Twin Castle 1717 Truggy project

[Lizard]

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:




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are from FLMs extended Savage A-Arm kit, the cups on the pinion gears of the front/rear diffs are Nitro-Mods 56HRC originally made for the Savage.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

[RC-Monster Mike]

cool - always love a unique frankenstein rc project.

[Arct1k]

I think that will make it move ;)

[snellemin]

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

[Lizard]

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.

[JERRY2KONE]

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.

[Arct1k]

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.

[Lizard]

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.

[Arct1k]

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 :)

[A RC Dude]

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

[aqwut]

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.

[florianz]

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

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.

[Lizard]

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.

[Lizard]

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 :)

[JERRY2KONE]

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.