Fastest HPI Sport 3

[Redback]

Parts arrived, still cant run 30mm foams on front as turnbuckles are to big, cut off the nub stopping the backs being fitted, have to run 26mm on front then as not enough axle stub for hub extender.
Diffuser added and cut back to allow the foams to expand, recentered servo, need to shorten and update motorwire to 6mm bullets, body cut and paint to do.

 

[Redback]

Not happy, spur gear melted doing a range check, was going 5mph at most. Really cheesed off, been nothing but a problem child, one run broke chub, 2nd run melted gear. 😞

 

Feeling a bit of regret getting this, had high hopes but so far nothing but dissapointment.

 

Painted the body tho turned out ok for spare empty cans.

Edited June 13, 2023 by Redback

[Grogg]

I was under the impression that you where using two pinion gears, instead of the traditional pinion and spur gear setup.

[Redback]

On 11/06/2023 at 03:37, Grogg said:

I was under the impression that you where using two pinion gears, instead of the traditional pinion and spur gear setup.

Not to start with, was going to try the high speed gearing, skipping that, have to grind down a pinion to fit or chop the chassis somewhat, going to try grinding a pinion.

[Grogg]

12 minutes ago, Redback said:

Not to start with, was going to try the high speed gearing, skipping that, have to grind down a pinion to fit or chop the chassis somewhat, going to try grinding a pinion.

 

I would chop the chassis personally, a hell of a lot of RC cars have a chunk of the chassis cut out already for the spur gear, even off roaders  exposing them to the ground below them - the HoBao Hyper Cage Truggy in fact all HoBaos and a lot of Armas and Traxxas RC do some even have the pinion gear exposed as stock.

[Redback]

No i wont chop the chassis, ill chop the pinion to clear the chassis 🙂

Poor mans lathe, run the motor and the dremel to get a balanced cut.

 

[Grogg]

It basically looks like you're doing the same mods as that Stew Mac guy on YouTube and the Tamiya Club forums does to Tamiya TT-02 chassis to get them to go over 100mph, right down to the pinion and spur gear cover modification.  Basically get your pinion and spur tooth count to as close to 1 to 1 as possible if not have a higher tooth pinion gear compared to your spur gear.

 

And I see now having seen your most recent pics why you would ground down a pinion gear rather than modify the chassis to accept a pinion gear as a spur gear.

[Redback]

Yeah cutting the chassis is always a last resort as its not a reversable modification and the chassis on these contain the spur gear housing that means any cutting is a new chassis.
Also i use the same gears for the other cars so a cut down one is good for them too.
The hpi and wheels is a pain in the butt, the rears have a nub when cut off makes fitment better but still have to move the shocks way in etc.
The fronts are worse with the long steering arms and top arm pivot not giving clearance.

Found that contact drag foams fit front and back, backs wont clear the fronts and are quite a bit wider.
Could run 2 sets of front drag foams, these are the only ones that fit as 26 - 30mm x 60mm foams will not fit the fronts.
These also vastly improve the handeling and stop it being super twitchy on steering input. Even with dual rate all the way down with 26mm fronts it was all over the place.

 

Now the body fitment is another thing, either i cut out lots of body or trim the wheel.

Will probably get some fronts for the back and keep the back ones as backups.

 

On 14/06/2023 at 00:52, Grogg said:

It basically looks like you're doing the same mods as that Stew Mac guy on YouTube and the Tamiya Club forums does to Tamiya TT-02 chassis to get them to go over 100mph, right down to the pinion and spur gear cover modification.  Basically get your pinion and spur tooth count to as close to 1 to 1 as possible if not have a higher tooth pinion gear compared to your spur gear.

 

And I see now having seen your most recent pics why you would ground down a pinion gear rather than modify the chassis to accept a pinion gear as a spur gear.

Did you book into rossa? Yes not seen stews gearing video but i also find running negative gearing eg 32t pinion 27t spur good as you can not get small spur gears like you can get pinions.
Also not sure with the tamiya but for the ftx you need to make a custom drive shaft to accept pinions, for the hpi is a bit easier aslong as you have the right bearings to make up for the lost space.

[Grogg]

On 15/06/2023 at 20:20, Redback said:

Yeah cutting the chassis is always a last resort as its not a reversable modification and the chassis on these contain the spur gear housing that means any cutting is a new chassis.
Also i use the same gears for the other cars so a cut down one is good for them too.
The hpi and wheels is a pain in the butt, the rears have a nub when cut off makes fitment better but still have to move the shocks way in etc.
The fronts are worse with the long steering arms and top arm pivot not giving clearance.

Found that contact drag foams fit front and back, backs wont clear the fronts and are quite a bit wider.
Could run 2 sets of front drag foams, these are the only ones that fit as 26 - 30mm x 60mm foams will not fit the fronts.
These also vastly improve the handeling and stop it being super twitchy on steering input. Even with dual rate all the way down with 26mm fronts it was all over the place.

 

Now the body fitment is another thing, either i cut out lots of body or trim the wheel.

Will probably get some fronts for the back and keep the back ones as backups.

 

Did you book into rossa? Yes not seen stews gearing video but i also find running negative gearing eg 32t pinion 27t spur good as you can not get small spur gears like you can get pinions.
Also not sure with the tamiya but for the ftx you need to make a custom drive shaft to accept pinions, for the hpi is a bit easier aslong as you have the right bearings to make up for the lost space.

 

 

No I haven't booked in yet, the goal is to attend one in 2024, I just have so much going on at the moment that not only have I made no progress towards finishing my Rock Socker, I haven't even started my 100mph TT-02 build yet.  I have been looking into what it takes and is involved in attending R.O.S.S.A, the costs, time, is it worth attending  it just for 1 RC car or should I build another or two - it's an 800+ mile round trip for me and it will easily cost me a grand just to attend never mind enter an RC car, as well as continuing with my research for my 100mph TT-02 build.

 

Out of curiosity have you seen these  - I'm not in anyway recommending the one I've linked to I don't even know if it's compatible with the HPI Sport but they are widely available for many many brands and models of RC cars though in some cases you may have to use one designed for one model but is also compatible with yours, thanks to one of those I can use just about every pinion and spur gear combination in my TT-02, and it looks like you can do similar with your HPI.  I'm actually planning on running either a 55 or 60 tooth pinion combined with either a 35, 40, or 45 tooth Kyosho spur gear.

 

Out of curiosity what are your plans for suspension and ''stance'', personally I plan or rather planned on going as stiff as possible, the stiffest springs and thickest suspension oil I can find for both front and rear sets of suspension, but then I saw this Kevin Talbot video where he shows you up close what was done for the rear suspension of the RC car that just broke the world record - which is now making me rethink my idea of using the standard suspension layout and copying what David did to the rear suspension of his world record breaking RC car.  As far as stance goes, I'm planning on balancing the car equally over the front to 2 wheels and the rear 2 wheels - I found a fancy set of scales that measures how much weight each wheel is supporting and weight distribution,  so there will be more weight, not much more over the front wheels compared to the rear wheels.  Meaning the car will be slightly lower at the front compared to the rear.  As far as diifs goes, I'm planning on using oil filled diffs for both the front and rear, with much thinner diff fluid in the rear diff, and the thickest diff fluid you can get before you get to gels and silicone for the front - after all these RC cars are designed and modified to handle like all American cars amazing at going in a straight line but can't turn for love or money so why even bother with steering and why not just lock it so it so that the RC car can only go in a straight line and not turn, though I'm still considering whether or not I'll upgrade the diff gears to either HPI ones or the ones that are used on a Tamiya DT-03

 

 

[Redback]

Rossa results, with round 1 with the hpi, the 2 pole got very hot so swapped out for the hobbywing setup used in the banzai, then it started to cut out at 100% throttle (no failsafe, no steering) so didnt run it again.
Same gearing all runs 1.1 32t - 32t

 

Sat 11 HPI RS3 SPORT ELECTRIC 4 CELL 4S 75.42 75.42  (Castle + 2 pole)
Sat 11 HPI RS3 SPORT ELECTRIC 4 CELL 4S 75.76 75.59  (Castle + 2 pole)
Sat 11 HPI RS3 SPORT ELECTRIC 4 CELL 4S 80.83 80.50  New P.B (Hobbywing xr8 sct combo)
Sat 11 HPI RS3 SPORT ELECTRIC 4 CELL 4S 66.84 66.75 (Hobbywing cuttout)
Sat 11 HPI RS3 SPORT ELECTRIC 2 CELL 2S - 39.47 Only 1 Trap Working (Hobbywing cuttout)

 

Overall ok results, steering deadzone is massive, needs lots of work but good base to improve.