CRP/Turbo Scorpion Racer

[Hcp22]

Thanks Mark for the advice! So it’s the same roles as always that I have to consider for indoor carpet race. These taller uniformed tires make it trickier, both with the ride height and the grip. Back then we used sponge tires with a diameter of 70-75mm and no track bite was allowed.

I will do some more testing to day, to see where I stand in performance.

[mjtown]

Now I get to a difficult part for a 26 year old runner/racer, the tires! The Scorpion rims are 1.5” at the rear and 1.9” at the front. To find new tires could cost you a fortune and some time to find. And if you find some tires, they hard as “hockey pucks” (Swedish expression) and no god on the track!
A solution is 2.2” rims and modern tires, problems … some yes! Around 95 manufactures went from having bearings in the rims to have the bearings in the wheel axels at the front. But the old stile front rims are still produced, so this isn’t a problem. The rear rims are a different story, you have to do some modification on the Scorpion first before you can mount modern 2.2” rims.
The Scorpion drive washer is round and not a 12mm hex, and that’s what you need. I purchase ”HPI’s Racing Locking Hex Hub 12mm” and the some from AXIAL. The deferens between this two are the color. This is not the perfect solution, but still a solution that works. HPI has another type (more expensive and purple) that I will test later on ”HPI Aluminum Hex Hub Clamp Type 12mm” (Ordered).

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My attention is a 26 year old racer, so I didn’t chose 2.2” rims at this time. For the rear rims I have chosen Optima 1.6” and newly produced OT-30 tires from Jose in Spain. I even tried to mount on the Scorpion 1.5”, to my surprise it actually works fin on that rim to. The different between Scorpion’s SC-84 Sand Super and Optima’s OT-30 Sand Super is that the SC-84 is slightly wider than OT-30.

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At the front I have original 1.9 Scorpion rims and Amark tires still sold by CRP for $10.

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To be continued!

Hi Lars,

I've finished my Turbo Scorp build now, and I'll start a thread about it soon. In the meantime can you please answer a couple of questions about wheels and tyres?

I want to drive my car and race it, but I don't want to trash the original rims and tyres, because they're so rare. To run new design rims with hex drives I will need to use adaptors like your photo above. I don't quite understand how this works - is the hex hub in your photo attached mechanically to the axle, or does the friction between the original round drive washer and the new hex hub stop the rim from slipping on the axle?

Another option is to run Optima rims like the ones in your photo. I have never seen these though. Do the Optima rims use the same round drive washer as the Scorpion, or will I need the hex hub (like your photos)?

I guess that the final option is to run Optima OT-30 tyres on my Scorpion rims. I have found these photos (I'm sure that they're your photos!) with OT-30 on the left and SC-84 on the right:





Are those rims the size of those from the Turbo Scorpion? Are the tyres on the rims in the second photo - i.e. the shot from above? It looks like they will work pretty well!

One last thing... do you know where to get more of those Amark tyres?

[Hcp22]

I will try to sort out all your questions, and I will start with the simple one!
Yes, it’s OT-30 on the left, and Optima wheels have 12 millimeter hex.

Next up is the 12 millimeter hex: If you mount them as they are, they will slip. You will need to drill one hole on the opposite side of the “clamp screw” (alt A). Thread this hole and attach a set screw, this will be enough depending upon witch motor you will run. You can attach two set screws if you want to (alt B). I will do that on my 21st century Kyosho Beetle before I run it with the brushless 13.5T motor.

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Talking about set screws; you have to drill and thread two more holes to keep the frontend axel in place. Otherwise it will twist while landing after a jump!

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Now the wheels:
If you want race you’re Scorpion, you have to determine on witch level. But you always get better performance with modern tires. If you use modern tires you have to considering three things:
1. Lower the frontend and the rear by extending the shock towers 10-15 millimeters and 2-3 holes.
2. Mount a front sway bar, easy to bend one out of piano wire.
3. Make an adjustable motor plate.
This is because that modern tire has a larger diameter then original tires. And you should also consider widening the front with a CRP front axle.

I hope this answers your questions and I’m only glad if I can help you out in some way. And I’m rely curies to see your TS built.

[mjtown]

Thanks Lars!

I'm taking a slightly different approach with my build. The car is one that I purchased as a kid in 1988, and I am trying to maintain the 'original' appearance of the Turbo Scorpion, and only using genuine original hop ups (i.e. vintage CRP items etc). I am also happy to make modifications that could have been done in the 80's, but I would prefer not to use new wheels etc. I'm trying to keep it in the style of a racer built in the 80's because I want to do vintage racing where I live in Australia (Adelaide).

Drilling holes and using set screws to hold the front axle sounds like a great idea. Drilling a hole isn't too hard as my uncle has a drill press, but how do you thread the hole? What size drill bit and set screw have you used? I wonder whether strong Loctite would work instead?

Are you happy with the fit of the OT-30 on Turbo Scorpion sized rear rims? Do you think OT-30 on the Scorpion rims will be an adequate solution? It would save me from messing around with hex drives, and I would get to preserve the original look of the car, especially with the 'Sand Super' label on the side (which I have always loved!).

If I do need to use hex drives and original Optima wheels, do you think that these clamp types would be ok? They are a Yeah Racing product.

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Yeah Racing Hex Clamp.jpg (16.03 KiB) Viewed 3132 times

They may grip the axle enough as I'm not going too hard with my motor and electrics - the setup is vintage Le Mans 240SB or Spa 480WT motor with 7.2V NiMH battery. Original design rotary speed control with optional 4 speed instead of the original 3 speed (very vintage as you can see).

I'll start a new topic on my build, but here is the list of my revisions from original spec:

CRP front bumper
CRP front suspension bar
CRP rear suspension mounts
CRP brass counter gear
CRP rear CV axles
CRP skid pan
New silicon copper cables
Deans connectors instead of Tamiya type connectors
Handmade solid silver connectors to brass screws that pass through body tub, and from speed controller to motor cable.
Gold plated connectors to motor - from an audio supplier
Original Kyosho Option House gold shocks front and rear (I had to make front towers from aluminium plate - 6mm longer)
Original optional resistor set to give four forward speeds instead of three
New ball race bearings to entire drivetrain and all wheels
Reproduction body and decals from Marwan
SC-25 roll bar from an earlier Scorpion model - because I think it looks better, and suits the plastic roll cage shape better as it slopes forward at the top
Kyosho side/nerf bars for the Scorpion

I'll make up a front sway bar with piano wire and some brass tube at some stage, unless I can find a CRP sway bar at a reasonable price. I don't think I'll spend too much more money though - I have a couple of other hobbies (restoring and maintaining bikes and dj'ing) to maintain, and a family to support!!!

[Hcp22]

That’s understandable that you want to keep it within the 80”.
2.2” wheels appeared for the first time at the WC in Sidney -89! And I have to say that every modification you can think of can be used, maybe not LiPo! And perhaps not a brushless system, that came first a few years later in the 90”. Otherwise you can use any material that you can think of; at least that’s my opinion. I have seen some remarkable builds from Japan done in the 80” based on the Scorpion.

About the front axle, I don’t think Loctite will do the trick! I used 2.5 drill bit and M3 thread tap and M3 set screws.

The OT-30 will fit without any problem on Scorpion wheels as you can see in my pictures.
The Yeah 12mm hex will not work; they are only 5mm thick and want support a 3mm set screw. I will promise you, if you don’t use a set screw they will slip, I have tested. You have to use HPI or Axial 12mm hex made for a 4mm axle, the price is around $6 for a set of 4.

About the motors: I think you will burn up the 480WT if you don’t have the option to use a smaller pinion. The 240SB on the other hand will be perfect with the TS smallest pinion. On my runner I use LRP V10 2X19 brush motor with a standard pinion.
But before you run your TS you have to check so that all the gears aren’t to lose. Otherwise you will rip the gears eventually and that’s a promise. Use a needle file to make the holes oval on the motor plate towards the rear, you don’t have to do much, 0.5-0.7mm will do the trick (see picture). Then you get the option to tighten the gears, the same goes for the mounting holes for the motor. To tighten the diff against the inner gear is a bit trickier… I replaced the bushings with ball bearings and sins the ball bearings is 0.1-0.2mm smaller in diameter I was able to tighten it.

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You don’t need any brass tube for the sway bar, I made one and that one works as good as the CRP one i have.

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You got some nice hop-ups on your TS!

[mjtown]

Hi Lars,

This is great! Thankyou very much for your advice. I did buy the car in '88 and used it to race a mate in the park and backyard for a couple of years, but then it was damaged in a crash and put in a box and forgotten until last year, so I am new to all of this in a way. I certainly wasn't racing it properly back then. I did get the 480WT from him then though - I can't remember how. It seemed to work ok then, but then again I wasn't flogging it, and the batteries were 1200mah, not 5000mah like I have now! At any rate, thankyou VERY much, this is all very helpful.

I reckon I'll stick to the TS rims but use the OT-30 if I can't find SC-84 rubber for them. I reckon I will drill and screw the front bar though. Great idea.

With regard to the motors, do you mean that the 480WT is a higher power motor than the 240SB? I'm happy to leave the 480 on the shelf for a while until I get a CRP adjustable motor plate so that a smaller pinion can be used.

When you say "tighten the gears", do you mean slot the holes to mount the motor plate and then slide the motor plate towards the front of the car so that the 'centre gear' in the gearbox is hard up against the counter gear? Similarly, do you mean slot the holes for mounting the motor and then slide the motor along the motor plate towards the front of the car so that the pinion is hard up against the 'centre gear' - i.e. no slack in the system? That's all fairly easy - file or Dremel.

I have replaced all of the bushings with ball bearings - even one the 'centre gear' by replacing it with some non-flanged bearings (three next to each other on the stub axle between the motor plate and gearbox cover).

With regard to the inner gear, is it best to fasten it to the counter gear shaft so that there is no 'play' in the shaft? If I do that then only part of the face of the differential outer gear engages the inner gear, whereas if I move the inner gear along the counter gear shaft so that it is always in contact with the entire face of the differential gear then that shaft is free to move 'along it's length' from left to right a bit - i.e. 'across the car'. I don't think that it is too much of an issue, and I think that it is better to spread the drivetrain forces across as large an area as possible, even if that means that a shaft can move laterally a bit, but I could be wrong!

One thing, did you find that the CRP rear drive shaft on the right-hand side was too long for the Turbo Scorpion? I found that when the right-hand rear suspension was 'compressed', the 'dog bone' end of the drive shaft would push all of the way to the end of the drive cup, so much so that it prevented the suspension from moving through it's entire range of movement. If I released the set screw in the CV joint and moved the shaft towards the axle so that the dog bone only just touched the end of the drive cup, then the other end would foul with the inside of the CV joint. To make it work I had to get the Dremel out and grind about one millimetre off of the end that clamps into the CV joint. It works well now, but I shredded a ball bearing in the rear axle due to vibration! . I think that the TS gearbox is slightly asymmetrical to accomodate the differential, which was new for the TS, leaving very slightly less distance between the drive cup and axle on the right-hand side. I guess that this isn't noticable if you use the standard dog bones. The other obvious difference with the TS gearbox is that there are three screw holes to mount the rear suspension towers, presumably to stiffen the rear end. Generations 1-5 of the Scorpion only had two screw fixings there. Generation 5 & 6 (i.e. Turbo Scorpion) had three, so there were some substantial changes to the rear end. See http://vintagekyosho.com/?page_id=588 for some interesting narrative regarding the differences with the Turbo Scorpion.

[mjtown]

Here's my beastie... finally resurrected

[Hcp22]

The 240SB is much more suitable for the TS, but that’s just my opinion. I might was too hasty in my judgment, but ther is lots of guys that can tell you the deferens between toes tow motors.

You have understand me right about the gears, but not too tight!!! They should still run freely.

I had experience the same with my CRP CVD’s.

That’s a sharp looking TS you have, and I like that you use a mechanical sped control!

[mjtown]

Nice one! Thanks Lars

[Hcp22]

Some update on my Turbo Scorpion runner…

We have a Swedish vintage indoor carpet race coming up in the end of March.
I think will entry the race with my Scorpion; my problem is that I never raced the Scorpion before except against my friends at a backyard way back. In -87 I took my TS to the local club and run it once… The day after I purchased Schumacher CAT…

At first I thought to take it easy and have fun, “it’s just a 5 lap speed race”… But after I while the old racer was popping up on my shoulder telling me to start preparing the old car...

So I got myself a new LRP V10 2X17 with a soft torque and a high top end speed brunched motor. And a set of slicks on 2.2” HPI wheels for the event. Last week I did the first testing, but ran in to some trouble immediately… It over steered in to the corner and under steered out. The ride height was too high that resulted in that the car was tripping over the front wheel. So this weekend I made a pair of extended front shock tower, this allowed me to lower the frontend with about 15mm. I have also made a new slightly higher wing mount and a bigger wing.

Hopefully these mods will help me to keep the car on its wheels. There is huge deferens between a car from 88-89 compared with the TS from 85-86. The TS front track is 200mm and rear is 230mm compared with 250mm newer car. I have mange to increase the front track width with CRP arm shaft with 14mm to 214mm. So you can’t expect to go as fast with old narrow TS as you can do with over an inch wider car.

So if you have any tips and tricks to increase the performance on this 27 years old racer I will be grateful!

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This is a small update how my TS performed under race conditions at the Swedish vintage race held two weeks ago. First of all, the driver (me) need more driving practice…

We drove a 5 lap speed race qualification and a 10 lap final. In the final there was a mix of different cars and classes. One RC12, one Optima Pro, one MID Optima LWB, one Tamiya FWD Alfa 156, one RC10 and my TS in the final.

It all started well, I took the start and held it for a lap, and then I had to let the RC12 pass. ½ a lap later the MID past to… After 4-5 laps I lapped the RC10, then I tried to lap the Alfa but we tangled and my TS went upside down, so the Optima past me. I tried to regain the third spot but ones aging I had problem to lap that Alfa and after that it wasn’t time enough to catch that third placed Optima.

So overall the TS performed well and many eyebrows were razed, no one had expected that the TS were that fast and handle that good. But to the next year I have to build an extreme racing Scorpion the Japanese way. You wait and see “I will be back”

Or is it enough wit driver practice

[Coelacanth]

If I do need to use hex drives and original Optima wheels, do you think that these clamp types would be ok? They are a Yeah Racing product.

Yeah Racing Hex Clamp.jpg

They may grip the axle enough as I'm not going too hard with my motor and electrics - the setup is vintage Le Mans 240SB or Spa 480WT motor with 7.2V NiMH battery.

I actually did a similar mod with my friend's AYK Buffalo, which runs a Le Mans 360 Gold--a very torquey motor--and the hexes don't grip the axles firmly enough. They will slip with any motor producing a lot of torque. In his case, the only real solution was to find some HPI 5 x 50mm axles that are drilled for a cross-pin. The cross-pin goes through the axle and the hex fits onto it, this is the only guaranteed way to prevent your wheels from spinning.

I don't even think drilling a hole in the hex, adding a set screw, and tightening the set screw against a round axle will work for very long.

[Hcp22]

If I do need to use hex drives and original Optima wheels, do you think that these clamp types would be ok? They are a Yeah Racing product.

Yeah Racing Hex Clamp.jpg

They may grip the axle enough as I'm not going too hard with my motor and electrics - the setup is vintage Le Mans 240SB or Spa 480WT motor with 7.2V NiMH battery.

I actually did a similar mod with my friend's AYK Buffalo, which runs a Le Mans 360 Gold--a very torquey motor--and the hexes don't grip the axles firmly enough. They will slip with any motor producing a lot of torque. In his case, the only real solution was to find some HPI 5 x 50mm axles that are drilled for a cross-pin. The cross-pin goes through the axle and the hex fits onto it, this is the only guaranteed way to prevent your wheels from spinning.

I don't even think drilling a hole in the hex, adding a set screw, and tightening the set screw against a round axle will work for very long.

I drilled out for set screw and it works if the set screw is long enough so you can tighten it good. And if you file a small flat spot on the axel you can’t go wrong. Mine is holding up so far, but I have to agree that a cross pin is a far better and reliable solution!

[mjtown]

I did that the other day Lars - I dremeled a flat spot on the axle outboard of the tapered drive washers and the Axial 12mm hexes slot on nicely. I've found an old set of nib Raider rims to retain the vintage feel and it all seems to work very well

I can keep my original rims and tyres in one piece now - for shelf duties when we're all tucked in at home.

Great result with the racing by the way!

[mjtown]

Hey Lars, where did you get the little clips to secure your homemade sway bar to the chassis? Did you buy them somewhere or did you make your own? I'm playing around with a spare rear sway bar from an Optima OT-54 part that fits beautifully to the front of the TS, but I don't have anything to fix it to the chassis with.

[Hcp22]

The front sway bar is a CRP #1703, so that is not homemade (see the first page). I did make a homemade on my “21st Century Kyosho Beetle” (http://www.rc10talk.com/viewtopic.php?f=30&t=25900) and I used some old wing holder to hold the sway bar. But you can easily fold some thin aluminum sheet and drill a hole and mount it together with the bumper screws. You can attach the rear the same way if you can’t find the rare Dirt Burners #3006. I think you can use the same used for the Ultima sway bar at least at the front. They are similar to the Dirt Burners ones.