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Losi 8ight-T & TP4070 (40x102mm) motor
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Dr_T
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Losi 8ight-T & TP4070 (40x102mm) motor - 10.14.2014, 04:20 PM

Hi,

Newly registered here and thought I'd show you my 8ight-T 2.0/3.0 cross-over running a TP Power TP4070 motor. Current set-up:
  • Losi brushless conversion kit;
  • Turnigy Heavy Duty Series 5Ah 6S 60C-120C batteries;
  • Hobbywing Xerun 150A ESC + 2x1000uf 35V Panasonic FC caps;
  • TP Power TP4070-1200kv 3.5Y, 40x102mm motor with DIY low-tech 8->5mm shaft reduction;
  • 8T 3.0 ring and pinion gears (12/47 ratio instead of 10/43);
  • Turnigy TGY-DS2509MG servo @ 8.4V (rebranded KST DS2509MG);
  • Turnigy TR302-AD Gyro – I know… training wheels, and real men don’t use stability augmentation… they race toy cars on 2S or 4S, right?
  • LOSB3528 Heavy-Duty Differential Cases;
  • Diff oil: 20k/2.000k/10k cSt;
  • 3.8 Badland Tires wrapped with (32kg) fishline, as I suck at taping and gluing tires;
  • Gearing: 23/43 for 63 mph nominal (3.7V/cell), zero-timing, no-load wheelspeed; off-road use, mainly grass.

Arrived at the TP4070 after trying out a Leopard 4082-1600 and Alien Power Systems 4092-1380. Both of which I could not keep temps under control with 45-50 mph gearing. Wanted a big motor to be able to run higher loads at lower temps, but didn't want to spend Neu 1527 money, and the TP4070 seemed to be the closest thing for about 1/2 the price. I have a Castle 1717-1650 on the way to compare to the TP4070. Also very interested in seeing results of the recently released Poseidon 1527-1500 car motor.

The TP motor isn't bad at all and I'm still practicing not to crash everytime I try and open up the throttle. Motor temps typically stay on the good side of 65C driving hard for a full pack, unless doing crazy high RPM doughnuts in grass for a while, in which case I have seen motor temps of a little over 70C; I guess everything has its limits. Center diff typically stays below 60C with some 2.000.000 cSt diff fluid I tried from Lizard. Ran around 110C and 85C with 130k and 500k respectively.

I am looking to replace the Xerun ESC sooner or later. It is ok and holding up well, but I'm missing the ability to set a Current limit. I'm running the 6S 5.0Ah 60-120C Turnigy HD batteries and even with fully charged packs an uncareful throttle blib can trigger my external Lipo alarm, indicating Voltage sag to 3.3V in at least one of the cells. Limiting Current to say 200 Amps max would probably not be noticeable in performance (I won't be able to put down 4+ kW anyway), but it will make life on the batteries a bit easier. Also eventually I would like to up the Voltage to 8S, as 6S might not be the most efficient on the 1200kv TP motor. Let's hope Castle's XL3(?) will be announced soon and turns out to be designed as a true car ESC with a footprint that can be used in 1/8 too.

Vids or it didn't happen:

Early test set-up:


Badlands without fishline:


Little street test:


Fishlined Badlands:


Tredecuple-flip cartwheel - personal best so far:


Some pics:


















Last edited by Dr_T; 10.15.2014 at 03:27 PM. Reason: forgot a comma
   
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targetingxmod
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10.18.2014, 12:27 PM

How is the fishline holding up in those Badlands?

And when 1717 arrives report back runtimes with a 5000mah 6s lipo! I may have to look in there for the truggy... now since the 4070 have gotten to another place!

One more thing.. don't you have sparks when plug that? I have to make an anti-spark plug or else i am gonna fry very shortly. My lipo's are so verocius, i guess!

Last edited by targetingxmod; 10.18.2014 at 12:30 PM.
   
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Dr_T
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10.20.2014, 02:24 PM

So far, so good. I think the fishline will hold for some time as I only drive in grass with the Badlands and the tire lugs are fairly big, reducing contact between the fishline and surface.

No anti-spark here; don't know if that's really necessary, I figured I would just swap the connectors it they get too burnt up :D.
   
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10.24.2014, 05:10 PM

GPS-ed my 96 km/h geared set-up today at 121 km/h! Don't know if it's all caused by ballooning and some timing (ran 7), but it was a pleasant surprise. I know 120 km/h is child's-play compared to hardcore speeders, but remember: my set-up is intended for off-road, and I can run this exact set-up, with even bigger tires, hard on grass without re-gearing. Great thing is, the 54C motor temp (15C ambient) is at the end of a full 5.0 Ah pack doing those speeds! Also runtime is much better than on grass, I think I got about 15 min per 5.0 Ah pack.

After running 2.5 packs I obviously got overconfident and wanted to do some show-boating wheelies at 100+ km/h... which I messed up... Well, nothing a little sand paper and a can of flat clear Tamiya spray can't fix. GPS is a bit bruised too, but luckily still works.

I could use some advise on my suspension, as that currently sucks a bit. I read in the HUDY car set-up guide that the spring preloaders should be used to lower ride height, instead of the droop screws, so I did. But I guess my springs or shock oil are way too soft as it all is a bit "floaty". Check the vid for what I mean.

Should I run stiffer springs or heavier shock oil for street use? I have purple springs in the rear and grey in the front and HPI 35wt oil front and rear. Any tips on how to tune my suspension for street are greatly appreciated!

















   
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11.05.2014, 08:29 AM

It turns out my TP4070-1200 motor is actually a ~1500kv, instead of 1200kv, which means I've been running 128 km/h (79 mph) gearing on Badland tires through grass all along. Explains the higher than expected speeds I logged earlier and also why it was so hard to get to full throttle off-road without ending up in everlasting cartwheels. Did a quick no-load bench test with an Eagletree logger for different timing settings and these are the results:



Also got some running logs. Gearing in these logs is 23/43, 12/47 diffs and 133 mm OD tires, yielding 114 km/h nominal voltage, no-load, unballooned, zero-timing wheel speed (better be specific right?). Total weight is around 5300 g, wheel/tire weight 1044 g. I reduced front toe to 0 and rear toe-in from 3 to 2 (minimum with the adjustable 8T hinge pin brace) and got the front bumper off to reduce front lift. Unfortunately, the GPS logger has been a bit buggy after the last crash and keeps losing satellite lock, so I don't have good speed measurements, but given the RPM log and the amount of tire ballooning, speed should be in the order of 115-120 km/h again.

I made a high Current 8 awg bypass on the logger and re-calibration was done a bit quick and dirty with simple tools, so absolute accuracy of the Current readings is not guaranteed. Energy consumption based on cumulative mAh comes pretty close though, so it can't be too far off.



Combined datalog for 3 batteries (1st is Turnigy 40C 5.0Ah, 2nd and 3rd are the 60C 5.0Ah Turnigy HDs):



3rd battery Voltage, Power and Cumulative mAh; true runtime a little under 9 min until 3.5V LVC, with ~3.7V resting Voltage, putting through ~4.8Ah. Voltage sags 2-3V under heavy load, but not to the levels the Lipo alarm made me believe:



Zoomed in at three passes; forgot to log throttle input, but from the Current profile you can tell I'm building up throttle slowly; Current still goes up to 190-200A. I never tried smashing throttle to see resulting Current spike, as I hate painting... Also note how Current drops significantly once peak RPM (top speed) has been reached, as the Power component related to acceleration dies out then:





More pics to get to my 10 pic quotum :).







   
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Dr_T
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11.08.2014, 04:48 PM

New video:



Turned out my GPS was not broken after the crash at first test-drive, it just did not like to be mounted next to the Hobbyking wingcam. Somehow the camera causes enough EM interference for it to loose satellite lock... awesome feature for those using that camera on their planes I suppose.

Same gearing as last post: 23/43 (max Losi brushless mount), 12/47 diffs and 133 mm OD tires, yielding 114 km/h nominal voltage, no-load, unballooned, zero-timing wheel speed. Interesting findings:
  • With these tires and on this (less than optimal, but hey... it's a Truggy) surface, I can't seem to put much more than 4 kW of power on the road effectively. Trying to accelerate faster causes so much loss of traction I can't keep a straight track (as demonstrated in the vid).
  • Due to this limited acceleration, it takes about 7 s and 150 m to get to 120+ km/h - got to work on that, as that's some embarrassing performance :D.
  • On a fresh Turnigy 5.0Ah 60C battery, Voltage drops 3.6-2.8 V in the first couple of passes (below 22.2 V nominal Voltage), with the biggest drop at the first pass.
  • At 120-125 km/h load, RPM is around 30k; taking into account the Voltage sag, this is about 92% of the unloaded RPM.
  • After reaching peak RPM (top speed), the Power component used for acceleration dies out and Power supply drops to around 3 kW, which appears to be the amount required to sustain the 120-125 km/h speed for my car (sum of aerodynamics, rolling resistance, drive line friction, electric losses).
  • At top speed, the temperature of the sensor on the motor stabilizes, or even drops (I know this says nothing about the motor's internal temp, but I still think it's funny). Factors involved are likely the increased airflow, the drop in Power consumption at steady state and running closer to peak efficiency RPM than while accelerating.




Total 3 packs of 5.0Ah


Zoomed in at 5 interesting passes


Combine speed profile


Single battery speed profile

Last edited by Dr_T; 11.08.2014 at 04:50 PM.
   
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03.07.2015, 05:40 PM

Little update:
  • ~7 lbs/inch Durango springs;
  • 800 cSt shock oil;
  • Diffs 70k-2000k-40k cSt (f-c-r);
  • 1/5 TC GRP tires;
  • 27/35 gearing with Fly Ratio spur.
















Last edited by Dr_T; 03.07.2015 at 05:44 PM.
   
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03.07.2015, 05:42 PM

...and some preliminary datalogs...

Geared 27/35, for a no-load wheel-speed of 146 kph (91 mph). Was a quicky, so no videos yet unfortunately... only had time for one pack. I didn't drive it in a long time and space was a bit limited, so I only dared to bring it up to a GPS recorded 109 kph (68 mph), which it would do within 3 seconds and within a distance of 50 m from standstill. Was fun to be out with it again :). To record a good top-speed with the 1 Hz GPS logger I need some more space and confidence. Might try to find a cheap Eagle-tree GPS sensor, as those log with 10 Hz.

I changed too much at the same time (diff fluids, shock oil, spring rate and tires), to be able to pin-point what did what, but I really like how it drives now, seems "sharper" and more controllable than before. Front wing is not finished yet, but at the speeds I did today, the front did not seem to lift.

The 1/5 TC GRP tires are a huge step up from the normal 1/8 truck tires, a lot of grip and car can accelerate quite quick now, found some pieces in the logs the car went from 25kph to 84kph in 1 second. That's an acceleration of 16 m/s^2, ~1.6 g, so 1.6 times faster than Mother Earth would accelerate it if being dropped from the rooftop :D. That comes with a lot of violence though, I was really impressed to see and hear the car working that hard, and the datalogs do scare me a bit - biggest recorded peak was 336 A, which made the 5Ah 60C Turnigy HD battery drop to 3.28 V/Cell. You can see in the logs it takes the batteriy about 7 seconds to recuperate from such a hit...











   
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ruudxd
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03.10.2015, 06:16 PM

Looks great!
How do you like the FG tires?
They look a bit hard?
And how did you secure the fishline around your tires?
Is there a specific good knot?
   
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Dr_T
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03.11.2015, 06:10 PM

Thanks Ruud!

Tires are GRPs. The rubber is way firmer and less "gummy"-like than regular RC tires, but somehow it's way more sticky too. Only used them once so far now, but I like them and can recommend them if you like speeding.

The knot in the fish line is just a normal knot, sealed with CA glue so it won't come loose.
   
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ruudxd
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03.12.2015, 08:56 AM

Ah, that CA glue is a good trick!
I suck at making knots, I can just ty my shoes :)
I never had FG style onroad tires, or tires like that, but they look a lot firmer indeed.
I have some roadrages now, so if they break it would be cool to try the FG style tires!
   
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florianz
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06.02.2015, 06:15 PM

Hi,

I love that build, looks awesome. That long TP looks cool, too. I am glad that these motors are becoming more popular. I have a smaller 36-74 sized 2000kv motor, which worked very well: copper from front to end, long rotor magnet. The other one is a TP-V2-4050L-7D, with 1750kv, where I still search for the right timing and settings, as I miss a bit of power. Overall quality is much better then with the Leopard motors, and I like them more then the Tenshock.

You should try out a torsen differential in the center, like that you don't have use such heavy silicone oil, you get about 80 % of the power to the rear differential.
Unfortunately, the ofna/hobao torsen diffs (the other brand name I have forgotten) are a bit hard to find. A while ago some torsens were available at the LRP shop.
The losi smart diff did not hold up well and doesn't lock that hard like a torsen.

that trick with the fish line is great, I have to try that out! Hate taping tires too. Do you have kinda long time experience with it?

To avoid the voltage sag, you can put two (smaller) lipo packs in series, means extra weight, but more available energy as well.

Excellent!!

florian
   
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Dr_T
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06.08.2015, 05:41 PM

Hi Florianz, thanks for the compliment and advice!

Cool info on the Torsen diffs, never heard of them, sounds very interesting. You use them? What would be the advantage over a thick fluid conventional diff you think?

I found the fishline thing in some old 2007 Traxxas thread if I remember correctly, seemed like a forgotten old-school trick. I only have 9 packs (through grass/dirt) on the fishlines and the line does show some wear as you can see in the pic below (mainly on the rears; fronts have less wear, so rotating front/rears occasionally will help prolonging life of the lines). One of the advantages over tape though is that it is not that much of an issue if the lines wear out, as the lines are very easy to make and replace. In fact, you could make some spares to take with you, so down-time would be minimal if a line would snap (which will eventually happen).

I see you're from HH, me too! Where do you drive? I'm still looking for a good place to do some fast on-road driving :).

   
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florianz
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06.14.2015, 06:57 AM

Hi Dr. T,

I am driving offroad at the track in Bergedorf, but I have heard that there is an on-road track in HH-Boberg (never have been there).

I used to have a Torsen in my former Truggys and buggys (brushless), it just works like a real 1:1 Torsen. There are differend LSD-Limited Slip Diffs around, the Losi SD, the XRAY Active Diff, the Kyosho diff, Torsen, the BBF's, Fioroni etd. The one I have is a Hobao/ofna Torsen for hyper 7. about 10yrs ago they have been popular, and where available for Hobao Hyper Cars for example.
AFAIK Walter Rhrls Audi Quattro had Torsen Differentials:
https://en.wikipedia.org/wiki/Quattr...l-drive_system)

I used it in center, it kind of locks the diff, most of the power gets to the rear when I pull the trigger. I loved it. But you have to get used to it, the rear might get nervous, an you don't have a "pulling" front wheel. Locking can be very sudden.
I have this one, found mine on egay usa years ago:
http://www.rcmart.com/ofna-87326-tor...er-p-9113.html

I am now running a Losi Smart Diff in Center, the Torsen doesn't fit in my current truggy. It has a less locking function then the torsen unfortunately, but in total better then a normal Diff with 60k fluid. Locks less then the regular 60k diff, but corners very well.
The Losi SD require more maintenance then the torsen. I used the Torsen in two cars, the worm gears are like new, one outdrive has shows some wear.
As you can read, I am really a big fan of torsen

How long is your center diff in total?

I will check out that fishing line trick!
best regards
flo
   
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06.16.2015, 10:51 AM

Cool, I'm not a racer though. I'm from Altona, enough parks for off-road bashing around me. On-road speed stuff is a bit more difficult, there's some streets near Volkspark and HSV Stadium that are ok, but looking for a bit more space. I think the Dom might work too, but could be tricky trying not to run into drunken people :D.

My diff is 24 mm bearing (flange) to bearing. So far the 2000k cSt in the Losi HD LST diffs is working very well. For high frequency load differences it pretty much acts as a spool, but there's still enough give for slower load changes.
   
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