Runner Boomerang refurbishment

[kontemax 1780]

NOTE: Currently I'm replacing the hosting for the pictures.
This means that I must replace all the pictures of the thread. I will need several time to do it so, when you will find a missing picture please be patien. Matter of time and I will replace it. Thanks and sorry for the inconvenience.

Hi folks,

today I decided to open the Boomerang gearboxes and make some refurbishment.

Short description of the car: Vintage Boomerang

Status: Runner

Modifications: carbon fibre sway bar stays, carbon fibre rear dampers tower, carbon fibre front damper mounts, carbon fibre rear arms brace, alloy rear lower arms, locked battery door, battery quick release, full ball bearings, cnc machined ball beared steering bar, Hi-Torque BB steering servo, small bumper, front arm brace, hard propeller shaft, steel pinion gear, front and rear ball differentials, front and rear universal joints, alloy dampers with Titanium Nitride shafts, speed disk wheels, battered body.

 

The general conditions of the car are bad because it had an hard life on the tracks.

This Boomerang is equipped with a 12 turns brushed motor, the car is fast and it crashed many times.

Many parts will be broken for sure and I'm a little bit scared from what I will find inside the gearboxes.

I never made manteinance on this model because it's hard to disassemble due the ball differentials and the locked battery door.

I decided to do this job because the rear ball differential doesn't turn smooth and I don't want to ruin it.

The car was never cleaned inside nor outside. It's time to do it.

Max

[matman 1500]

I love the mods you have on this & would like too see them more .

I had a 5.5 BL system in MY runner Boomerang & that was fine .

So i'm sure it will be fine .

Ball diffs you say , would like to get some of them & did you make the carbon stuff your self ?.

Alloy rear arms ? Where did you get them .

As you know i love the boomerang , so i am going to to be watching this thread close .

So bring on the pic's M8 .

[Avante2001R 305]

Ball diffs? I thought they only came with bevel diffs? Or did someone release a ball diff kit?

[matman 1500]

Ball diffs? I thought they only came with bevel diffs? Or did someone release a ball diff kit?

Yer !! thorp did & another one as well << can't remember .

Same as blackfoot / Fox , but with dog bone cups & some shims for spacing .

I think hotshot ball diffs came out from thorp as hotshot ball diffs ? . << & they of course

are the same as boomer .

NOT cheap sadly .

[Quandry 378]

Very nice machine Max! interested to see how your refurb goes

[Plopes 139]

Hi Max, Looking forward to this interesting re-build.

[kontemax 1780]

Starting to disassemble the rear Boomerang gearbox.

The first items to disassemble are the rear dampers.

I mounted some Duratrax dampers on this model. I never refurbished them and they are still very smooth.

These shocks have a very long extension. Too much extension so I needed to limit it to the correct lenght. Note the dust everywhere.

Dust and broken parts. The yellow wire you see is a brass wire that I used to sew and keep all together the broken parts. The rear gearbox is one of the most ruined parts.

The dampers disassembled.

Note the different left/right set up.

These dampers are so sensitive to the set up that the right damper needed to be stiffer than left one. Why?

Because there's the motor weight on the right side of the chassis.

Max

[kontemax 1780]

More picture of the devastation of my Boomerang runner.

More brass wires. There is no single plastic part on this model that is not repaired.

Here you can see what I did with the battery door of my Boomerang.

I believe that the Boomerang has the best chassis of the Hot Shot series but the battery door is its weak point. Many forces are loaded on this part that is bad designed and weak.

The Tamiya engineers did understand it too late and decided to correct the problem only with the Thunder Shot series.

Anyway the problem remains on every Boomerang/Winger/Super Sabre owner so I decided to solve it by myself inthe same way it was solved on the Thunder Shot series.

I decided that the battery door and the chassis must be the same object so I locked them forever.

To obtain this result I built this aluminum part that perfectly fits the rear gearbox and is screwed to the rear end.

In the other side the door is screwed to the chassis on this aluminum part.

The result is a solid and stiffer chassis with a similar concept of the Thunder Shot one.

Checking the model I found more and more cracks and brass wires all around.

I did decide to replace only the rear gearbox but now I'm thinking to replace the front one also.

The model, as I said, had an hard like on the tracks but I must also say that it was assembled with old used parts.

Stay tuned.

Max

[zomboided 374]

Be interesting to see this wreck all get brought back together...keep the pictures coming Max!

[kontemax 1780]

Ahahah!

Keep in mind that this will remain a runner so I will always use used dented and scratched parts to restore it.

When I see all these glossy plastics I feel bad to ruin them.

For this reason all my runners are used cars and not new built cars.

Infact I'm searching for used plastic parts to replace the broken ones. So this will be a cheap and functional restoring job, waiting for the spring.

This car will come back to the tracks soon!

Max

Be interesting to see this wreck all get brought back together...keep the pictures coming Max!

[kontemax 1780]

Ok folks,

more pictures as request!

The images speak themself. The model is dusty and needs a good refurbishment job. Many failures all around. The messy part, as I said, is the rear gearbox, as every 4wd model I suppose.

You can see here one of the worst damage. One rear side mount, that one above the motor, is broken and it is missing a bit.

Probably because the motor is too hot, maybe a little bit over powered for the old chassis and old battered plastic parts.

In the next picture you see an aborted tentative to make a brace like the one I made on the DF-01 chassis. You can see it pointed by the red arrow.

More brass wire.

Instead of the previous brace, this brace has been done, that time I was not lazy, and probably it saved the rear gearbox. A must to have in my opinion.

Compulsory picture of the aluminum rear arms:

What is a runner without universals?

Thanks to these universals, to the hard propeller shaft and the ball differentials this Boomerang is not noisy and feels smooth on the track.

And here the powerplant: a LRP 12x2 turns. The car is fast and the 13T steel pinion gear is obligatory. I believe it is yet too big so the next gearbox will be modified to use a 12T steel pinion gear.

That's all for the moment. Hope you like the pictures.

Max

[kontemax 1780]

New pictures are arriving!

These days I'm a little bit free from the job so I'm going ahead with the projects.

Finally here is the rear gearbox open so you will see this mythical ball differential.

Another picture of the super worn out rear gearbox:

The first modification I want to display is the transparent window that I made to check the pinion gear:

Do you see the screw inside the diff outdrive? Yes, this ball diff is not a Thorp, I don't know what brand it is but I can set up it from outside like the modern ones.

Finally the gearbox is open. My idea of the sponge seal works. Do you see the dust inside?

And let me introduce you the Graal!

Yes, it is a brown/red gear, don't ask me why, I don't know.

The diff plate and the spur gear (that is a little bit worn out too):

Cooked grease all around:

That's all at the moment.

I'm working at the 12T pinion gear modification today, so I will post news soon.

Max

[kontemax 1780]

This is a gear ratio chart that I calculated counting the gear teeth.

Maybe someone needs it so here is it:

17T = 7.67

16T = 8.15

15T = 8.70

14T = 9.32

13T = 10.04

12T = 10.87

I made the modification for the 12T pinion gear on the old battered gearbox. It works but I noticed that I lost the 12T pinion gear from my spares so I must wait and buy another one. I'm disappointed.

Max

[kontemax 1780]

Ok mates,

here some progress on my resto/refurbishment job.
The ball differential has been all disassembled and cleaned:



I don't understand what kind of material is this but it works:



This is C40 Steel probably. Very strong.



And this is the currency that ruined my country, Spain and destroyed Greece.



Let's go on. First thing to do in this refurbishment job is to replace the gearbox that, as you seen, is totally destroyed. Digging in my part boxes I found my first rear gearbox from 1986 that I replaced at the time because I broke the shock tower mount. I remember I made a big jump on concrete, the car did it without problems, landed on all four wheels and survived but the landing was really hard and I broke that little black piece that keep the tower mount in place. I replaced the gearbox just to discover that this part was too weak and prone to breakage. In fact I broke it again and I did invent, with my daddy, a definitive solution that I will show you in the next pictures. So, apart this little breakage, this gearbox is almost new and intact from the past. Now it will work again. Here the parts.



Mandatory picture of yellow lettering. It is scientifically proven that with this lettering the model is 12% faster on the track.



This is the broken part. One side only.



The old one were broke both sides but my solution resolved the problem. And here is the solution:



A little steel plate with a 3 mm nut soldered on.



Looks ugly but it works.





Max

[kontemax 1780]

It's time to make my modification to the rear gearbox to allow the use of a smaller pinion gear. The Boomerang gearbox allows 0.8 module pinion gears from 13 teeth to 17 teeth.

13 teeth give a gear ratio of 1:10 circa that is a good gear ratio for a mild motor of the 80ies. I used a very hot motor on this car so I always needed a smaller pinion gear to obtain an higher gear ratio.

The rear gearbox has some room inside to mount a 12 teeth pinion gear so I decided to do it. The motor position on this gearbox is decided by the position of four 1 mm thick steel plates. These ones:

I decided that my Boomerang will have five plates instead of four:

Look at the smaller pinion gear.

Here the five plates in place (marked with the white arrow).

I made this modification on the old gearbox (you can also see other failures marked with other arrows). If the modification will not work I will not ruin the spare gearbox. Then I close the gearbox partially mounted just to test the modification.

It works perfectly. Now I can open again the gearbox and repeat the operation on the new parts.

Before to mount the gearbox I must do another little modification again. I must countersink the lower screw to hide the screw head and make clearance for the battery door lock.

On the other side I rounded a 3 mm lock nut. Then I dented it and put it inside the screw hole.

Done!

Max

[kontemax 1780]

I forgot to answer you all, it's time to do it:

Yes, ball differentials, I found them on ebay some time ago but I don't know the brand. They could be handmade, I don't know.

I made the carbon stuff by myself.

I got the alloy rear arms on ebay also, some time ago. They are machined but "hand made". I refined some parts of them with my hands, to make clearance for the rear dampers for example.

I made many pictures for this thread, I hope they are enough.

Max

Ball diffs you say , would like to get some of them & did you make the carbon stuff your self ?.
Alloy rear arms ? Where did you get them .
As you know i love the boomerang , so i am going to to be watching this thread close .
So bring on the pic's M8 .

[kontemax 1780]

Yes, ball diffs.

Believe me, they make the difference on the track. The car is more balanced, has more traction and has no more so oversteer as the original Boomerang.

The Hot Shot mechanics makes the cars like drifters on the rough terrain. Fun to drive but not so easy to be fast.

Max

Ball diffs? I thought they only came with bevel diffs? Or did someone release a ball diff kit?

[Avante2001R 305]

Would be awesome if ball diffs were readily available or someone would make them, but I have bought enough bits to build a another boomerang and replenish my vintage one. I will start on it soon.

One question, looking at the out drives on the re re they appear smaller like the manta ray/thundershot, is it possible thundershot ujs or the new CVD from DF03?

BTW saw a crazy boomerang on YT running brushless 8.5 T and lipo, the thing looked ballistic! Didn't realise they could handle the power and not strip gears.

[matman 1500]

Would be awesome if ball diffs were readily available or someone would make them, but I have bought enough bits to build a another boomerang and replenish my vintage one. I will start on it soon.

One question, looking at the out drives on the re re they appear smaller like the manta ray/thundershot, is it possible thundershot ujs or the new CVD from DF03?

BTW saw a crazy boomerang on YT running brushless 8.5 T and lipo, the thing looked ballistic! Didn't realise they could handle the power and not strip gears.

I had run a 5.5 BL in My boomerang & it was nut's .

DF02 ? / DF03 & i think it's DT02 fit , Kontemax will tell ya if i have got it right . I must have to get some my self , HAHA

I don't have any in my runner / racer ... What was i thinking

[kontemax 1780]

Absolutelly yes. This Boomerang has the vintage half shafts and drive cups.

They are 11 mm of external diameter.

The re release Boomerang has modern drive cups (10 mm), just like the Terra Scorcher, Top Force etc etc.

You can mount modern DT02/DF03 CVD shafts.

Max

One question, looking at the out drives on the re re they appear smaller like the manta ray/thundershot, is it possible thundershot ujs or the new CVD from DF03?

[kontemax 1780]

Ok, now a quick check for the rear tower mount.

It perfectly fits.

It is perfectly calculated to not touch the spur gear teeth. With this plate the shock tower doesn't move and can support bigger loads.

Once the two shells are closed it only needs to be tightened with a 2 mm allen key.

The next step is to reassemble the gearbox. I use thrust bearings on my Boomerang.

You did see how the sponge seal works. The model was never cleaned and there was no dust inside. So I will do the job again with the new gearbox. I only need some glue and some thin sponge. I cut the sponge in thin slices and I glued them onto one of the gearbox shells. Then I trimmed them to reduce the excess.

Bevel gear and bearings in place.

One drive cup before the gears.

Now the gears, included the red ball diff gear.

Then the balls and the shock tower mount.

Close picture of the tower mount modification. Thanks dad!

The opposite drive cup and the ball pressure plate.

Everything closed. The flame of a lighter has been useful to eliminate the excessive sponge from outside the gearbox.

That's all for today.

Max

[kontemax 1780]

Do you see these little balls?

The allen key is 2 mm. Just to explain better:

Ok, I must glue with grease these micro balls to the screw like this:

And put everything inside this hole into the drive cup...

This is a watchmaker or a blaster job.

With many sweat of the brow and great tension I did it and now the rear gearbox with the internal ball differential is closed. The main job is done.

This gearbox is 28 years old and, as I said, it was the original one of my Boomerang. The yellow lettering pictures are mandatory.

Note the drive shaft axle.

This is another modification I did in unsuspected times, many years before the re releases. The original thin wire main shaft was a **** and I decided to replace it with a stronger one. The example was the TA01 hop up shaft. All my shaft is scratch built.

Let's go to the motor. I decided to downgrade the motor from a 12T to a 17T. The car was insanely fast, too much for the lenght of my local track. You can see one of my refurbished rotors:

Do you see the white arrow? Please have a closer look to the commutator. This was a totally worn out rotor that a guy threw away at my local track. These commutators from the the early years of the century were soft like butter and wear 100 times faster than 80ies and 90ies commutators. I collected all of these worn out rotors for free and recreated the copper all around the commutators with the electrolytic copper plating system. My refurbished rotors are harder and don't wear. Often I decided to have a bigger diameter of the commutator, from the original 8/8,5 mm to 10 or 11 mm. This means a less angular momentum and less friction with the brushes and more contact surface with them. In fact my rebuilded rotors were faster than the original ones. I sold most of these rotors on the track, the people went crazy for them cause they were faster, they didn't wear and the bigger diameter did allow more turning of the rotor at the lathe.

This 17T is one of the 10 rotors I kept for my personal models.

The brushes are in good condition.

The motor finally closed. It was in good conditions.

And yes, I did it again, this time on the new gearbox. Five plates means 12 teeth pinion gear.

Gearbox finished.

Max

[matman 1500]

I used to do that to mine & rewire it to a lower turn .

I did play with the stock 540 & made that a 5 turn , Now that was funny ,

went fast , But the plastic end bell didn't last to long . But i was learning then ! .

This was back in the 80's ... When fire was normal ! > < I think !!

Thanks Max , some thing i forgot about & came to me when i was reading this . So thanks again M8 .

[kontemax 1780]

My faster motor is a 6 x 2 turns that I rewinded and balanced by my hands. It made something more than 68.000 rpm eheheheh! Never used on a model.

Max

[kontemax 1780]

Up for a mate that needs info about it.

Max