[Racing t]

hi guys, I am about to getting and RC18t and I have the mamba system already (was for my MLST and decided not to use it) and I have a couple of questions, oh is a 6800kv BTW.

1. how fast it will go with the 6800kv and stock pack?
2. will I ruin the diffs because of the mamba?
3. what gearing is the best for a balance speed/aceleration.
4. what parts do i need to get for my rc18t to handle the mamba?
5. it will be too much to run 7-cell?
thax

[Quinton]

racing t - I run the 8000 in my FT rc18t. If you don't have the FT then you will need to install spacers in your diffs. Other then that you don't need to upgrade anything. I would get the RPM front bumper though - not needed for the Mamba, but it's kinda "needed" for any rc18 IMO.
I run gp1100 7 cell without any problems. Biggest problem is trying to keep the little light stable and not try to take flight. (buy gp1100 batts, makes a HUGE difference)

[Quinton]

Here's my nitro killer. lol

[End Overend]

Well, I've added a few new pieces to my RC18MT. It didn't take too long, it's only been what, two weeks...

The latest is an Integy steering link and a Trinity aluminum chassis. I really like the chassis, much sitffer, a little heavier, but nicely constructed.

Here are some pics...

[End Overend]

I also added an Integy steering link that really helps with the steering. I tried a DP Drag link, but it didn't fit well and ran into the top brace binding up the steering. I'll stick with the Integy since there is no binding and works very well.

[Quinton]

Sweet

[End Overend]

One more pic of the bottom of the chassis...

This will probably be the last addition to the truck for a while since I like the way it's set up now. I did put in an extra spacer in the diffs (3 total) which seems to have eliminated the gear slipping in the differentials.

The only other thing I'd like to add is some Lunsford Ti turnbuckels, but I can wait until these break.

Now I just need to get it on a track to see how it does. Maybe in a week or two.

[Racing t]

Originally Posted by Quinton

racing t - I run the 8000 in my FT rc18t. If you don't have the FT then you will need to install spacers in your diffs. Other then that you don't need to upgrade anything. I would get the RPM front bumper though - not needed for the Mamba, but it's kinda "needed" for any rc18 IMO.
I run gp1100 7 cell without any problems. Biggest problem is trying to keep the little light stable and not try to take flight. (buy gp1100 batts, makes a HUGE difference)

thanks quinton! I think I am getting the FT since I alredy have the motor and esc (mamba), the FT come with those spacers?.

BTW: would the mamba run better on the rc18mt? it is faster because of the size of the tires?

[End Overend]

Originally Posted by Racing t

thanks quinton! I think I am getting the FT since I alredy have the motor and esc (mamba), the FT come with those spacers?.

BTW: would the mamba run better on the rc18mt? it is faster because of the size of the tires?

The FT should come with spacers for the diffs, but I'd pick up an extra set to go with the kit. I found that I needed 3 spacers instead of the 2 that are in the kit to eliminate the gear slipping.

The mamba should run the same with either truck. You change the pinion size to compensate for the size difference in tires. Stock gearing on the MT is 10 tooth pinion and 60 tooth spur. On the FT you would jump to a 13 or 14 tooth pinion to go with the 60T spur. However, the FT might be a bit quicker since there would be less rotating weight for the motor to spin up, not much, but it might make a small difference.

[wheeleze]

Originally Posted by End Overend

The latest is an Integy steering link and a Trinity aluminum chassis. I really like the chassis, much sitffer, a little heavier, but nicely constructed.

Do you have a problem with the steering ball cups hitting the diff case? I cannot seem to get my steering link to fit. I've found shorter ball studs, but they are 4.2mm and bind on the 4mm cups.

[End Overend]

Wheeleze,

I don't have any problems with the diff case, but did have a problem with the servo holder. The rear mounted screw hit the front of the servo holder. A little dremel work solved that problem and I have full steering left and right.

[johnstoys]

Originally Posted by End Overend

I also added an Integy steering link that really helps with the steering. I tried a DP Drag link, but it didn't fit well and ran into the top brace binding up the steering. I'll stick with the Integy since there is no binding and works very well.

Very nice job -- looks great.

Interesting about the steering links as I've been looking at the DP product -- may have to consider going the Integy route. Man, the steering slop on the 18Ts is terrible -- probably my biggest complaint about them out of the box.

[Quinton]

Racing t - Mine started out as the FT kit and my friends started out as the rc18MT. 10 minutes later and there is no difference in them. lol The MT tires suck on pavement in our opinion. I would go with whichever one you prefer.

Here's my friends. He's in the process of adding quite abit of aluminum to it. I prefer less weight and the forgiving plastic in crashes. I painted the body for him.

[End Overend]

Originally Posted by johnstoys

Interesting about the steering links as I've been looking at the DP product -- may have to consider going the Integy route. Man, the steering slop on the 18Ts is terrible -- probably my biggest complaint about them out of the box.

The DP link seems to be hit or miss. I had to pull out the dremel and sand down the top just to get it to work, and even then it was still binding. Others seem to have great luck with it.

Also with the Integy, some people have had the ball cups hit the differential case, mine however have plenty of clearance. I did have a problem with the back servo side screw hitting the servo holder. Again I had to dremel a little, but the end result is much better than stock and it doesn't have the binding that the DP link did.

I do however agree that the steering slop is the biggest complaint I had about the RC18T in it's stock form. Second to that was the chassis flex. With the changes I've made I've got no complaints about the little truck now.

[Racing t]

thaks for the replies guys, one more question can I install the hitec HS-81 on my RC18t ft?

Quinton: your friend has a nice ride, cool paint jod I like it very much!

[Quinton]

The hitec 81 will fit. I have one I'm not using if you're interested. I'm using the 56.

[Racing t]

thanks, but will I need any mods to make it fit?

[wheeleze]

Originally Posted by Racing t

thanks, but will I need any mods to make it fit?

The 56 will bolt in using the optional servo mounts, but you'll have to glue the 81 down. You won't need to mod anything more than how thick the shoe glue is so your servo arm doesn't hit the chassis. You may have to sand/cut the servo case a little to get full right throw.

[jmcn r]

i have seen a few people cut 4 holes in the chassis and use small zip ties to get an extra strong strap down when you go for the over sized hitecs. i plan to do that myself.


guys i am still in a bit of a bind here....i do not think i quite get the workings of Lipo cells and how they match up to a regular Nimh. i have 3 packs of the reedy Mini max cells for my 18 FT. I have a Mamba 8k as i was thinking of parking lots runs with the 18 at first. now it seems i may actually use it offroad so i may step to a Mamba 68k instead.

what type of Lipo cell am i going to have to use to match the 6 cell gp 1100 in terms of punch to satisfy the Mamba? i am just a bit confused by Lipo ratings.





oh...and does anybidy know if any of the chassis kits out there will accept the big Hitec servos as a drop in?

thanks in advance.

[Honda Aero]

Originally Posted by jmcn r

guys i am still in a bit of a bind here....i do not think i quite get the workings of Lipo cells and how they match up to a regular Nimh. i have 3 packs of the reedy Mini max cells for my 18 FT. I have a Mamba 8k as i was thinking of parking lots runs with the 18 at first. now it seems i may actually use it offroad so i may step to a Mamba 68k instead.

what type of Lipo cell am i going to have to use to match the 6 cell gp 1100 in terms of punch to satisfy the Mamba? i am just a bit confused by Lipo ratings.

If you are going to use the truck off road and you are going to use Lipo's, I'd actually suggest you step down to the 5400 instead of the 6800. With a 7.4v (2s) Lipo and the 5400 you will still reach speeds in the 30 mph range, which for this little truck is plenty fast enough off road.

The simple fact is you will not find a Lipo that gives the equivilant punch of your 6 cell Reedy's. It's either going to be more or less than your current Reedy's (and only less if you go with a 1s Lipo (3.7v) which really won't run with trucks.

The reason you will get a lot more punch out of a 7.4v Lipo when compared to a 7.2v NiMh is because of the lower internal resistance of the Lipo and the fact that they carry a higher average voltage than the NiMh's for the duration of the pack. The lower internal resistance allows the Lipos to deliver their power much more effeciently than a NiMh or NiCad, which gives a lot more punch to Brushless motors. The Lipo also tends to run in the low 8v to high 7v range through most of the batteries capacity, which again helps with power.

Overall, stick to 7.4v (2s) Lipos unless you are doing insane speed runs on the road.

[johnstoys]

Not trashing the Hitec servos by any means (I know their rep), but if you're interested in an upgrade from stock, the Airtronics Micro (94091Z) is a good alternative and is a direct drop-in to the 18T. No messing around to make it fit.

http://www2.towerhobbies.com/cgi-bin...?&I=LXWC40&P=0

[jmcn r]

Originally Posted by Honda Aero

If you are going to use the truck off road and you are going to use Lipo's, I'd actually suggest you step down to the 5400 instead of the 6800. With a 7.4v (2s) Lipo and the 5400 you will still reach speeds in the 30 mph range, which for this little truck is plenty fast enough off road.

The simple fact is you will not find a Lipo that gives the equivilant punch of your 6 cell Reedy's. It's either going to be more or less than your current Reedy's (and only less if you go with a 1s Lipo (3.7v) which really won't run with trucks.

The reason you will get a lot more punch out of a 7.4v Lipo when compared to a 7.2v NiMh is because of the lower internal resistance of the Lipo and the fact that they carry a higher average voltage than the NiMh's for the duration of the pack. The lower internal resistance allows the Lipos to deliver their power much more effeciently than a NiMh or NiCad, which gives a lot more punch to Brushless motors. The Lipo also tends to run in the low 8v to high 7v range through most of the batteries capacity, which again helps with power.

Overall, stick to 7.4v (2s) Lipos unless you are doing insane speed runs on the road.

thats for the super quick response!
I do need the extra speed for what im look at. my perspective has changed to an outdoor offroad track. i will run the 18FT for fun but unless they listen to me and create an alternate route that cuts off the straight for 1/18 scale (alot of people want to bring minis with them torun) it is going to mean i am running down the samelong straight as my LSP and Savage. i do need the extra speed and power.

i am out for the convenience of lipo...they just seem to be alot easier to have in the long run. just want to give them a shot to know if i should have been afraid of them all this time or are they exactly what i am looking for.
2s 7.4v huh? hmmmm.....now i atleast get how they match up. i didn't before.

[Honda Aero]

jmcn r,

Here are some numbers for you for the Mamba Motors and a comparison for 6 cell to 2 cell Lipos and 3 cell Lipos. These are taken off of Castle Creations web site.

5400:

6 Cell NiMh: 20 mph
2s Lipos: 33 mph
3s Lipos: 40 mph

6800:

6 Cell NiMh: 27 mph
2s Lipos: 40 mph
3s Lipos: 50 mph

The problem you are going to run into running them on dirt is that they tend to bounce around more and more the faster you go. Running on the same track as 1/10 scale trucks and MT's the track will likely not be that well groomed. Too much speed can actually be detrimental to the ability of the 1/18th scale trucks. A 2s Lipo with the 6800 is going to put you around 40 mph, which means it's going to bounce around a lot. To the point it may not be controllable at those speeds.

However a 2s Lipo with the 5400 running at 33 mph will be more controllable. Also how much speed are you really going to need? On most tracks the top speed of the bigger cars tends to be in the low 30's, even on big tracks. Remember, most of the time when it comes to racing: Slow is fast.

The 5400 will be much more effecient and will give longer run times, with lower amp bursts compared to the 6800, which will be easier on the Lipos.

Also consider parts breakage. The jump between the 5400 and the 6800 seems to be a big line for parts breakage. The 6800 puts out a lot more power and seems to be much harder on the drivetrain than the 5400.

I know at the local track here they recomend the 5400 over the 6800 for driveablity reasons. The 6800 is just to much for the track and it makes for a very difficult car to handle.

Anyway, just something to think about.

[jmcn r]

thanks again for all the food for thought Aero. much appreciated.

i am totally ignorant to some of the ratings and measurements i have been reading time and time again. when rating Lipo cells, what does the "S" number mean? such as 11S, 12 S etc. C obviously refers to cell count correct? also...what on earth is amp burst exactly? i have always assumed the burst refers to the "hit" from the motor higher being less linear. wild geuss though.

are there any good links around the place explaining some of that in detail?



again when it comes to speed, i will have to put some extra thought into as i have had your thoughts all along thats why i am considering going down to 6800. from my experiences so far with high powered mini's in my driveway as an example. they accelerate to their top speed so quick i usually have space left before i need to start decelerating again. I am also going over to 1/10th TC wheels and rally tyres to try and combat some of the low end "over power"...how much do you think that would help aero? also the track surface is pretty stable. some big left-right uppsetters, but they are large enough that they should practically be like a hill for the 1/18th.

still not enthusiatic about going offroad with the 18t.....

if i start to worry too much about the 18s competence offroadafter i raise the power bar up too much i am afraid i will scrap the idea and go hyperion/mlst and save the 18 for the driveway duties.

thanks for the help so far aero. lol.....i knew i shoiuld have saved that link that had all the info on lipos from when i first saw it over a year ago. lipo looked so scary to me then i didnt look back.

[Honda Aero]

jmcn r,


The "S" is for the number of cells in series. 1 cell = 1s= 3.7v, the more cells the higher the voltage. When you get to bigger batteries you will see a "P" added to the numbers. That's how many have been added in parallel to increase the capacity of the battery.

So for example a 3000 mAh 2s2p battery would be 2 cells in series and 2 cells in parallel. Essentially it would be 2 1500 mAh 3.7v cells put in parallel to get the 3000 mAh, then run in series with 2 more 1500 mAh 3.7v cells to give you a 3000 mAh 7.4v battery pack.

C referes to it's discharge abilities. Take a 3000 mAh battery that's 20C. That's 3 amp hours worth of power that can be discharged at 20x's that amount in a continous rating. So a 3000 mAh battery with 20c discharge rating can run continously with a 60 amp draw. The burst rating is generally how much it can handle for 30 seconds. So it might have a 30C burst rating or 90 amp discharge for 30 seconds. Those are it's maximum safe discharge ratings for the battery.

This is where you need to know the rating of the motor you are using. If your motor uses more continous amps or has a higher burst rating than your batteries you run the risk of blowing them up or having them swell (a precurser to blowing up).

As far as running off road, don't forget about a loss of traction off road. Too much power and you spin your wheels, which many times will result in a spin out and a loss of time. This is where "Slow is Fast", because if you don't have the traction to instantly accelerate, you can't do it. The reality is when you go off road, even on a good track you need to de-tune your motor.

That's the nice thing about the Mamba controller, especially with the Castle Link. You can tune your little truck for the track conditions and de-tune your motors or the acceleration for better control.

Chances are, with a properly set up 18T you will be surprise at how well it will do on the track. If it's smooth, keep your damping a little slower for bigger jumps. If you find it bouncing around a lot, lighten the damping.

Also a little more weight will actually help the 18T on a track and off road. Some some aluminum bits will actually make the little truck more stable. Just make sure they are in the correct areas.

I suppose in the end you could go with the 6800 and de-tune it for the track, but even then it might be a bit more than you are expecting on a track.