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Old 02-16-2019, 08:59 AM   #1
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Default HPI Mini Trophy Resurrection

With the semi build slowing down and all my crawlers ready to go, I need something to wrench on... man I hate winter!

Wandering around the shop, I came across my old Mini Trophy. I had pulled the BL system a while ago and it was sitting in parts, rode hard and put away dirty. Seems like a great project for a rebuild!

This has always been one of my favorite go-fast runners. Love the scale detail and unique design, plus it drives awesome - like a big rally car. Can't just go WFO like my short course trucks, you have to really drive it to keep it on all four tires. Love the way it hunkers down in the back on acceleration too. This truck has seen many ball fields, Dukes of Hazzard style jumps, and more rollovers than I can count. Hasn't broken a thing though, and it's held up pretty well. It does have a lot of slop though, both in the suspension and the driveline. Things are starting to wear out... so let's get to it!

As it came off the shelf... mostly intact.


Tearing it all down...several layers of filth. Had to vaccuum off the workbench when I was done.


After tearing it completely down and giving all the plastic parts a very thorough scrubbing, it's ready to go. I stocked up on spares years ago and never needed them - but I'll use them on the rebuild.


Found a new Ford body on the shelf, as well as a new set of tires. Also dug out a set of old Integy wheels that match the spares - should be a nice combo when all put together.


The chassis wasn't in too bad of shape surprisingly. I do have a new one though in the spares box - may as well put it to good use. I'll keep the old one around just in case (and I can't ever throw anything away anyway)



I've never opened the diffs ever. They were chock full of sticky, thick black grease that has clotted up over the years.They spun, but were getting a bit gritty. Was a royal pain to get it all cleaned out. It has very nice upgraded gears though, not the usual cast crap. Uses the same ratio as Axial, so OD/UD gears are always an option.


I rebuilt the rear diff stock with fresh grease and it's smooth as butter. I used the spring trick and Tamiya AW grease for more of a limited slip style up front. Also I converted over the outputs to 5mm instead of 6. The stock driveshafts were all but worn out and it's much easier to find 5mm parts than 6mm. I did have to use cast Axial pinions though, not sure how well they'll hold up with the machined ring gears. We'll see.


Diffs complete with their new outputs. Got an idea for the rear shaft, not sure it if will pan out, but it should help handling quite a bit.


...and that's it for now! Off to the kids pine car derby. Spent all last weekend getting the cars ready...even trued the wheels. We finished a craptastic 15th out of 32 last ear, hoping to do better this year.

Last edited by OSRC; 02-16-2019 at 01:41 PM.
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Old 02-19-2019, 06:22 AM   #2
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Default Re: HPI Mini Trophy Resurrection

Speaking of the kids pine cars, we came, we saw, we kicked ass. Ran one last year and came in 15th. Went to town this year and ran 2 classes and picked up three trophies. Red car on the left won the Daisy class, and came in 3rd overall. Wasn't fast off the line, but straight up hauled down the flat winning from behind several times. The Green "Bottle Rocket" on the right came in 3rd in the Junior class, which had some tough competition.


So with that over, I can get back to business. The center trans needed a bit of thought to make it work with 5mm outputs. Rear output is fine, though the front included the slipper and is set up for 8mm. After some head scratching, I ended up removing the slipper assembly and used some bushings and washers to set the slipper. Now I can only adjust it using washers sandwiched between the driveshaft and the clutch. It'll be a pain to adjust, but it works.



Center trans rebuilt and running smooth. Cheapie 3800 4 pole motor should have plenty of get up and go.


Steering bits are in. The built in servo saver is terribly weak. I put a zip tie around it - still has some give, but steering response is much much better.


Front diff back in with a Wild Boar shaft now doing driveshaft duties. Stock shaft was in decent shape, just a bit worn around the universal pins.


Nice bit of trickery in the rear - used an old Kyosho viscous coupling... this is an inline slipper and it works wonders on handling. The only quirk of this truck was it would yaw left or right under hard straight line acceleration..has to do with the rear suspension I'd guess. Not sure if this will help, but it should. The front drive will pull 100% and the rear will just kind of follow. Adding the VC in the rear pretty much removes any tendency to fishtail, so we'll see how it works. It's adjustable with diff fluid, so I added 100k to start. I cut down an old Wheely King front axle to make it fit the diff cups.

Last edited by OSRC; 02-19-2019 at 06:25 AM.
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Old 02-19-2019, 07:32 AM   #3
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Default Re: HPI Mini Trophy Resurrection

Here's mine, slightly different from your project but still alive





Side panels are missing in photos, sorry

Last edited by crazykite; 02-19-2019 at 07:41 AM.
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Old 02-19-2019, 07:41 AM   #4
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Default Re: HPI Mini Trophy Resurrection

Cool re-build. I wanna know more about that viscus coupling! Which vehicle is it from? I've never seen one before.
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Old 02-19-2019, 10:44 AM   #5
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Default Re: HPI Mini Trophy Resurrection

And some pics of the rear suspension from different angles. The new Jimco class 1 looks very similar, as do most side by sides.
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Old 02-20-2019, 02:04 PM   #6
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Default Re: HPI Mini Trophy Resurrection

Nice rebuild!

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Old 02-20-2019, 06:38 PM   #7
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Default Re: HPI Mini Trophy Resurrection

Front suspension back on...with a little scrubbing and some WD40 treatment, looks almost new again. Replaced the fixed links front and rear with adjustable links to I can adjust toe angle.


Same with the rear... did a bunch of shimming with some Tamiya 3mm shims to get all the slop out of the suspension - everything is nice and tight now - probably better than when it was new! Thinking a few degrees of rear tow should help with that weird yaw when accelerating too.


Bumpers reinstalled. Had to sand the front bumper quite a bit, it's pretty gouged up. Might put an aluminum skid over it eventually, it's pretty beat.


The chassis has these small humps in the center spine - I have no idea why. So I drilled a nice big hole in it - now I can run a zip tie through it and secure the wiring down low away from the driveline. Note the tight angle on the rear dogbone cup... might be an issue. Seems ok when I test ran it, but I'll be keeping an eye on it. Do have a plan B if it becomes a problem.


Electronics crammed in there. This is a tight chassis...working on this makes wrenching on the Exo seem easy.


About a billion screws later, got the cage reassembled and reinstalled. Do love the look of this even without the body panels.

Last edited by OSRC; 02-20-2019 at 06:40 PM.
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Old 02-20-2019, 06:48 PM   #8
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Default Re: HPI Mini Trophy Resurrection

Quote:
Originally Posted by crazykite View Post
Here's mine, slightly different from your project but still alive
Very nice! I think they look great with just side panels on. HPI made a version like that, though they didn't sell well and are very rare.

Quote:
Originally Posted by JatoTheRipper View Post
Cool re-build. I wanna know more about that viscus coupling! Which vehicle is it from? I've never seen one before.
It's an option from the old Kyosho FW03/FW04 (Super 10) nitro cars. Came with shafts to mount in front or back of the center trans. In a nutshell, up front, you had a RWD bias, and in back a FWD bias. The amount of bias is adjusted via the fluid viscosity. it's really a cool tuning tool, surprised you don't see it in use more often. I think 1/8 buggies and 1/10 on-road could really make good use of it. I ran it out back on my FW04 and the car went from slight power oversteer coming out of turns to accelerating on rails. Really makes a difference.

Quote:
Originally Posted by MAC FAB View Post
And some pics of the rear suspension from different angles. The new Jimco class 1 looks very similar, as do most side by sides.
Quote:
Originally Posted by 860Crawler View Post
Nice rebuild!
Thank you fellas, more pics are forthcoming.
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Old 02-20-2019, 09:07 PM   #9
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Default Re: HPI Mini Trophy Resurrection

Ordinarily I would say that thing is SCREAMING for a solid rear axle.

But...

That suspension and drivetrain setup is so unique and cool!!!
I dont think I remember seeing that. Gonna have to do some research now. Too cool!
It really looks great and I love how you rebuild these really obscure and nearly forgotten rigs into slightly modernized... Well , restomods!
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Old 02-21-2019, 06:11 AM   #10
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Default Re: HPI Mini Trophy Resurrection

Quote:
Originally Posted by OSRC View Post
It's an option from the old Kyosho FW03/FW04 (Super 10) nitro cars. Came with shafts to mount in front or back of the center trans. In a nutshell, up front, you had a RWD bias, and in back a FWD bias. The amount of bias is adjusted via the fluid viscosity. it's really a cool tuning tool, surprised you don't see it in use more often. I think 1/8 buggies and 1/10 on-road could really make good use of it. I ran it out back on my FW04 and the car went from slight power oversteer coming out of turns to accelerating on rails. Really makes a difference.
I tracked it down online, but I can't find any photos if the insides. Can it handle big power that we get from modern day brushless?
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Old 02-21-2019, 07:12 AM   #11
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Default Re: HPI Mini Trophy Resurrection

I had no idea that these trucks even existed! When did HPI make them? I love that rear suspension. It reminds me of the old Losi
JRX 2 buggies & Trucks. I think half of why I like vintage RCs so much is because back then they had such varied & unique suspensions. Now they've all migrated to the exact same suspension designs.

Last edited by Jim85IROC; 02-21-2019 at 08:41 PM.
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Old 02-22-2019, 06:23 AM   #12
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Default Re: HPI Mini Trophy Resurrection

Quote:
Originally Posted by JatoTheRipper View Post
Can it handle big power that we get from modern day brushless?
Don't see why not. My FW04 went 60mph and spun the tires half way there - 1/9 scale car with an O.S. .18 in it that made gobs of power (still have the motor around here somewhere) If it can handle that, BL should be fine. They are very hard to find anymore, and very very expensive when they pop up.

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I had no idea that these trucks even existed! When did HPI make them?
Came and went years ago... maybe 2010 ish? They pop up for sale every now and again. Was created in partnership with a full size race team....the rear suspension was inspired by the 1:1, but the 1:1's body was inspired by the HPI! Pretty cool.

https://www.hpiracing.com/en/kit/103035
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Old 02-23-2019, 07:04 AM   #13
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Default Re: HPI Mini Trophy Resurrection

Front shocks were drained and refilled with 30 weight. What came out of them was brown chunky goo. Nasty. Don't think it was silicone based, I've never seen silicone oil chunk up like that. Greased the O rings, cleaned everything up and they are butter smooth again.


Ditched the stock rear shocks a while ago for some T-maxx 110mm piggybacks. They work great, and didn't need a thing. Oil was even still clear and full. Just cleaned up and reinstalled. I did swap on some dual rate springs I had laying around. They actually work very well..the tight coils compress quickly and the springs gets noticeably harder after that.


Interior and spares cleaned and reinstalled and the chassis is ready to go!


Moved over to the garage from now on...


Ordered this Ford body years ago...opened it up, and it's not a Ford body, it's the stock one. Whoops.... this is what I get for not checking. No matter, I'll just pretend - it's getting painted the same anyway.
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Old 02-23-2019, 11:18 AM   #14
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Default Re: HPI Mini Trophy Resurrection

VERY much like, its making me want to do a TT basher now. I have a huge yard and it would be a ton of fun to have one.
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Old 03-04-2019, 06:56 AM   #15
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Default Re: HPI Mini Trophy Resurrection

Well, cross this one off the list....sorta

Polished up the wheels and the hubs.... the hubs were an odd gunmetal color that clashed with the wheels imo.


Body cut and mounted....tried out some different wheels, but I liked the holy wheels better.


And through the magic of the internet, masked and painted!


Then decals on and done! Went with the old Ford Rough Rider theme...pretty simple and clean, and not a lot of sponsor decals. Absolutely love the stance on these trucks.




Test drove it in the basement and the steering servo is off slightly, and I can't trim it out. Same radio, same serve, same linkages....not sure what happened. Have to tear it back down and recenter the servo horn... *sigh* Rookie mistake.

Last edited by OSRC; 03-04-2019 at 06:59 AM.
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Old 04-08-2019, 06:42 PM   #16
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Default Re: HPI Mini Trophy Resurrection

I also have a Mini Trophy sitting on the shelf, I went thru it and replaced and restore parts after buying it and used 2 or 3 times and been sitting ever since
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Old 05-06-2019, 08:15 PM   #17
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Default Re: HPI Mini Trophy Resurrection

Quote:
Originally Posted by JatoTheRipper View Post
I tracked it down online, but I can't find any photos if the insides. Can it handle big power that we get from modern day brushless?
They handle 3s on a velineon 3800 system just fine. Mine did in Afghanistan at 100 degrees covered in moon dust and I literally beat the crap out of it, never skipped a beat. Suspension components are becoming hard to get now. I picked up mine in 2012 for $35 as a roller at a hobby shop parking lot swap meet sale. Best buy ever. I keep it brushed now to extend its life
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Old 02-22-2020, 08:57 PM   #18
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Default Re: HPI Mini Trophy Resurrection

I must say I'm proud to own this now, thanx again bud.

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