Mayzie12's 8s Hong Nor 8th Scale Short Course

[mayzie12]

8s in an eighth scale short course truck. What can possibly go wrong!

 

Well, a lot apparantly.

 

This came about mainly, due to having an 8s 250a MGM lying around. I bought Bez's old Hong Nor short course truck a couple of years back, which is just Hong Nor CR Buggy bits, plonked onto a CRT chassis. It sadly didnt last long as a short course truck, and is now a touring car which i run as my 808 car at Rossa. But i always wanted another, and after dabbling with a hyper SC i made on the same theory, i've went back to Hong Nor. Its easier only have one big set of spares!

 

Ive done quite a bit of work to the car upto this point. Including 3d printed Receiver box, Lipo Tray, ESC mounts and body work all of which now is starting to come undone after a couple of weeks hard bashing (including well over 100 cartwheels).

 

Main Specs of the car;

• MGM 250a ESC (in another car now)
• Sirius 1717 Motor (RIP, Sensor fell off, attempted fix failed, still on look out for replacement)
• HPI ATTK-8 Body Shell (still going, Just)
• Alturn Digital HT Servo (RIP, completely Died)
• Lots and Lots and Lots of Lipos (some damaged)

 

MAIN SPECS UPDATED 7/06/16

• Turnigy Trackstar 8s 200a ESC
• SKYRC 1350KV 6 Pole Motor
• HPI ATTK-8 Body (Still wanting another SC8 shell
• Savox 1256
• Even more lipos......

 

MAIN SPECS UPDATED 18/12/16

• Turnigy Trackstar 8s 200a ESC
• SKYRC 730KV (5th Scale Motor)
• Team Associated SC8 Shell
• Savox 1256
• Not Many Lipos, Need More, many...

 

Finally have the car reliable (almost). Had 3 sets of packs today through it before anything went wrong, and things only broke when it hit a bump and cartwheeled several times. Initally had the car cogging a lot off the line, this was solved by tweaking a few settings in the ESC, mainly the PWM frequency. Car now runs sweet as a nut with the ESC temps no higher than 50C, and the motor temp hovering around 60C.

I've had a couple of issues with the ESC overheating in the past, which has led me to create a 3rd heatsink that sits on top (Gold One), and so far its done its job

 

Have a few things to sort out now, Mainly the Lipo tray and the ESC mount which broke on the last bash. ESC mount snapped from one of the accidents. Ive now made this a bit shorter, should hopefully reduce the chance of it snapping again. The Lipo tray i have made the walls thicker, and made it a little bit smaller as it was a tad large for what i needed and the lipos could move about a bit.

 

Also need to sort the bodyshell. Not too impressed with it to be honest. I sold the Team Associated SC8 shell with the Hyper SC i built, and now wishing i had not. It was way stronger and too a lot more abuse. Going to take quite a bit of shoo goo to get this back together.

Also might need to add some new rubber. Ive ran GRP buggy wheels for last year or too. There pretty cheap pre-mounted and there the only wheels and tyres which seem to survive 8s, as ive never had one blow up on me yet. Only problem is there more for racing so the grip on the grass is pretty poor!, Especially when they wear to this is only a couple of weeks!

 

 

Hopefully get a video of it next time im out

 

Edited December 18, 2016 by mayzie12

[mayzie12]

Well i took it back out with the new stuff printed, Lipo Tray, ESC Mounts and the body repaired and eh yeah. This....

 

 

Hit a disguised brick in the grass at a rather high speed. The car stopped but everything else kinda kept going

 

Lipos flew out as did the body and ESC was hanging by a thread. The car itself is still fine, was only my printed bits that broke. Sadly one of my new lipos got a ding, seems to be okay, didn't get hot on the drive back to the car and still balances perfectly, so will just keep an eye on it. Also managed to snap a T-Bone Bumper which i always find a good achievement!

 

 

So now another super dense lipo tray is printed with double the % infill and 5.5mm thick walls on the front and back rather than 4mm, if this breaks i have another wee tweak which i really should of done but the idea escaped me at the time of printing sadly

I've tweaked the design of the mounts a bit, making the top surface a little thicker and the ESC mount is now way thicker than before. Will post up pics when done, and hopefully get a video next time out if it lasts longer

[mayzie12]

New stuff is all done. Thicker Lipo tray, denser body mounts and another ESC mount which allowed me to cable tie the ESC on as the 4 M2 screws available to mount the ESC were not really up to the job! The damaged Lipo from last time ran without problems too. No extra heat, no swelling, all cells still good so looks like its just a bit out of shape but the internals have all survived

Pics:

 

Everything held up which makes a change
I was worried the cable ties holding the ESC in place would affect the cooling as they covered the fans, and sadly they did. ESC overheated and caused cutting out. Checked the data log and previously the ESC was running around 50c steady. With this it was running all the way to 100c

 

 

Going to need to start a fresh on the idea for this ESC mount, Current idea and several iterations have not worked. Now thinking of a "cradle" type thing which clamps the ESC in, yet leaves all of the fans uncovered and should only require 4 bolts to get the ESC out. Also going to try and fit another fan to the third heatsink i have previously added.

Also the motor today was "Sizzling" It was quite hot ambient temp, around 20c but the motor should not get to the stage it was. I cant really gear it up until i get the esc temps under control, and the logs say its already pulling 200a average and more when im going for it. Only thing is to get a lower KV motor as to be honest the car is really quite quick, and im never on full throttle, generally only 50-75%. According to the logs the car is hitting peaks of 120-140km/h (around 70ish) which is pretty mad

 

Also finally got some video, it aint the best as it was a mount i printed up so i could use my phone through go-pro mounts stuck to the bottome of my tx but here it is:

 

Edited May 10, 2016 by mayzie12

[mayzie12]

New ESC mount designed and made. Seems to work well so far. Put a set of slicks on the car just to give it a test run in my street and it remained nice and cool!

 

 

Its just a 5v fan from an old HW EZRun Pro. One thing i can say is its clearly a pretty pants fan as i can feel way more air coming out of the tiny fans built into the ESC than this one i added to the top. I think the ESC fans run off 10-12v as thats the main bus voltage so might try and pick up a 40mm fan of the voltage and wire it into the ESC as at the moment im just running it from a spare socket in the RX.

Data logs from the test. As can be seen by the green line, the car gets a shift on!

 

Next thing to sort is the handling and first on that list in the steering. The servo seems to lose its centre. Initially the car goes nice and straight then after 5 mins of bashing it seems to pull heavily to one side. Is this a sign the servo is on its way out? I bought two at the same time and one has already failed (alturn digital servos). Have a 1256 Savox ive had in the 808 car for ROSSA for ages not being used so going to slot that in and see if it fixes it.

[mayzie12]

Well things have taken a turn for the worse. Car was going good, ESC temps down, Savox servo had sorted the steering then this....

 

 

Pinion shattered and looks like it has taken my 1717 with it

Motor just cogs like hell now, opened it up to have a quick look but couldnt see anything obvious, so will need to do a full tear down and check. I have already re-done the connectors thinking one of them had gone bad but this hasnt sorted it. Really hoping i can salvage the motor as i was needing it for my speed cars too.

[bertberr]

Jeez that thing has some grunt!!!  Some traction roll issues on that grass though...!!!  Shame about the motor, but have to say I'm impressed by your improvisation and perserverence - always enjoy reading about home builds / modified rigs - will be following this one with interest.

[mayzie12]

Cheers!

 

I think i have come to the bottom of the motor. Looks like one of the sensors has came off the rotor. So I'm hoping it can be glued back in place and sort it. (just need to find the correct glue)

 

What it currently looks like

 

What its meant to look like

[mayzie12]

Well an attempted fix on the rotor didnt work sadly. The lines all line up, the motor runs, but pretty rough and gets hot quick. My guess is the timing is out. The lines are bang on as they were so thinking maybe the shaft has twisted ever so slightly.

 

Also the MGM 250a ESC that was in it, is now in my speed car.

So, i ran it briefly as below, castle 1512 2650kv, with a hobbywing 150a and a 4s.

 

 

Stuck a 20T pinion on and the esc got a tad hot after 2 packs, which tbh was probably going to happy as i was being a bit greedy to try and keep the speed up. Still, i found the whole 4s experience a bit underwhelming.

I have since got another 8s ESC and motor on order and this time i have got for a super budget option (was around £110 for them both). Needing to rearrange the layout a bit, moving the lipo tray, ESC and motor location. So another ESC mount will be printed, along with another lipo tray (another 15 hour print!). Luckily i can just flip the motor mount to the other side and its all still good!

Also printing another rx box as the new ESC does not have a BEC, so another larger RX box is needed to accommodate it.

So far have got the ESC mounted, and the motor mount moved. Printing another rx box at this moment. Just needing to do the lipo tray and wait for the motor to arrive.

Will get pics when its together

[mayzie12]

Got the new combo in and tried today. Toro 1350KV Motor and the Trackstar 8s ESC.

Flipped the motor mount to the other side of the car to make enough space for the larger ESC. Printed a plate to mount the ESC where the engine would be on a Nitro version.

Changing the motor and ESC location also meant printing another Lipo Tray. Made it slightly smaller, so the lipos are a nice snug fit, no rattling around and no foam needed anymore to hold them tight.

Finally another RX box was printed as the ESC didnt have a BEC built in so had to get one, and make enough space to accommodate it.

Gave the car a quick run on my street and its really pretty good. Motor got hot, but not too bad, ESC was slightly warm. So it should run fine. This was on 20/48 gearing. Car still wheelies on demand at any speed, and at a guess is still cracking 60-70mph!

Shell is getting a bit bad but another repair should sort it out.

 

 

Main things i need to do is create a switch for the BEC, as i use an inline resistor to slowly charge up the caps in the ESC so i dont get a massive spark when i connect 8s to the ESC. But since the BEC runs constantly when powered, the second i take the resistor out to then plug the lipo in, i get a massive spark as the BEC has used the charge in the caps. Will make a switch so i can switch the BEC on one ive connected everything up.

 

Also FINALLY managed to get another SC8 shell from team associated. Much stronger shell, have not painted it yet, going to wait until the HPI one is properly knackered first.

 

 

[Carpmart]

Good work mate....  

 

seems you've worked through your issues!  

[mayzie12]

On 18/06/2016 at 19:52, Carpmart said:

Good work mate....  

 

seems you've worked through your issues!  

 

Cheers. Think i have most of them sorted. Although wired in a switch, only to wire it in between the BEC and receiver, not the BEC and the batteries, so i still get a spark.......

Main thing is now to sort out the handling, which will be interesting, as ive really got nothing to go off.

 

Also managed to get a quick vid of how it goes in the new incarnation. It also highlight why i really shouldnt run it in the street, and  why i should of fixed the body first...

Its now hanging on the washing line drying before i fill it with 2 tonnes of shoo goo

 

[Daveyb84]

The wheelies look fun

It's definitely goes well mate

[mayzie12]

On 20/06/2016 at 17:02, Daveyb84 said:

The wheelies look fun

It's definitely goes well mate

Cheers Davey, Just gotta get it handling now!

 

Was looking over the car while planning on adjusting a few things and noticed one of the upper arms is cracked almost right through. Currently trying to source a replacement. Its a PBS kit on the front which seems to be incredibly rare. I've found a whole kit, which says 2 months delivery, which imo makes it sound dodgey. Also cannot find any upper arms on there own at all for it. Might just have to use other upper arms if i can find any the correct length or change it back to a normal front end which would be a shame. Dont want to scrap the whole PBS kit cause of one break!

[mayzie12]

It's been a while.....

 

Changed the front end from the PBS back to the normal setup. Mainly as i could simply not find a replacement part, not mainly cause i whacked it into a pole and ruined the lower arms too

 

Got the switch installed correctly, and i now have a nice no spark connection which is nice.

Also painted the SC8 shell (No pics as its crap). I generally dont care about the painting of the shells, they only get ruined

 

Overall the car is standing up excellent. ESC is performing way above what i ever thought it would, for an £80 unit you cant wrong, although i feel im hardly stressing it on a small motor and car compared to what it is meant to run.

Sadly my cheapo motor has not faired so well. The car came to a smooth stop when i had it out today, with a hint of smoke. Yes it was really that hot. Looks like it has demagnatised as it now spins pretty much freely. Took the endcap off for a quick look and the blackness of the copper agrees....

 

 

Not quite sure what my next move is to be honest. Its only really motors that have let me down. Only next logical step is to go to a 1/5th scale motor and see if i can squeeze it in. I've been looking at doing a mad 5ive for ages now, which i would need the motor for. Im going to 3D print a model of the motor i have in mind, see how i can get it to fit and go from there!

[mayzie12]

So i put back my 2650 Castle in it, just to keep it going until i decided on the motor, kept it on the 20/48 gearing, only ran it 4s. 3 packs later motor gone again......

Same that happened on my 1717, the sensor fell off the rotor. 99% down to heat. So im obviously ruining motors by pushing then too hard

 

So I've given it one more shot, ordered a 2200kv Tenshock, going to stay on 4/5s and see it how it goes. I'm mainly trying to keep the speed up of the car, its what makes it a good fun imo. So we will see how this lasts and go from there.

 

Also from the 4s running with my 2650, lipos are clearly not up to the job as can be seen.....

 

 

Fresh off on the right, one that has been off for around 10 mins in the middle and a new charged on the left

 

This is, they all discharge perfectly balanced, are not hot, not even above 30C, and they all balance perfectly when charged. Havent tried a capacity check yet. But i reckon there just not up to the job.

 

Motor should be here soon as its from RCMart, so will see how it goes when that is slotted in!

Edited August 21, 2016 by mayzie12

[capri-boy]

What diff's is it running Craig?  Not a great comparison but my X1 CRT-e still has X1 CRT diffs but runs a Hyper ST 52t centre.  Running 17/52 with an 1800kv on 5S with Truggy wheels and it never breaks a sweat.

 

 

 

 

[mayzie12]

Just the stock 13/43 arrangement. The castle motor was a fake so maybe that was part of it. Also the SkyRC motor that i used on 8s was a $40 motor, again, very cheap. My 1717 only failed due to the pinion shattering. So im hoping a better motor will cure it.

 

My gearing is a bit taller than yours but my wheels only being buggy ones should bring it back down a bit more.

 

Interesting thing is when the motor failed it took a lipo with it, but not the ESC......

[mayzie12]

New motor arrived!

 

 

Also printed a 3d model of a TP Power 5670 800kv.

Good news is it fits....kind of....

 

It will only fit where the ESC currently is, which is OK, as the ESC will fit the other side. It does mean however i will need another motor mount that's flipped the other way.

 

 

Wont be ordering the TP Motor for a few weeks. so will see how it runs on the new Tenshock in the meantime. Going to be sticking to 5/6s.

[Carpmart]

What are you bringing down for ROSSA Craig?  6s won't cut it mate!  

[mayzie12]

5 hours ago, Carpmart said:

What are you bringing down for ROSSA Craig?  6s won't cut it mate!  

 

I'll have this, and my 808 car which is 8s course

 

I've been searching high and low for a 1717 to go back to 8s but there like hens teeth! I've tried the cheapo option with those SKYRC things and it just broke.... And due to TP motors lead time i wouldnt be here in time either

 

Theres been a guy selling a XL2/1717 combo on ebay for yonks. Might just go over and see if he will split

 

[mayzie12]

Aaaaand were back!

 

Took the car to ROSSA, attempted the tower, which it has done everytime, but sadly without Bez being there with his top guestimates on ramp setup, we couldnt get it to work. I did however do this!

 

 

Cheers to Paul for capturing it!

There was a bit of damage to the car, not really major, it still all moved fine and nothing is bent! Only broken part was a T-Bone and the extender part which i have got a replacement bumper, then bought some nylon to make the extender. It seems silly tough if a little brittle so will see how it takes the impact.

 

 

Also the shell on that jump and all the failed ones where it whacked into the tower, was the SC8 shell. Its still abosultely fine which is a testament to its strength!

 

Just touched the car for the first time since then, always take a break after ROSSA. I've went and got a 5th scale motor for it, not quite the TP Power one, money is tight atm, but this should still do the job. Its a 730kv SKYRC job. Should be fine on 8s. Will see how the ESC likes a bigger motor however. Pic below shows a 1717 (i did get another after all) on top and the new motor on the bottom!

 

 

Luckily i have a few 8mm bore mod 1 pinions, but i do need a couple of bigger ones. Current gearing is 32/48 which is only good for 65ish, which doesnt cut it! Will probably  order some in the new year from Kershaws.

 

Got a day off on Monday, so will try and get it out then if its fair.

After that i need to get some more lipos, only two of the initial 4 4s packs i bought for this have survived. Mainly i think due them just not being good enough.

 

Finally some pictures of the car which were taken down at ROSSA.

[mayzie12]

Well i do like it when a plan comes together!

 

Just blasted it around the street. Feels just as quick (even though its geared for less top end). Can only assume its using the full range of the motor when it wasnt before.

Tonnes of torque, no cogging, motor nice and cool even after 10 minutes of WOT starts and going flat out down the road. Same with the ESC. So looks like the electric bits are finally under control.

Next up if the gears.... The 8mm bore pinions i have are from kershaw, seems like there is quite a lot of wear even after the initial run. It was definitely a tad loose the mesh so i have tightened it up, but even still id say the wear is high. I did ruin one of these pinions down at ROSSA but this happened when a pinion shattered against it (was using it as a spur at this time). I did however borrow a gear that was made by RW from another speed runner and it showed no wear at all. Might need to just plump for the more expensive ones from RW. Will see how it lasts first.

Also managed to crash the car Was only doing 60ish, but it was only my cars parked on the street before anyone asks! Cartwheeled for a good 15m on tarmac...

Adding more weight though it does crash harder... a broken arm only and a crack in the shell. On the lookout again for another SC8 shell but in stock no where....

 

All fixed now, just waiting on some drier ground as i cannot be arsed cleaning it if it gets all muddy!

[just rolling]

Wot kinda wheels and tires you using? Struggle to keep mine on with just 6s, thanks 

[mayzie12]

49 minutes ago, just rolling said:

Wot kinda wheels and tires you using? Struggle to keep mine on with just 6s, thanks 

 

49 minutes ago, just rolling said:

 

 

 

Using pre-mounted GRPs. 

There pretty cheap direct, and they have never come unglued and I've ran several sets right down.

[just rolling]

15 minutes ago, mayzie12 said:

 

 

 

 

Using pre-mounted GRPs. 

There pretty cheap direct, and they have never come unglued and I've ran several sets right down.

Who do you get them from?  Thanks again