Advice needed on losi 8ight T conversion
 

Hello


I am new to the electric world so please excuse my ignorance. I am from the UK and I currently race a nitro 8ight and 8ight T. Lately I have been reading on forums about brushless conversions and I was wondering if anyone could offer advice on a setup. I have read through the sticky guides which were useful at giving me the basic idea but now I want to try and decide on what components I will need/want. What sort of price will a brushless setup with li-po batteries be? I would like a good setup that had strong acceleration and a top speed of around 40MPH would be good. Is the size of the pinion gear limited or is this just down to personal preference? Also how long would I expect to get from one charge as I would really need about 25 minutes. Lastly (for now :mdr: ) please could you tell me about how the braking system works and is there a way to keep the mechanical brakes? If so is it worth the extra effort? Sorry for all of the questions but I have a lot to learn before I can decide on the set-up that's right for me. Any advice would be really appricated.

Many thanks,

Kieran

I don't run 1/8th brushless yet but I'll try to put out what I think are the basics after having followed some of the threads here on buggy conversions.

How expensive= how high end (read reliable)

40MPH can be calculated on BrianG's speed calculator, you'll need to know gear ratio's tire sizes and other hard to find info, but once you have the info it's simple.

Pinion gear is both speed and load related, seems most "non racing" guys go for the best speed without overheating components. Load=heat

25 minutes will be dictated by the watts the motor is using vs. Mah of the lipo's. There is a thread here titled "what are your run times?" you could thumb through this thread to get general ideas for buggies similar to what you want to do.

Mechanical brake are the preferred method for 1/8th buggies as this keeps the load of braking off the motor. As I understand it you just "Y" the throttle cable and run one to the brake servo and the other to the ESC, there is something about turning off the brakes on the ESC (sorry, that means Electronic Speed Controller if you didn't know), I'm sure turning off the brakes will be dictated by whatever ESC you choose.

You can choose from a few brands of motor, Neu seem to be the best, Hacker is good to, Lehner is midrange, and Feigao is budget but acceptable.

ESC's seem to be a personal preference, some cooling mod's need to be done on certain ESC's... seems like Quark is the go-to but I'm not running HV (high voltage) so I'd go with whats popular. Mabey take note of what other buggies are using when you look at the run times thread.

Lipo's are another wide variety item. I've been wanting to step up to some Flightpower EVO30's as they look good and people say they use quality cells. MaxAmps has done me extremely well and their service rocks! (p.s. if you go MaxAmps use their 5000Mah packs)

So there, I've stirred the pot for you and others should be along to correct me shortly, that will net you some more info :) Good luck, welcome to the hobby, welcome to the forum. You will be tossing nitro motors in the trash pretty quick once you use brushless with lipo's.

Being in the UK might make the choice of motor/esc different. You might have different options that are more cost effective... what is cheap to us might be for you. For example, you might be able to run Mtroniks stuff cheap?

In general it won't be hard to get a nice conversion to run 25 minutes. Especially if you run a high-end motor. Lehner, Plettenberg, Neu...

A good lipo with at least 5000 mah will be enough if you don't go crazy on the motor choice. 40mph is pretty fast, so you might need 6000mah+

Firstly thank you both for the replies, I now have a much better idea on what I should be looking for. I checked that thread about run times but at the minute I am still a bit confused by this as some of the run times were 7 minutes and some were over 40 so I will have to try and look up the different setups.

This will be my spare 8T that I am converting so it will be for practise and I hope to also get some track time in with it. So is the pinion size dictated by the performance vs over heating rather than which pinion will fit? Also as I am in the UK and most of time it's cold will this mean I will not have to worry as much about overheating or does the ambient tempreture not have much influence? The other thing to do with this is how water proof / water resistant are brushless set-ups? I sometimes race in wet conditions so I was wondering if this will be a serious issue.

I filled in the speed calculator as accuratly as I could to go 45MPH and I think it reccomended the Neu 1521/1y/F brushless motor ( http://www.rc-monster.com/proddetail...15211yf&cat=20 ) . Are these good motors and what are they like on power drainage? If it will run the battery down quickly then I will need to comprimise between power and run time as 25 minutes is about what I will need (ideally 45 minutes as this would allow me to run a full raceday without having to recharge the batteries) .

I have also been looking on the rc-monster site for li-po's and the largest capacity individual battery I could find was this PolyQuest 4s 6000mah 20c Lipo, does anyone have any information about the quality of this battery? I was looking at the MaxAmps Lipoly 8000mah 2S2P 7.4V Pack and was wondering if I would be able to connect 2 packs together so I got 14.8V and 8000mah? If so how would I mount this in the truggy, would I need two battery trays?

The ESC is the part I am compleatly confused about. I cannot really tell the difference between the different ones other than the price. Please could you tell me what things I need to look out for so I can decide which one would suit my setup the best? If I plan on using the mechanical brakes and steering will this come off my main battery or would I be better to run this system independantly from a different reciever battery? I have been looking at BECs and have seen how some ESCs say they have built built in BECs but I am still not too sure about this.

I have been looking at the RC Monster Brushless Motor Mount - Losi 8 and saw that it says Requires modification of the stock radio tray. Now allows use of mechanical brakes if desired - must use front brake cam/actuator to actuate above spur gear. Servo for mechanical rear brake must be planned and gearing will have limitations when using mechanical brakes. Will this be difficult to set-up or will it be better than relying on the motor for brakes?

Lastly the other thing that has been on my mind is the charger required. At the minute I have a Pro-peak sigma charger ( http://www.ripmax.com/item.asp?itemid=O-IP2850 ). Will this be sufficient for the high power li-pos I would need? I read that some li-pos need a charger that can recognise the number of cells and I am not sure if my charger does this? When you charge a li-po you have to select the voltage so is this all I need?

Thanks again for the help and sorry for the amount of questions but there is a lot I need to learn before I buy a brushless set-up as it's expencive I want to make the right decision the first time.

Also I forgot to add in my previous post as the pound is very strong against the doller at the minute most RC parts are half price for me if I buy them from the US so I will probably be ordering my stuff from the USA.

Long story short, here's my suggestions:

ESC options:
Mamba Max (water resistant)
Mtroniks Truck (100% waterproof)
Quark 125b (not waterproofed.. may need some modding to run cool)

Motor options:
Neu 1515 1Y (might have a little cogging on the Mamba right now...)
Lehner 1940 8t (Nice... but does have odd size 4mm shaft)
Plettenberg Big Maxximum (Very good motor but expensive)
Cheap: Feigao 9XL

Basicly any combination of the above choices will work fine... and there are more choices too, like the MGM escs.

ESCs have built in BECs, but normally you should bypass it and use a separate BEC device. Very simple... just unplug the red wire on the rx plug.

You don't need to use mechanical brakes... but if you must, then Mike's motor mounts allow you to do that. You will have to find a spot to mount the brake servo and linkages. The stock radio tray is always modified or removed with a brushless conversion.

Batteries: For runtime... I like the 8000mah for a truggy. You can use a single pack (4s4p) or two packs (2s2p) hooked together in series... doesn't matter.

Your charger looks fine to me. Up to 5s lipo. Max charge rate is 5 amps so the 8000 will take a little longer to charge than a charger than can do higher.

With a Neu 1515 and 8000mah pack you will get runtime of 30+ minutes racing. Even following a lipo rules of not discharging below @ 20% of capacity, you could still get 30 min.

I can run 40+ minutes on an 8000, in my buggy with a lower kv 1512.

My $.02 on runtime: I have a converted 8ight-T with a 1515/1y and a Quark 125b. I use either 13/48 or 14/48 gearing depending on track length and difficulty/elevation change. The longest I have ever run on the 3700 packs I have is 10 minutes and 8 second before hitting the 3.0v cuttoff on the quark. That run was with the 14/48, the top end dialed back about 10% and semi-conservative throttle control. Recharging, the batteries accepted almost 3900mah. I would think that runtime, even with an 8000, would be somewhere under 25 minutes at race pace with that settup. Also, like other people stated, the Quark definitely requires a heatsink and does'nt like high air temps and humidity. 15 or 20 minutes in temps over 90 degrees really gets one hot!

The guys at my track that are running 4s 4900's (pretty much all of them are flightpower cells) in truggys can get 12 -15 minutes maximum. That's works out to 25 maximum off an 8000 mah pack. I run 5s to get the same power and I used 6400 mah in 26 minutes of racing, so I think I can get just over 30 minutes.
At a decent sized track geared for ~35mph I wouldn't expect to get 30 minutes from an 8000mah pack, unless you spend 5 of those minutes upside down.

I use a neu 1515 2.5D and an unmoded quark 125. The night I did 26 minutes of racing was nice and cool, so I the temps on my esc and motor were under 100f. The week before that we were doing 5 minute races in the middle of a 100f day. I didn't get temps, but the motor and esc were getting quite hot. No thermals though. Once it start getting dark and cooled down a bit, the motor and esc temps dropped to just being warm after the race, so ambient temp seems to make a big difference. Same gearing, tires and setup were used, and at the same track.

Hey Glass, I'm gonna build an 8 buggy pretty soon and I'm curious as to what your gearing is with the 1900kv 1512. And just to verify, it is on 4s, correct?

14/46 is a good match for nitros on 4s... 16/46 if I want to really have fun on the track.

Runtime: I have not run my truggy for a while and never did a lot of data testing with it.

So I'm basing runtime estimates off of a buggy... must be a bigger gap there than I'm figuring. I get 20 minutes on a 4800 pack in my buggy outside and 25 minutes on my indoor track. This is during actual racing. I must not be driving as ballz-out as some of you guys.

Just my 2 cents

I have an 8ight-t with the 1515 1y, 16 tooth pinion, 5000 mah Neu 4S lipo with the Quark 125b. It is crazy fast, silky smooth, and I can get about 20-25 minutes bashing. I know racing uses more juice than bashing but if you are thinking 8000mah batteries you should be fine for 30 minutes.

With mike's or anyone elses motor mount you cannot use mechanical brakes since the motor is mounted where the throttle/ brake servo used to be. Here is an in-process picture:

<img src="http://i46.photobucket.com/albums/f129/dadgummit/DSC03653Medium.jpg">