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Old 10-08-2012, 05:58 PM   #121
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Default HPI SPRINT 2 SPORT Trans AM car Roller + Extras AVAILABLE

SOLD


If you're looking for that 1st Sow's Ear to make a Silk Purse or one for your girl friend, your ankle biter or just as a back up - - -

There's a HPI SPRINT 2 SPORT Trans AM car Roller + Extras that's available.

When it comes to a roller, either posted on R/C Tech or eBay, I've seen people asking for alot more $$$ for less.

Dan's asking price is very reasonable (IMO).

The front universal dogbones (cvd's) alone are worth $34 list!


Click this link for details - HPI SPRINT 2 SPORT Trans AM car


Last edited by Marv; 10-10-2012 at 07:00 PM.
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Old 10-09-2012, 05:21 AM   #122
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Hello

About your belt tensioner mod: I would say you did great with the bits you had, or found, but this kind of tensioner is definitely something I would no do because you are pulling the belt away from the drive pulley, reducing the number of teeth that can be driven but this pulley. I don't know if I explain myself very well, but in my humble opinion one should always put a tensioner in a way it pushes the belt against the pulleys rather than away. The pulley of this car are already tiny ( 14t ?) which is not great for belt wrap and forces the user to apply more tension to the belt, thus increasing drag.

So if you use a powerful motor this is not good because there's a good chance you belt wil slip and destroy itself + the pulley, and if you run stock motors this isn't right either because you will have too much drag in your drivetrain.

I would look into a conventional tensioner, maybe with bigger flanged bearings if the belt is still loose on the tightest setting.

Anyway I think this car is really cool and everyone at my club ( myself included ) still remembers having his ass kicked real bad by JM " Lord " Betticher driving a sprint 2, a few years ago. He had taken the car out of its box the evening before the race, threw electronics in it and "the rest is history", haha So you are perfectly right in thinking it's underrated. Nice thread.
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Old 10-09-2012, 05:30 AM   #123
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double post.
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Old 10-10-2012, 07:22 PM   #124
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Default DOG BONE SLOP FIX - A FIX FOR THE FIX

Everyone has their own voodoo. This is my voodoo. This is what works for me.



DOG BONE SLOP FIX - A FIX FOR THE FIX

CLICK THUMBNAILS FOR LARGE PICTURES

This fix replaces the HPI 'O' ring fix for dog bone slop.


Advantages over the HPI 'O' ring fix:
The springs will flex with the suspension & steering, compress and decompress - The 'O' rings don't.
The springs exert less lateral pressure on the inner axle bearing race - Longer bearing life, less drag.
The springs won't need to be replaced like the 'O' rings, unless you lose them.

HPI Sprint 2 Mods - Making a silk purse from a sow's ear.-theycompresscopy.jpg


The spring in the G2 Pilot 07 is .218" in diameter and fits in the S2 diff cups quite nicely.

Other ball point pen springs have a smaller diameter which will cause them to 'walk' in the cups.

HPI Sprint 2 Mods - Making a silk purse from a sow's ear.-g2.jpg



WHAT YOU NEED:
Two G2 Pilot Gel Pens (NOT THE MINI's) - I used the G2 Pilot 07 (07 denotes fine point)
Two G2's cost under $6.00 at WalMart
A pair of side cutters (aka dikes)
A pair of tweezers - Nice to have = To insert springs in diff cups

HPI Sprint 2 Mods - Making a silk purse from a sow's ear.-g2pilot07gelpenspring-master.jpg


FRONT DIFF CUP SPRINGS
You are only going to use the ends of the spring.

Take one spring, cut it in half.
Rotate the spring so the wound end on the tight side is facing up.
Counting that half coil, count 5-1/2 coils towards the end that you cut in the center.
You should come up with 6 coils total counting the two half coils.
Cut there.

Pop the camber link ball cup and the toe ball cup off the C block.

Lean the C block towards you and pull the dog bone out of the diff cup.

Rotate you diff so that the slot in the diff is at pointing at 9 o'clock - 3 o'clock.
Install the spring, the end you cut, into the diff cup with the cut end pointing to 12 0'clock or 6 O'clock.
Reinstall the dog bone and snap your links back in place.
Do this for both sides.

HPI Sprint 2 Mods - Making a silk purse from a sow's ear.-springinstalledinfrontcopy.jpg


REAR SPRING
You are only going to use the center of the spring.

Take one spring.
Cut off both ends close to the tightly wound coils.

Rotate the spring so the a cut end is facing up.
Counting that half coil, count 2-1/2 half coils and cut.
You have 3 coils total counting the 2 half coils.
Repeat this for the piece you have left.

Pop the camber link ball cup off the hub.
Lean the hub towards you and pull the dog bone out of the diff cup.

Rotate you diff so that the slot in the diff is at pointing at 9 o'clock - 3 o'clock.
Install the spring into the diff cup with either cut end pointing to 12 0'clock or 6 O'clock.
Reinstall the dog bone and snap your camber link back in place.
Do this for both sides

HPI Sprint 2 Mods - Making a silk purse from a sow's ear.-springinstalledinrearcopy.jpg




Schrödinger's Cat

In the world of quantum mechanics, the laws of physics that are familiar from the everyday world no longer work. Instead, events are governed by probabilities.

A radioactive atom, for example, might decay, emitting an electron, or it might not. It is possible to set up an experiment in such a way that there is a precise fifty-fifty chance that one of the atoms in a lump of radioactive material will decay in a certain time and that a detector will register the decay if it does happen.

Schrödinger, as upset as Einstein about the implications of quantum theory, tried to show the absurdity of these implications by imagining such an experiment set up in a closed room, or box, which also contains a live cat and a phial of poison, so arranged that if the radioactive decay does occur then the poison container is broken and the cat dies.

In the everyday world, there is a fifty-fifty chance that the cat will be killed, and without looking inside the box we can say, quite happily, that the cat inside is either dead or alive. But now we encounter the strangeness of the quantum world.

According to the theory, neither of the two possibilities open to the radioactive material, and therefore to the cat, has any reality unless it is observed.

The atomic decay has neither happened nor not happened, the cat has neither been killed nor not killed, until we look inside the box.

Theorists who accept the pure version of quantum mechanics say that the cat exists in some indeterminate state, neither dead nor alive, until an observer looks into the box to see how things are getting on.

Nothing is real unless it is observed.

Last edited by Marv; 11-10-2012 at 05:21 PM.
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Old 10-12-2012, 11:34 AM   #125
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"Schrödinger's Cat

In the world of quantum mechanics, the laws of physics that are familiar from the everyday world no longer work. Instead, events are governed by probabilities.

A radioactive atom, for example, might decay, emitting an electron, or it might not. It is possible to set up an experiment in such a way that there is a precise fifty-fifty chance that one of the atoms in a lump of radioactive material will decay in a certain time and that a detector will register the decay if it does happen.

Schrödinger, as upset as Einstein about the implications of quantum theory, tried to show the absurdity of these implications by imagining such an experiment set up in a closed room, or box, which also contains a live cat and a phial of poison, so arranged that if the radioactive decay does occur then the poison container is broken and the cat dies.

In the everyday world, there is a fifty-fifty chance that the cat will be killed, and without looking inside the box we can say, quite happily, that the cat inside is either dead or alive. But now we encounter the strangeness of the quantum world.

According to the theory, neither of the two possibilities open to the radioactive material, and therefore to the cat, has any reality unless it is observed.

The atomic decay has neither happened nor not happened, the cat has neither been killed nor not killed, until we look inside the box.

Theorists who accept the pure version of quantum mechanics say that the cat exists in some indeterminate state, neither dead nor alive, until an observer looks into the box to see how things are getting on.

Nothing is real unless it is observed."

Hence the reply "Pics, or it didn't happen." We all seem to be a bunch of quantum physicists... Poor cat, stuck in stasis until observed...
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Old 10-12-2012, 03:58 PM   #126
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Excellent way to improvise, adapt and overcome, Vostok!

Thanks for adding your "americanized" (LOL) version!
I'm not 100% happy with how it turned out, it did get rid of some slop but it's not perfect, but I have another idea that I'm going to try once I get the proper metric hardware. It's still a viable option for anyone who can't get a hold of metric hardware, though.

The biggest issue is the nuts are slightly too big since #6-32 is somewhere between M3 and M4, so the corners of the hex catch on the inside of the bellcrank whenever you try to put pressure on the assembly. It helps a little, but not enough for my taste because you don't get anywhere near the bearing races.
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Old 10-15-2012, 11:45 AM   #127
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Originally Posted by Marv View Post
Optional Left Crank Mod / Slop Fix

NEEDED
1 - M3x35mm Flat Head Phillips Screw
3 - M3 Lock Nuts - Dubro #2101
Ruler

Remove the upper deck.
Remove the left crank assembly.
Remove the shaft.
Measure the distance from the bottom of the shaft to the step that the bearing sits on = this is the height of the second screw you will be installing.

Run the M3x35mm Flat Head Phillips Screw up through the chassis and install a M3 Lock Nut as shown (tapered end facing up) - Tighten it down good.

Install another M3 Lock Nut as shown (tapered end face up).
The position of this lock nut on the screw will determine the height of the crank.
Install the left crank assembly, with bearings still in place.
Install the last M3 Lock Nut as shown (tapered end facing down).

Click thumbnail for larger picture

Attachment 938775

Installing the lock nuts as shown brings pressure on the inner races of the bearings.
Proper adjustment = reduced slop and wobble in the left crank assembly.

DO NOT OVER TIGHTEN the top lock nut!

Adjust the top lock nut so that the bearing slop is nil and the crank doesn't bind when moved through it's operating range.

Reinstall upper deck and linkage. You'll notice that the M3x35mm screw comes up through the upper deck hole. This is not a bad thing - on the offside chance that the first lock nut should come loose while your driving (highly improbable) the extra length coming up through the deck will help stabilize the assembly somewhat till repairs can be made.

When compared to the previously posted left crank mod, this one is cheaper & tighter.


NOTE: The FRONT C HUB / KNUCKLE / CONTROL ARM & REAR HUB slop fixes are almost complete and will be posted soon.
OK, I finally got all the parts for this and I'm really happy with how it came out.

The biggest issue I had with this mod is that the M3 screw comes nowhere near the races of the bearings, so you get slop where the bearings can move laterally on the screw, and I also wanted to get the arm on roughly the same plane as the right side, and finally, make something as secure and adjustable as possible.

What you will need:

1x M3x35 or 40 countersunk flat head screw (Philips or Hex)
1x M3 plain nut
2x M3 Locknuts (Dobro, same as above)
2x HPI M3 Aluminum washers (HPI part # Z816)
Electrical tape

You will see that I have the GPM aluminum bell crank set, this mod should work with the stock plastic though I have not tested it. I used the 40mm long screw, 35mm would work just fine.

Take off the top plate and take apart your left bell crank as detailed above.

Thread on the lock nut and then a plain M3 nut and then the aluminum washer as shown below:





This puts the bell crank at only a millimeter or so higher than with the stock shaft. As shown in the pictures above, you want to wrap about 1-2 turns of electrical tape on to the screw, just enough to take up the distance between the screw and the bearing race. Cut the electrical tape in half before you wrap and then use an Xacto knife to adjust the height once it's on, you only want it about 1mm or so higher than both bearings stacked together or the top parts won't fit.

Put the bell crank arm and top bearing back on and then slide on another washer:



Then bolt down with another lock nut:



Make sure you don't bolt down too hard, getting the pressure right is largely up to feel. I had it just loose enough the arm swung freely but then when I assembled everything back together, it was too loose. Crank it down too tight, though and you can blow your servo. So just play with the pressure until you get a good mix of a small amount of slop but a servo that doesn't jam and returns to zero well.

Done!



With this setup I actually was able to back the servo saver almost all the way loose so that the saver can actually do it's job and now I have only a teeny bit of slop, no major toe changes when accelerating like before. The spacers I feel give a more consistent pressure on the bearings. When you play with the arm alone now you can feel the action of the bearings, nothing else.

Another option is to use the stock metal bearing post but cutting off the spacer at the bottom and the e-clip groove at the top and then drilling it out. It appears to be threaded all the way through. I'm going to be trying this when I get a chance since it will be a little more secure than with electrical tape.
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Old 10-15-2012, 11:50 AM   #128
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Hi Marv.

Do you have the reference number of the RPM's ball cup that you used in your car? And the dimensions of then?

Thank you

Marcelo
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Old 10-15-2012, 01:25 PM   #129
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Default RPM BALL CUPS

Quote:
Originally Posted by MARCELO CAMPOS View Post
Hi Marv.

Do you have the reference number of the RPM's ball cup that you used in your car? And the dimensions of then?

Thank you

Marcelo
http://www.rpmrcproducts.com/product...c/steering.htm



Heavy Duty Rod Ends

When it comes to rod ends, we are the basis for comparison!
Our rod ends have oversized hexes and our ball cups are molded to the strictest of tolerances.
Each rod end is molded from our blend of extremely tough, bulletproof nylons. If you’re tired of popping ball cups and breaking rod ends, RPM rod ends are the solution!
RPM rod ends fit all 1/10th scale HPI 4.3mm ballstuds* and all 1/10th scale Associated & Losi ball-studs.
Like all of our products, RPM rod ends are guaranteed not to break!
Available in Bold Black, Dyeable White, Yellow, Blue, & Purple!

Tech Notes -
HPI owners: RPM Rod Ends will not work in conjunction with newer 4.8mm ball studs such as those found on the HPI Blitz and Firestorm line of vehicles.

They will only work with HPI 4.3mm ball studs.

73372 Heavy Duty Rod Ends (12) 4-40 (Black)
73375 Heavy Duty Rod Ends (12) 4-40 - Blue
73377 Heavy Duty Rod Ends (12) 4-40 - Yellow
73378 Heavy Duty Rod Ends (12) 4-40 - Purple
73381 Heavy Duty Rod Ends (12) 4-40 (White)

Suggested Retail $4.95 / set of 12
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Old 10-15-2012, 01:38 PM   #130
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Vostok 7,

EXCELLENT idea adding the HPI Z816 spacers!

Thanks for posting that with the pics

Just replace the two OEM bearings with - 3x8x3 bearings (eBay).

My bad for not including that in post #17 - It's been updated.
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Old 10-15-2012, 01:43 PM   #131
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Originally Posted by Marv View Post
Vostok 7,

EXCELLENT idea adding the HPI Z816 spacers!

Thanks for posting that with the pics

Just replace the two OEM bearings with - 3x8x3 Bearings.

My bad for not including that in post #17 - It's been updated.
Well now, I'll have to try that. Better than cutting up my stock bearing shaft or using tape. Thanks!
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Old 10-15-2012, 01:49 PM   #132
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Originally Posted by Vostok 7 View Post
Well now, I'll have to try that. Better than cutting up my stock bearing shaft or using tape. Thanks!
Yeah, my bad... I try to cover all the bases.

"I've got a condition. I get confused sometimes."
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Old 10-15-2012, 01:56 PM   #133
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I went with a ceramic hybrid = A waste of $ (IMO).
They aren't any tighter than the OEM's.

Next time around I might try a sealed bearing.
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Old 10-15-2012, 04:44 PM   #134
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Quote:
Originally Posted by Marv View Post
http://www.rpmrcproducts.com/product...c/steering.htm



Heavy Duty Rod Ends

When it comes to rod ends, we are the basis for comparison!
Our rod ends have oversized hexes and our ball cups are molded to the strictest of tolerances.
Each rod end is molded from our blend of extremely tough, bulletproof nylons. If you’re tired of popping ball cups and breaking rod ends, RPM rod ends are the solution!
RPM rod ends fit all 1/10th scale HPI 4.3mm ballstuds* and all 1/10th scale Associated & Losi ball-studs.
Like all of our products, RPM rod ends are guaranteed not to break!
Available in Bold Black, Dyeable White, Yellow, Blue, & Purple!

Tech Notes -
HPI owners: RPM Rod Ends will not work in conjunction with newer 4.8mm ball studs such as those found on the HPI Blitz and Firestorm line of vehicles.

They will only work with HPI 4.3mm ball studs.

73372 Heavy Duty Rod Ends (12) 4-40 (Black)
73375 Heavy Duty Rod Ends (12) 4-40 - Blue
73377 Heavy Duty Rod Ends (12) 4-40 - Yellow
73378 Heavy Duty Rod Ends (12) 4-40 - Purple
73381 Heavy Duty Rod Ends (12) 4-40 (White)

Suggested Retail $4.95 / set of 12
First of all, THANK YOU!!!

Marv the studs that you use was the blue one is that correct?

I still overhauling my sprint chassis. The old owner was very very relapse with this car.
Here some photos:




I'll change the bearings and suspension arms

This was the situation when i opened the rear diff:



Look at the diff bearings:



This car is a matter of honor for me now....

MArcelo

Last edited by MARCELO CAMPOS; 11-02-2012 at 06:28 AM.
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Old 10-16-2012, 09:55 PM   #135
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That's the old style bulk head - the rear one - you might consider upgrading it.




Your diff has no guts!!!




There's a guy on eBay that sells a complete, new (pulled from a never ran car) diff for about $13.00 shipped.


That looks like a regular screw in that link - ya need some ball studs, Marc.

And the rod itself looks like it's been changed.




Link for the S2 manual at HPI = http://www.hpiracing.com/graphics/in...130/106130.pdf

Last edited by Marv; 10-17-2012 at 06:14 PM.
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