motormount-part cut off. The plate under the chassis is 3mm 7075.
I don't really like how the upper front hinge-pin brace is mounted, but I couldn't find a better way. Hope that it will hold up.

http://i54.photobucket.com/albums/g1...ps7ed471c7.jpghttp://i54.photobucket.com/albums/g1...ps5695fcaa.jpghttp://i54.photobucket.com/albums/g1...ps41772b80.jpghttp://i54.photobucket.com/albums/g1...ps4af2e0d6.jpghttp://i54.photobucket.com/albums/g1...ps716279ba.jpg
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Interesting
 

Your setup looks interesting enough, and you are on the right track if you want more power. It looks like you have done the easy part of this project. now you have to find a way to sync the electronics on this to make them work in harmony with each other. that should be fun. Like stated above this kind of one off project is always a curious build to watch, because we have not seen this setup before.

Not knocking this build in any way - it's going to be a best. However this style if setup is no different than a dual brushless eMaxx of old.

No special syncing is needed unless you want to run off the same esc. Even this is possible (not advisable at all) by syncing the phases to the motors. If you search way way back (6 years lol) there are instructions on how to do it.

Yes, others have done it before.
There is a guy on Traxxas Forums with a twin 1717 XO-1 with MGM Compro ESCs on 8S that is claiming to have reached over 150mph.
There is also a guy on Savage Central forums with a twin Castle 1515 + Mamba Monster ESCs Savage who reached over 90mph with it, so I'm pretty convinced that it will work for me also.

To make sure everything runs nice and in sync, I have exactly the same motor+ESC combo (from XO-1) that will be connected to the receiver via a Y-cable. Settings on each ESC will be exactly the same and batteries plus nine 470uF extra capacitors will be connected in parallel, so that both ESCs draw power from the same capacitors and battery. Cables will be kept as short as possible.

To prevent one ESC from shutting off before the other (maybe due to small measurement differences) I plan to set low voltage cut-off to something around 3.3V or 3.4V on the ESCs and use another external LiPo buzzer set to 3.5V or something.

For extra cooling I plan on removing the ESC plastic housing and putting bigger 30x30x15 (stock is 30x30x7) fans on them that are always-on.

Internal BECs will be disabled and fans on the ESCs will be powered by an external BEC so the ESCs do not need to cope with things other than powering the motors.

Extra caps and external BEC will help a lot. I doubt you need to mess with all the fans.

Looks like you have everything covered. Build on fast - enjoying watching this one :)

Very nice build! Can't wait to see a video of course lol

Looks good dude. Dual brushless setups always look so good. I would recommend turning off the low voltage cut-off. Maybe a low voltage alarm. But, no cut-off, just in one decide to cut off before the other. Otherwise, keep us posted. I feel sorry for the diffs with this powerful setup.

this is awesome... twin 1717... damn!:whip:

What I really like are these custom things like these different diff housings, different tires etc. must have taken some time to get all the experiments done.

I remember a project on offroad-cult.org where ron2 did a similar project with two 3680 medusa, w. two ESC i think.

small update:

Have googled for pics of Mamba Monster ESCs and found out that there are more ESCs without solder on the underside of the motor connectors, so I guess this is normal.

Both ESCs and also the lipos are plasti-dipped now.

The planned mounting position of the ESCs (on top of the center diff) turned out to be not very good because they would sit quite high and also the plate ontop of the center diff would have been quite large to fit two ESCs plus capacitors. Also didn't like my initial plan of replacing the 30x30x7 fans with 30x30x10 fans, those small fans are just too wimpy IMHO, a small leaf can make them stop turning. Could put a grill over them (tried that actually), but then they make even less airflow.
So the ESCs will probably be placed next to the motors for lower center of gravity and cooling using the fans that cool the motors. Only concern is that the motor heat will transfer to the ESCs, but I think with a strong 60x60 fan over each motor/ESC that should not be a big problem.

Also got some new on and offroad tires and rims.

Onroads are belted MCD Rally x4 142mm ROSSA TARMAC Blue Spot.
Weight will be around 280g mounted, 20g lighter than my FG onroad slicks, very nice.

Offroads are Elcon Astro Turf medium, weight will be around 300g mounted, not light, but still okay.

Rims are MCD Half-disc rim black with 24mm hex and aluminum re-inforcement ring around the hex.

http://i54.photobucket.com/albums/g1...ps1d86695e.jpghttp://i54.photobucket.com/albums/g1...psc50f4d4c.jpghttp://i54.photobucket.com/albums/g1...ps14d5505d.jpghttp://i54.photobucket.com/albums/g1...ps7fc3b9d6.jpghttp://i54.photobucket.com/albums/g1...psc74cb339.jpg

Was busy working on my 1717 6s Slash 4x4 and didn't have much motivation lately to work on the twin, but now a little update.

Cut down the motor plates so that the top plate sits lower and made a top plate for the diff/motormounts from 3mm CFK. Did not turn out very nice as I was too impatient, but it should serve it's purpose.

florianz: Found the project with the two Medusa Motors from RON2. Looks much more nicely done than my project. But my project is clearly ahead when it comes to power/weight ratio :)


http://i54.photobucket.com/albums/g1...ps60c9edbf.jpg

Lawn mulcher
 

This thing looks like it is going to be a real lawn mulcher of a vehicle with that much power to control. One 1717 motor is already enough to deal with, and two of them will surely make a fun day. Good luck getting this put together and looking forward to seeing your testing experiences.

Can't wait to see videos of this thing if you ever film it. Going be some kind of monster, that's for sure.

A little progress.


Mounted a wing and a wheeliebar using the ST-1 Pro wingmount. Somehow I don't like the look of these high-downforce wings, need to search for something with a more "classic" look.

Wheeliebar is from an MT4G3, it's compatible with the ST-1 Pro wingmount and fits niceley through the Savage bumper.

Painted and trimmed the body. With only 185g it's quite light for the size. As it already worked well with my Slash, securing of the body to the chassis will be done using velcro.

Then I finally started making the chassis tray, took me a while to decide on material and how to make it. Material is HDPE, it's light, slippery, strong and can be welded using a heatgun. Now the complete underside except for the (flush) aluminum plate in the middle is covered with plastic. Next step is to weld 2 inch high sidewalls to the plastic bottom plate to make it a tray.



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Keep going! What a MONSTER!:lol::intello::party::yipi:

Manne:
Yeah, my trigger finger is already itching, hope I'll get it running before the weather gets too bad :)


Chassis Tray is done and seems to be pretty solid. Welding the PE with the heatgun turned out to be not too hard. It doesn't look too good, but considering that this was my first time welding something, I'm happy. Should keep the dirt out and protect everything on the chassis.

Made a chassis brace from 10mm CFK tube that connects to the front and rear diffhousings/bulkheads. The rear plastic block on the brace also acts as a brace for the wingmount.

Front and center diff are now shimmed and filled. Front 30.000 cst, center 2.000.000. Since I did the rear diff half a year ago, I don't remember what I filled in, I think it's 20.000 or 30.000 :)



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I love the looks of carbonfiber, but I have never used it on any of my trucks, maybe it´s time to use it on my new truck.

What cases are those that the cen diff sits in?

Those are GPM cases for the old (non-X) Savage. Last time I have used them was 2007 on my Nitro Savage.

Should be plenty of power, Truck looks great.

Thanks :) Yeah, I hope that thing will rip seriously.


Now it's nearing finished state.

Chassis tray and chassis brace are now on the car. Then made another brace using Savage hinge-pin braces from the wingmount to the aluminum profile in the rear. Chassis seems very stiff now. Batteries are strapped to the chassis with two big straps that go between the chassis-tray and the chassis-plate.


Wired up the ESCs and plastidipped everything. Wiring is not really clean, will do this later. As a switch I used an 8-pin socket/plug, this switches both ESCs, the BEC and the 24V on simultaneously. For testing purposes I made two extra plugs that allow to switch on the ESCs seperately.

The BEC is a 7A 5.5V Hobbyking BEC, Servo is Savox SA-1283SG with 300Ncm at 6V. Without extra capacitor, there are glitches when moving the servo fast, with capacitor it seems to be okay.

Wires are all 0,5qmm silicone wires and the plus and minus rails on the Traxxas TQI receiver habe been re-inforced with copper and solder to make sure the servo gets enough power.

As you can see, the ESCs are now right next to the motors, this way they can be cooled by the same 80mm 24V fans that cool the motors.


RTR Weight as on the picture with 225g PMT 1/5 scale GT tires is quite exactly 8kg or 17.6lbs.
Theoretical topspeed is 78mph now with 3.7V per cell, 4.72 inch tires, 46/20 gears and 2.888 CEN diffs.

The Mamba Monster startup beep sequence is "polyphonic" now, sounds cool :)
Did a quick testrun in my home on tiles. It cogged a little. Gave it more throttle, now I have some black rubber marks on my tiles. Feels really powerful already. Need to test it outside.



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Yay, it's running :)


Went through two battery sets, no crashes or damages so far. Did not dare to go full throttle, because it was pulling to the side when accelerating hard, need to check if everything is setup 100% exact.

The PMT 1/5 scale GT tires worked quite well with the 8Kg car, far better than with my 5.4Kg 1717 Truggy, although I think it's not perfect yet. Could not get them warmer than 35 Celsius. Maybe I should try the GRP 1/5 scale tires, they are said to be less dependent on temperature.

Handling is quite good for my taste, but the steering is sloppy, the plastic servo mount flexes too much, need to make a more rigid mount.

The motor ran good, with gearing for 125kph maximum temp was about 40C (with 20C ambient temp). ESCs and batteries were even below that temp.

Sound is also very nice for my taste, quite loud for an electric-powered car :)


Here is a short video of the first run:
[youtube]tnB3zRuVEeE[/youtube]


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That's one of the coolest thing's I have seen in a long time. The sound of that is awesome with it being that loud. How do you like the HobbyKing BEC?

Thanks :)

The Hobbyking BEC seems to work fine. Only thing that's strange is, that I needed a glitchbuster capacitor, I would have thought that external BECs don't need this. On the other hand, Savox servos are known to draw lots of current and the Servo is very strong, so maybe it's normal (?).

Looks good!
Keep messing around and you be flying in no time. :D

Finally ran it again and made a video :)
Will post more info later.

[YOUTUBE]wmRFF8hRKhc[/YOUTUBE]

Very cool. That thing really moves!

Looks quick! plenty of power on tap..

Yep. That's a proper powered truggy.. Topspeed could be higher, considering the setup?

Yeah, I need to gear it up more I guess. I first geared it down because the cogging was a little annoying. Somehow, startup seems harder to do for the ESC although there are two motors. Will need to play with startup power and maybe change the throttle curve some more.

Here is another video:

[YOUTUBE]9eAmY-sT7H4[/YOUTUBE]




It's starting to collect dead flies :mdr:

http://i54.photobucket.com/albums/g1...psxx74by5m.jpg

Did some drifting on the weekend, was a lot of fun. Controlled 360ies work with about a 50% throttle blip, 720ies with about 75% throttle. With full throttle it gets so violent that the car leaves the ground :)

[youtube]lQli_eD1xFw[/youtube]

Power is just silly.. I love it!

Definitely one of my favorite builds. Great job, Lizard!

Thanks, glad that you guys like it :)