Slash 4x4 Buggy 1717 6s
 

Hi, wanted to show you guys my Slash 4x4 Buggy conversion with a Castle 1717 on 6s.

It is basically finished now but I still need to find a good suspension setup.

- LCG Chassis dyed black
- Removed anodizing on colored parts
- Stock A-Arms with XO-1 hub carriers etc.
- Stampede front bumper
- selfmade front wing
- selfmade center shaft from 10mm CFK tube, 10% lighter than stock
- Stampede wheeliebar with alloy/rubber wheels
- Diffs and CVDs from XO-1
- RR Gen3 Slipper for Revo 3.3 38t
- selfmade motor plate
- selfmade "braceplate" which bolts the complete backend together
- selfmade CFK chassis brace
- TT ST-1 spoiler mount modified
- Stormracer spoiler (small and light)
- XO-1 wheels belted
- GRP 1/8 GT wheels belted
- VP Pro Buggy wheels belted
- Castle 1717 1650KV from XO-1
- Mamba Monster Extreme
- Traxxas TQI
- TT MT4 G3 stock Servo


Gearing with XO-1 tires: 22 pinion 38 spur, should give 95mph theoretically.
Gearing with GRP tires: 26 pinion 38 spur, should give 100mph theoretically.

Weight with XO-1 tires: 3.85kg ready to run with 5000mAh 6s 40C lipo.
Weight with GRP tires: 3.72kg ready to run with 5000mAh 6s 40C lipo.


Topspeed so far with GRP tires and 100mph gearing: 142kph or 88mph
Topspeed so far with XO-1 tires and 112mph gearing: 149kph or 93mph


Video:
http://youtu.be/GS3Os0yg6XA


http://i54.photobucket.com/albums/g1...ps9df7c77b.jpg

http://i54.photobucket.com/albums/g1...ps0e2e8f66.jpg


(click to enlarge)
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More pics (click to enlarge)

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I think I would remove the front bumper in exchange for a longer scoop - the scoop pushes the front down while the bumper pushes it back up. Cool slash for sure - there is a 120mph+ slash 4x4 in Detroit running 6s on a 2200 motor IIRC. Capable platform for sure.

Monster Mike: Yeah, it could use a little more downforce in the front, I will change that.


Got a Mobius action cam, really nice camera. Good quality, but small and not expensive.

Here is a on-board clip (watch to the end :mdr:)
http://youtu.be/0Df_XganRlU

Little update:

The selfmade CFK centershaft did not hold up, it broke. Strange thing is, that it happened during normal driving, no crash or something.
Have replaced it now with a stock centershaft, seems to hold up now with the chassis brace.

Then I made a new front wing from an 1/8th buggy wing and removed the Stampede Bumper. Doesn't look too good IMHO, but I think it makes more downforce.

Apart from that no defects or issues or crashes, it just runs. What I really like about the Slash drivetrain is that there are no drivecups (like on 1/8th scale buggys) that tend to wear down and are pricey and work intensive when they need replacement. Only part that wears down is the centershaft, but that is cheap and easy to replace.


Also found the reason for the bad straight line stability, it was the old servo I took from a TT MT4G3 which didn't center precisely anymore. Replaced it with a TT DS1015, much better now. Also experimented with toe-in on the frontwheels, which worsened steering so now I'm back to 0 degrees. Maybe I'll try
a little toe-out sometime to see what happens then.

Mounted a sway bar kit, seems to make a difference, the car rolls less now, but I guess I need some thicker wire to accomodate for the increased weight in comparison to a stock Slash.

The GRP S3 tires make nice traction but don't last too long, after about 10 packs they were almost done. But I must say I let the tires spin a lot.
Funny detail: Found two dead flies inside the rims, seems like they have been sucked-in somehow.

Body is now airtight from the underside, made some foam-thingies out of a touring-car bumper and also put some foam to the sides of the chassis to seal everything.

Put the mobius cam on the rear shocktower, but didn't turn out good, videos are too shakey, need to mount it firmer somehow.



As I am getting more practice, I begin to feel really safe while driving it, I can make 20 80+ mph passes in a row without breaking a sweat, in my opinion it is superior to the XO-1 in any way apart from looks. Better acceleration, better braking, and the most important thing, it's actually driveable and controllable on non-perfect roads. Even when it looses traction it's still controllable. And I can go through a full pack without heat issues.

The braking distance is really short, under 100feet from 90mph.

RTR weight with GRP tires as on the photos (but without cam) is 3572g now.




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Looking good. Tires are just like you describe - the better traction they provide, the faster they wear out. Regarding front toe - zero degrees is pretty ideal. Generally speaking, toe-in generates better initial steering off power, but tends to push more coming out of the turn(on power). Toe-out is essentially the opposite, providing less initial steering entering off power, but much better steering on power. Of course many other things in the setup affect steering.
Rear toe-out is almost unheard of, as it generally created instability. Rear toe does create some scrub, but adds straight line stability(pretty important for high speed). If the rest of the setup is pretty rigid(minimal flex and play in the linkage, etc.), I like 1-2 degrees rear toe for high speed straight line work(3 degrees is the norm for off-road).

Definitely must be a capable platform.

Some serious power you have there on your Slash. I'm amazed.

Little update:


As it turned out, the earlier 93mph run with the XO-1 tires (geared to 112mph with 26/38) was not valid, seems like the tool I used calculated the values on it's own based on the location and timestamps and did not use the speedstamps.

Made a new measurement, this time with the GRP tires (100mph theoretically with 26/38) and reached 94mph. The XO-1 needs a 121mph gearing to reach 100mph, which means, the Motor is less loaded in the Slash. Would be interesting to see what speeds the Slash can go to with 121mph gearing, I would guess something between 105 and 110mph.


Also made some acceleration tests, it accelerates from zero to 90mph in about 4 seconds and needs about 300ft of space to do this :mdr:

Now I'm thinking about putting something bigger in. What do you guys think, would a TP Power or Leopard 58x82 1420KV motor on 7s work with an XL2?


Topspeed 151kph / 94mph
http://i54.photobucket.com/albums/g1...psc720a4cd.jpg


Acceleration to 146kph / 90mph in 4 seconds:
http://i54.photobucket.com/albums/g1...ps38be4aaa.jpg



I think that was the effect I was having, it seemed more stable as long as you wouldn't touch the wheel, but when trying to correct a little, it would always be either no turn, or too much turn, which led to zigzag lines.

On the rear I have 3.5 degrees toe-in if I remember correctly, but I think the rear hub carriers can be swapped around to get 1.5 degrees, will try that sometime.

There is still play in the linkage and in the wheel carriers, need to find a way to reduce that.


Dafni:
Thanks, I'm amazed too how well this thing turned out :)

Little update.

Got a GPS speedometer and a sports radar for speed measurement so that I don't need to strap my phone to it anymore.
Mounted the cam on the rear shocktower and the speedo on the front shocktower so that it is visible in the video. Problem with the shocktower mount position is that it is very shaky, need to find a way to dampen it somehow.

Also found a closed road for driving without cars or people around. Very nice. What was not nice that I almost hit a rabbit that decided to cross the road just in front of my car. That would have been quite a mess :)



Then I crashed for the first time, wanted to chase my buddys 1:1 car and didn't realize he was braking, thought he would go WOT down the road, but he didn't :( Car went under his car and then my right rear tire got overrun by his rear tire. Well, his tire won.

Fronstpoiler mount broken, speedometer broken, cam broken, bulkhead broken, rear axle carrier bent, rear wheel broken, shock-cap ripped off.
For being run over by a 1:1 scale car not too bad. What really sucks is that the cam and the speedometer broke. Searched for the SDCard from the camera for half an hour and eventually found it, but unfortunately the video didn't get saved anymore, so no footage of the crash.

Repaired the car and added aluminium shock caps and camber links. Also dyed the shocks and springs black, now they don't look like cheap RTR shocks anymore :) Changed shock oil to 60 front / 50 rear, now it needs some testing if that is better than the 70/60 before.


Checked the front diff ring and pinion gear and inspected the driveshafts. Looks good, almost no wear on the front diff and the driveshafts look like brand new. The rubber boots with grease inside seem to do their job.

All 8 wheel bearings needed replacement, they were not running smooth anymore and two were really hard to turn.


Also received some 32 shore Johns BSR Buggy Dirt Oval Foam tires and an STRC alloy steering but haven't tried them yet. The BSR tires look like quality tires. Hope I made the right choice with the 32 hardness. Weight of the BSR tires is exactly the same as the GRP 1/8 GT tires, 350g for the complete set. Diameter is 105mm.



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My experience is that full size cars pretty much always win when matched in a crash to an RC car(particularly 1/10 size)! Really though...not a bad result considering the potential carnage.

A few more changes to the car.


replaced the wheeliebar made from a Stampede bumper with one made from an XO-1 diffusor. The wheels are more to the back, wider and lower to make sure unintended wheelies at high speed don't end in a flip over.

Since I needed the rear wingmount for my twin truggy again and wrenching wasn't too convenient with that thing in the way, I decided to make my own wingmount that is attached directly to the top of the shocktower. It looks a little "Low-Tech", but works well and is very light compared to the classic buggy wing mount.


Car weighs 3554g now ready to run with GRP tires.



Then finally had the opportunity to run it again.

The Shock setup with 60 wt front and 50 wt rear seems to be better than the 70/60 before. Although I have the feeling, that when almost fully compressed, the oil is too light. Maybe I should try some linear rate springs.


Also tried the 32 shore BSR tires. Well, they did not make very much grip and generally seem a little too hard, i.e. they don't "soak up" little bumps in the roads, I could hear the motor spin up briefly sometimes. Did not dare to go topspeed, as the rear of the car would get squirrelly when trying to accelerate hard. Tires didn't warm up after some time like the GRPs do. Made a burnout until they started smelling and were really hot, but this made almost no difference in grip, just a tad better. I guess I have to try 25 or 30 shore, but not sure if I will do this since the GRPs are much cheaper and perform well for me. Also I am not sure, if the BSR like the camber change when the suspension is compressed, as they are completely flat.

What was funny though, that I could make 30 foot long lines on the asphalt with them :)

Apart from that, they seem to be quality tires, no chunks ripped out or something like that, held up perfectly.



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That is great to see some doing the speed stuff Lizard.
Hello everyone I poked my head in for a few.
I try to follow up on this a little more. Looks good to me so far. :D

Thanks. Will keep you guys updated.

It might take some time, but it will receive a motor upgrade in the future :happy:

The xl2 will definitely run the bigger motor you suggested.

Changing the rear toe in from 3.5 to 1.5 will free up a few miles per hour.

Have you pulled a data chart to see how many watts you are pulling at top speed? I imagine a CC 2200 motor could get you the same speed with the added benefit of less weight and more kv.

Will try that with the toe-in. I could just increase gearing, but this wouldn't allow for running through a full pack without heat issues anymore. I think with the 1515 this would be even worse, it's a lot smaller and lighter than the 1717.

The XL2 was my first choice also, it's reasonably priced, quite small and has a really nice set of features, especially the datalogging is very nice.

But after thoroughly investigating and getting a broken one (to get an idea about mechanical/cooling design) I found some problems with it:

- cogging
- poor electrical design, something with the FET drivers and too long PCB connections (User "Uber" on RCGroups found out), Castle solved that by having the FET driver manufacturer make special drivers only for Castle instead of fixing the design
- Castle doesn't seem to care about it, no firmware updates, no comments or mitigations on the cogging issue
- poor cooling design
- mechanical design unsuited for car usage with bumps, shocks, vibrations and dirt
- They still seem to go up in smoke from time to time with no apparent reason and seem to be more delicate in general


I have now ordered an Alienpowersystem 8S 250A sensored ESC and a TP5040L (58x82mm, 836g) 1260kv sensored motor.

Don't know if that one is more reliable but it was cheaper and shouldn't have cogging issues because of the sensor.


No data chart, don't have a data logger, but I have found this on another forum:
I'ts a HPI Firestrom with Poseidon 1717 2200kv Castle knock-off, gearing for 155mph and same weight as my Slash. Topspeed was 123mph.
300Amps would be about 6kilowatts. Assuming 90% efficiency (probably too high ...) this would mean 600W of heat that has to be dissipated somehow.

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