My HPI Mini-Trophy Truck!

[Die-Laughing]

Our club is going to be starting a Scale Trophy Truck Racing Series using the HPI Mini-Trophy Trucks. So far there is about 5 of us that have the trucks and hoping to see more with them in the near future.

I'm going to do a little build thread on my truck and the others might as well.

Modifications:
Castle Sidewinder SCT / 3800kv
Ford F-150 Body & Stock body
Plastic wheels
Prowler XS tires + 2 spares

Club (rough) Rules...
Motor: open
Battery: open
Tires: 4.0" max dia. / Must fit inside body.
Rims: any 1.9"

We figured we would keep it pretty open because the course will be fairly tight & technical so, we want to go fast but, still have the trucks be driveable. A few of us will be running the same ESC/Motor combo that I'm running and one so far has the Flux version that has the 4800kv motor. We will most likely all be running 2s or 3s batteries. I hope to see the others experimenting with different wheel/tire combos to see what works and what doesn't. But, we put a cap on it at 4.0" and it must fit inside the body because, we don't want to be getting ridiculous now, do we?

Couple things to take note of...
1) The driveshaft set screws are pins as well.

2) I used 1 motor bolt that came with the Castle motor and one button head shorty I had laying around. The bolts that came out of the Brushed motor seemed to be too long to fit into the Brushless motor. Make sure your motor wires are clocked to avoid interfering with other things.

3)There is no way to get paper between the spur & pinion but, there is a "sight hole" you can look into to set it by eye/feel. The motor is mounted to a cam system for adjustment. Make sure that the bearings on the main shaft that your spur gear mounts to are fully seated when adjusting your pinion. Basically, just leave the top plastic spur cover bolted down. It may be easier just to remove the whole center differential when swapping motors.

Opening the box!


Ahhhhh! New toys are fun!




Now.. it wouldn't be a very fun race with a stock brushed hpi motor so I picked this up (CC Sidewinder SCT 3800kv)


I wanted to run a different wheel/tire combo and I read that the HPI 26mm wheels work so, I picked up a set that I thought looked good. Along with some Tamiya tires. The wheels in the rear are 6mm offset and the fronts are 0 offset. To my suprise, the wheels and tires fit together loose/sloppy. The wheels are supposed to be 1.9" diameter and the tires are 1.9 but, for some reason the rims sort of "slop" around inside the tire when I mocked them up. There are no foams in the tires but, I wouldn't think that would have anything to do with it. The Tamiya tires are harder than I thought which will work good for this truck.. I just need to get them mounted to some wheels.





I'm on my way to having some fun! Stay tuned for updates!

 

[sally1800]

Those tire look cool. I didn't know the Castle combo came with the fan. :shock: Nice can't wait to get my stuff.

 

[Grizzly4x4]

Very cool!! I love my mini and I think you will too, especially with the 3800. "thumbsup"

The tires are loose because you ordered the HPI Vintage series wheel. The Vintage series wheel has a smaller outer bead because of the special tire they are designed for that has a taller outside sidewall. It gives the look of a musclecar tire. Kind of like a 2.2/3.0 short course wheel.

That are the HPI #3808/#3813 or 3809/3814 wheels right?

 

[Die-Laughing]

Got some more work done...

Removed the cage. sort of a pain but, once its off, everything else is easy to work on.



out with the old..


in with the new..


I removed a plastic "nub" from the chassis to better fit the ESC. Now, the ESC sits on top of that chassis brace with a 5/16" spacer underneath with some double sided tape.
This is the nub:


Nub removed:


two pictures of how the ESC fits:



I clearanced the fan to fit with the rear driveshaft.

fan installed:


wired up:

 

[sally1800]

Thanks for the info Grizzly.. the wheels I got are #2953,#2954 apparently for the HPI Racing Cup Racer 1M Vehicles.
Outer Diameter: 47mm (1.9")
Width: 24.5mm (0.96")
Hex Size: 12mm

I just went by sizes and figured they would work??

:ror:

Hope you didn't glue them.

 

[Grizzly4x4]

I don't see an HPI 2953 wheel on Tower, the HPI web site, or Google. :???:
But I am sure those are the Vintage series wheels.

 

[Grizzly4x4]

From the HPI Site about the Cup Racer.

*Note*
If you want to use the old wheels from your existing Mini, you can! Just be sure to use the old tires also since the new Cup Racer tires will only fit on the new wheels.

::HPI RACING:: - Cup Racer

If you stick to the standard touring car wheels and avoid the "Vintage" or "Cup Racer" wheels they will work fine. I've actually glued crawler tires to the Vintage wheels and had no problems, but with the stiff Tamiya tires I don't know how they will work.

 

[neillarson]

I have to see if I can find some stiffer springs for the rear and add a second set of shocks. When I out a 5000MHr Hard Case in it, it Really sags.

 

[Die-Laughing]

Update in post #4!! also.. some good info added to post #1

Now, I just have to do some finishing up of the wiring and figure out how to hook up the fan (never had a fan before).

I want to put some 70w oil on the rear shocks and see if any of my LOSI springs fit on the HPI shocks out back.

My 2s battery fits nice & snug in there. Haven't tried 3s yet.

So far its been fun working on this thing!

 

[KBrog]

I was onroad racing mine. Made some f/r anti-sway bars that helped a lot. Been looking for about a year for "GOOD" tires to fit this truck. I have bad news. The Tamiya Rock Cruiser M/T Tires are worse than stock. The only tires I did find that will fit are some of the RC4WD 1.9's. Havent tried any though. Looked at a ton of buggy tires. All are to big or give no info on size and my budget wont allow blind trial.

Need a tire that is 3.75-4" and 1-1.4" wide.

 

[Die-Laughing]

Thanks KBrog.. I'm gonna see what I can do with the Tamiya tires and I'm also going to try the RC4WD Dirt Grabber tires.. I found a used set for cheap.

Well, I put 70w shock oil in the rear shocks and they feel better (haven't run it yet though) and my losi springs aren't nearly firm enough to replace the HPI springs. Those suckers are stiff as hell.
I wanted to put 50w oil in the front shocks and I was trying to take the cap off (really tight) so, I used a pliers to hold onto the body and poked a hole right in the side of the shock body with the pliers. :evil:
Now, I need to figure out if im going to replace or upgrade the front shocks. I heard the Blitz shocks work in the front too but, Im not sure.

Edit: ordered some stock Blitz front shocks for $7 shipped. we'll see what happens.

 

[sally1800]

Thanks KBrog.. I'm gonna see what I can do with the Tamiya tires and I'm also going to try the RC4WD Dirt Grabber tires.. I found a used set for cheap.

Well, I put 70w shock oil in the rear shocks and they feel better (haven't run it yet though) and my losi springs aren't nearly firm enough to replace the HPI springs. Those suckers are stiff as hell.
I wanted to put 50w oil in the front shocks and I was trying to take the cap off (really tight) so, I used a pliers to hold onto the body and poked a hole right in the side of the shock body with the pliers. :evil:
Now, I need to figure out if im going to replace or upgrade the front shocks. I heard the Blitz shocks work in the front too but, Im not sure.

Bet you can run traxxas 3.5 big bore. Like in the front of a slash 4x4

 

[TURTLE]

Switch out that junk servo while you got it apart!

 

[Die-Laughing]

Switch out that junk servo while you got it apart!

Yeah? I have an extra Hitec HS645MG.. I'll throw that in there.

 

[TURTLE]

Yeah? I have an extra Hitec HS645MG.. I'll throw that in there.

I would put something with a speed of .09 seconds and 120+ oz of torque.

A 645 is SLOW!

 

[Die-Laughing]

Your right.. the 645 is much slower than I thought. I can't find a decent servo for anything less than $65.. that's quite pricey. This is supposed to be a budget build! :twisted:

Does anyone know what's involved in eliminating the servo saver on these trucks?

 

[KBrog]

Does anyone know what's involved in eliminating the servo saver on these trucks?

I CA glued the servo saver together. It made the steering much more responsive. Golden Horizon makes a nice servo arm for the MTDT. I thought I had seen a aluminum upgrade servo saver assembley in my web searching somewhere but now I cant seem to find it.

 

[neillarson]

Savox SC-1258TG is probably the best buy out there, I ran them in all my RC10 vehicles and have one to go in my Mini TT if I find the time.

Speed: .08 sec/60 deg. @ 6v
Torque: 9.0/167 kg-cm/oz-in @6v

But you are right, it is $68.

 

[TURTLE]

I CA glued the servo saver together. It made the steering much more responsive. Golden Horizon makes a nice servo arm for the MTDT. I thought I had seen a aluminum upgrade servo saver assembley in my web searching somewhere but now I cant seem to find it.

GH racing."thumbsup"

http://www.ghhobby.com/products.php?cat=44

Savox SC-1258TG is probably the best buy out there, I ran them in all my RC10 vehicles and have one to go in my Mini TT if I find the time.

Speed: .08 sec/60 deg. @ 6v
Torque: 9.0/167 kg-cm/oz-in @6v

But you are right, it is $68.

I put the low profile Savox 1251 in my TT and Rally car and it is working quite well, though the price is about the same. The stock doesn't have to be replaced though it does develop quite a bit of slop over time, I figure if you have it apart you might as well replace it.

 

[OSRC]

Here are the shocks I used on mine - Maxx Shocks from Ebay - they feel pretty good. Really needs a stiff spring due to leverage from the trailing arm, and these are about the same, if not a bit stiffer than stock.

I run a 3125 BL in mine and it's a beast. That SC motor is going to be insane! Enjoy, it's a fun truck!