Preparing for 808 2009 spec conversion

[Nek]

Hey everyone be ready for a looong post I like to tackle my projects thoroughly...

I used to be into RC cars when I was a kid then went back to RC stuff a few years ago with helis. It had always been my dream when I was a kid. It was fun but big $$$ and damn hard I am now living in the south pacific so it's that much harder for me to get parts for that hobby. This led me back to RC cars as a few buddies here had some. The loop is closed I guess

So I got a rtr revo during a trip to the US. And since I was always very bad with nitro engines I broke it, so off to converting to electric These forums have been a great help to doing so, thanks a lot to all of you active, and not so active, members here!!!

Now that it's done I really want to convert a 1/8th buggy, always loved those! I plan to only race at the track with it so I started looking at the different top of the line kits and of course my choice ended up on the XRAY 808 2009 spec. What a great looking/engineered machine, I just can't wait to start building the kit!

All this to say that tools wise I am pretty unequiped lol So I need to make sure I will order all I need cause there are no LHS here I got the basic hand and hobby tools, but will need all the right oils, grease, setup tools and rc car specific stuff, cause my blade balancer and pitch meter wont be of much help

But first things first, what I plan on using to convert the kit and you guys opinion on that! Keep in mind that my motto is light is right, I really want to end up with the lightest possible buggy

Powerplant wise I was thinking about a Tekno Neu 1509 1.5Y F 2400kv. Seems like the Tekno version has a few perks that the regular one doesn't (http://www.teknorc.com/product_info....oducts_id=1009).
This motor sticks with the light theme, and from what I could read on it it would work very nicely in a light buggy.
ESC is a no brainer, MMM. Got one in my revo, love it! BUT the new Tekin RX8 looks pretty damn nice aswell but to take full advantage of it I need to use Tekin's sensored motor, and that means a heavier motor, not good.
I am running 4S in my revo and will stick to that. This is a track buggy, no need for insane power, and I have a few 3800 packs that are light as hell and will be great for short mains!
What size pinion should I use? I was thinking of RCM 5mm bore mod1 pinion 14/15/16T so I have some tweaking options, sounds good?

Now for the conversion in itself. The RCM 2 piece mount for the 808 looks so pimp, thanks for such a nice product Mike! I will keep the standard servo tray by cutting off only the steering part. (Ace R/C DS1015 is good for steering? Any better options? Overkill does not exist IMO haha).
The RCM battery tray looks like a winner for my project. I can mill it ALOT to make it lighter and have one that fits my lipos just right, custom sized.

Then there is the mounting of the RX and ESC. In the conversions I saw on this forum both guys put the ESC on a mount over the rear drive shaft. I'd rather have mine right on the chassis behind my battery tray, I'll try to have the tray as forward as possible, looks like the MMM will fit just right behind it. Any reason not to mount it on the chassis directly. No mount means less weight haha For the RX same thing, no RX box just the micro Spektrum RX right on the chassis. How could I protect it easily? Or should I even bother to, it's not like I will run it in puddles or under the rain!

In the future I want to add a slipperential and an active diff in the front. Does the slipperential drop right in with RCM motor mount?

For diff oil getting 3k/5k/7k xray oils should be good right? Any other weight I should get? For shocks 400/500/600 xray oil is good?

What are the setup tools I really need to get?

I think thats it

Thanks for any help on that project, looking forward to you guys input!

[rootar]

youll be happier with a 1512....

[Nek]

Well that's one of the points I am the most hesitant about

Anyone here had a 1509 in one of their buggy and found that it got hot or lacked torque?

I live in a pretty warm weather and really don't want to add fans on my ESC and motor, so yeah maybe the 1512 would work better

haaaa these options are killing me

[Arct1k]

PM Jhautz - He's most knowledgable on this setup.

[jhautz]

Hey man. Sounds like you have a decent plan going there. I'll agree with the guys that said to go with the 1512. I personally havent owned a 1509, but a good friend did and it was OK for the small indoor track, but once he hit the large outdoor with bigger straight, and bigger jumps it was a bit lacking on both power and ability to stay cool.

If you are serious about racing it and you live in awarm climate like you said i would seriuosly urge you to look at a higher voltage than 4s. you can get it done on 4s no question, but you will run lower temps and have a happier system with 5s. I have tried more different motors and voltages in my 808 than I care to admit (lots-o-money to try all them out) and what I finally settled on as the best all around setup for racing on a fairly large track was 5s and the 1512/1.5Y or 1512/3D. Both motors run outstanding on 5s and run nice and cool. you can easilly get 15 minutes on 5s 4350 and if you are only planning to run 10 minute mains you can even run some nice lightweight 5s 3200-300mah packs provided you get packs built with decent cells and they can handle the discharge duties.

And no... 5s doesnt mean more power over 4s, with the proper motor selection it means the same power but you generate the power with more volts and less amps which means ,esc, battery and motor are all happier (and cooler).

As far as the setup goes on the 808. I tried quite a few different setups as well and keep comming back to very close to the basic setup sheet that comes in the box. I would recomend starting there and making adjustments as you feel the need. The basic setup is a very fogiving and easy to diver setup. I actually run slightly heavier oils in the shocks (50-100pts heavier is all) and sometimes run the blue/grey springs in the front if I feel like the rear end is too loose. if you are looking for something a little more agressive go the the xray website and in the setup sheet section search for "Rocco" in the drivers name and look for his most recent "starting setup" sheet. Its also a good setup to start from, but a bit more agressive than the box setup.


Slipperential will take a littel work to fit in. I havent tried it yet in the 808, but the stock spur gear size on the 808 is 42T and the smallest spur on the slipperential is 46T, so its probably gonna take some spacers somewhere to get it all to fit and not rub on anything. I'm planning to do it soon, so when I do I'll be posting pictures and what I found needed to be done in the "where it works" thread in the slipperential forum.

The Active Diff in the front is a pretty cool option to have. It depends on the track layout. i feel like its has alot of upside if there is alot of sweeping on power turns in the track layout, but if its alot of hard breaking into sharp corners it actually can make it harder to drive. Its a tuning tool. Probably not something you just put in and leave in, but for certain situations its awesome. I havent had mine that long and am still trying to learn how to best use it to my advantage, and exactly when to use it.

[Nek]

wow thanks so much for all that info jhautz, you made my powerplant choice very clear now :)
So between the 1.5Y and the 3D which one will work better on a not so large track. Our straight is only about 25m/80ft, but there are lots of jumps! What pinion would you run?

I'll buy 2 new 5S packs then since I can also use them in my revo (and it seems like I should damn, guess I'll turn my 2S packs into 6S for the revo lol) is there a brand that is known to make lighter packs than others?

Just from browsing on RCM I found the Hyperion Litestorm 3300 5S that looks like pretty good packs if they are really light. Just to go for some fast laps for maybe 5 or so minutes those look killer: 2500mA 5S at 314g it's really light for a 5S but it better be with that little juice haha. Too bad there is no weight info for the Hyperion 3300.
And Hyperion also makes a 4350 pack, that would have me set lipo wise if those are indeed good and light cells as they advertise it.

jhautz, do you think I can fit an MMM on the chassis behind the battery tray if I use a 5S and Mike's tray? Maybe a Losi tray that has the ESC mount in the back would work nicely for what I want to do...

Thanks for the tips on the setup, I had a look in xray sheet database on their forums but there are sooo many of them.

You also cleared up what kind of track the front active diff works on and it's not the one I run on. Lots of 180 and 90 degree turns lol A good save on my wallet for that one haha

I'll start to put together a *new* list of stuff I need and will probably be back with more questions

btw I now hate excel for giving a total price at the bottom of my rc stuff lists... damn you maths!!! damn you!!! It's always: oh yeah 50 here, 120 there, 80 here,etc... and then

[jhautz]

2500mah seems really small to me. I wouldn't be worried about the run time if you were just going to run 5 minute qualifiers, but the current demend will be really tough on a pack that small. If you are looking to go small on the capacity due to short race lengths and you want a very light setup you are going to need to buy packs built with cells that have a very high discharge rating. I wouldnt personally even consider a 5s/2500mah pack in an 1/8 scale, and the 3300 would need to be built with cells rated for 30C continuous or better. Otherwise they may not last as long as you would like.

Yes you probably just fit the MM behind the battery tray. but its tight and I personally didnt like the way it handled with the battery weight that far forward. It made the back end too loose for my taste. I personally prefered it middle chassis which helped the back end feel more planted, but still allowed enough weight forward to get good turn in. I wound up with the speed controll over the rear driveshaft.

Tried fitting a losi tray at one point but it didnt work out to well. None of the holes really lined up with anything so the only way to mount it would have been to drill new holes in the chassis where the battery tray holes were. Mikes battery box is simple and works well IMO.

[Nek]

I think I found the lipos I needed :)
Fast laps packs *found* some 30C NeuEnergy 5S-1P 3300 at only 452g / 141mm x 48mm x 37mm
And it looks like those packs will be really nice for longer runs: 25-30C 5S 4500 538g / 156mm x 43mm x 39mm. Haven't found anything lighter in that capacity.


Concerning the motor I thought you would want about 2200 kv for a 1/8th buggy. So I should go for the higher KV 1512 1.5Y (1900kv), since the 3D is only 1700kv. I am still very confused on that whole kv deal lol I know it means the number of rpm at one volt, but err doesn't clear it up much more lol

EDIT 2: Well if I got it right with a 1700kv motor I get 31k rpm on 5S (18.5V). That's right what you want for a buggy right? Considering the fact that I don't plan on gearing for much top speed, 35 mph should be plenty!

EDIT: Since I am now on a 1512 size motor looks like the Tekin 1700kv RX8 package might be a very good choice for my build... I need to look some more into this setup :) Those should be hitting online stores pretty soon :p Hope Mike gets us a good deal on those :)

EDIT 3: (man I am starting to like those lol) Ok so I looked more into the Tekin combos and they look killer. Price is nice and since I need to wait for 808s to be in stock I might aswell do the same for my powerplant. So I tried using the speed calculator to find out which kv would work best and what size pinion I would need to have. First I want to make sure I got my settings right lol. 808 is the typical 43/13 diff ratio? And well jhautz already told me the spur had 42T so I think I'm good on the settings. Playing around gave me this:

On 1400kv: 25900 RPM. That seems pretty low, is that a problem? Cause with 14T it goes at 35mph and that gives me a good margin to play with.
On 1700kv: 31450 RPM. But now I need a 11T pinion to have a 35mph top speed. Not much margin left on that one.

So what would be the downsides of running the 1400kv motor?


Jhautz, How did you mount your MMM over the rear driveshaft? On some conversions I saw some sort of sevo mount was used... Did you make the mount yourself? I dont have much here to fab such stuff, I need to start hunting for something for another application that would work fine for what I want to do...

I think I'll start shopping for parts online tonight :)

The 808 uses a 43/10 ratio on the pinion/ring gear, so you may need to re-run your speed calculations. The 42T spur gear is stock, and you also have a 41T and 43T as optional gears that will drop right in.

It is also possible to use the center diff mounts from the XT8 truggy to accommodate larger spur gears, but there are a couple things to consider. First, raising the center diff will case the center drive shafts to get very close to the chassis braces. The braces are composite so it is easy to remove a bit of material, but just keep that in mind.

Second, raising the center will also increase the angle of operation of the center shafts so you will probably see a drop in efficiency there and a bit faster wear of the cv joint pins. Again, not a big issue, just something to watch. You will want to watch and maintain those center cv joints anyways; a bit of mantainance there wil allow the pinion, driveshaft and coupling to last a long time.

I also agree with JHautz assessment of the weight balance of the 808. I preferred the handling of the 808 when I placed the battery towards the rear of the chassis. Some weight measurements put the F to R bias nearly identical to the nitro counterpart with the battery to the rear and the ESC over the rear drive shaft. The nitro 808 handles fantastic in most smooth or rough track conditions, so it was my goal to duplicate those characteristics. With my 4S 5000 packs and 1512 motor, my vehicle weight was within an ounce or so of the nitro chassis, so little change from out teams' setups was necessary.

I have used two different methods to mount an esc over the rear shaft. I made a new center diff top plate from carbon fiber that extends back over the rear shaft, similar to what you see on some of the conversion pictures. I also made a 'pedestal' the straddled the driveshaft. i like the pedestal because it sat a bit lower and also did not require removal of the esc do service the center diff. I used a couple top deck posts from the XRAY T2 sedan as posts for the pedestal, but you could also look at the fuel tank mounting posts that will come in your 808 kit.

Bryan
RC America

[Nek]

Thanks a lot for all that good info backfire!!

Man I knew something had to be wrong on my speed calculations, couldn't be good on the first try heh

Good to know I have some options to manage to fit a slipperential with a bigger spur. I think I might order one of those sooner than I think, they look soooo *butter*

And now thanks to the both of you I am sure on where I have to place my ESC :) I'll start looking around for a small cf servo/gyro plate and some small posts. What holes did you use for your posts? The engine holes and/or the ones for the receiver box?

EDIT: With the right gearing now I get 35k RPM on a 1900kv motor on 5S and a 36.5mph top speed with a 14T pinion. Sounds good :)

[SpEEdyBL]

If I were you, I would go with the 1.5Y. Y winds are a tiny bit more efficient than D winds and you can play with the timing on Y winds, while its always best to keep it at zero degrees with D wind motors. So the extra rpm of the 1.5Y shouldn't be a problem.

An even better setup would be a 2Y with a 6s pack that fits underneath the body.

[Nek]

Thanks for that info speedyBL!

But if I were to run the new Tekin combos with the 1900kv motor, does that mean it's a Y wind, or is this winding label a Neu only thing?

I just keep reading great things about Tekin and the RX8 looks like it will be up to par with their other products...

[Nek]

Most of the stuff is ordered just waiting on the Tekin to be out or for the 1512 1.5Y to be in stock :)

I don't know what to get lol I really like the idea of a sensored motor...

I also ordered a sliperential, was just too tempting. So just getting the higher XT8 mount in the front and I guess putting some shims under the RCM mount should do the trick? If I take care of my center CVs I should be fine right?

This thread will most likely turn into a build thread once I get my kit :D

[jhautz]

Well, I just got done installing the slipperential in my 808 sunday and it was a very tight fit. It took quite a bit of dremel work and shimming to get it all to fit without rubbing. It wasnt excatly an easy install. I dont have time right now, but I took pictures and everything along the way. I will be posting pictures of what I needed to do in the "where does it fit" thread in the slipperential forum in a day or 2 once I get a chance.

Quick thumbnail of what needed to be done: Raise center diff 2-3mm, Dremel the spur slot in the chassis wider by 1mm or so, Dremel the plastic rear steering servo mount for clearance for the front outdrive on the slipperentail. The biggest challenge is the length of the outdrives on the slipperential is alot longer than the xray center diff outdrives which makes it basically hit the back of the steering servo mounts. I Had to remove quite a bit of material to get it to fit and not rub.

I havent run it yet in the 808, but it looks like it should work with no issues once you get it shoe horned in there.

[Nek]

Good I've got my dremel handy and love using it haha.

There is this good place to order composite stuff from, cstsales.com Well I think I might order some 2mm cf accent panels for various purposes for my conversion. The ESC mounting tray could use some and I was thinking I could put a small plate under my RCM mount in the rear, and use the XT8 raised mount for the front, or even another cf plate under the stock front mount to be sure to have it all level. From what your saying 2mm should be enough right?

Would you mind also posting a few pics of your custom CF battery tray. I got one of mike's on order but have a few ideas on how I could make a very light battery tray out of CF. thx :)

Oh and u guys use 4 digital scales to properly weight balance your buggy, or you got some nifty tricks to do it in an easier way lol. I think I could get my hands on 4 scales for a few hours to do balancing tests...