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Grasshopper II

This is the modified version of the original legendary Tamiya model. The Grasshopper was a best seller back in the 80's and many made their debut with it. Version 2 was released in 1988, quite soon after the original release (1984). Basically, the Grasshopper II is a Hornet chassis with a new bodyshell shared with the MadBull. On motor side, Grasshoppers 1 and 2 were given a Mabuchi 380 that can be easily upgraded to a 540: the buggy then becomes much faster. The suspension being very basic (simple springs), driving becomes even more approximative, but still grants great pleasure for a recreational use.

The name of the model refers to its very bouncy behavior on every surface. The rear dive train of the original model is fixed: as soon as a wheel goes on something, the whole drive train bounces. On version 2, the rear drive train oscillates like on the Hornet or the Lunch Box, but the spring suspension is not much more efficient either. In comparison, the Hornet rear drive train is very efficient with its hydraulic dampers being the only difference.

The Grasshopper family

The Grasshopper chassis can be found on several other models and many parts can be found on a wider ranger of models (like the gearbox/rear drive train on the Lunch Box and the Midnight Pumpkin).

58043 - The Grasshopper 58074 - Grasshopper II 58184 - Fighter Buggy RX 58275 - Mad Fighter

58045 - The Hornet 58124 - Super Hornet 58205 - Madbull In this model family, Grasshopper I & II are the basic models, the Hornet is an evolution (especially on the suspension and the Mabuchi 540 motor that replaces the 380) and the Super Hornet features every possible option to enhance its behavior. The chassis remains exactly the same on all these models. A few years later, Tamiya made changes on the chassis to release new models. The damper fit is different (oriented towards the inner chassis both at front and rear) and the rear drive train does now feature a central pivot axle. These two main evolutions have a direct and obvious consequence over the chassis behavior. Even if it remains strictly oriented to recreational use, the suspension works much better and can correctly deal with any playground surface. The typical bouncy behavior of the original chassis can almost be completely forgotten. Three models benefit from this enhanced chassis: the Fighter Buggy RX, the MadBull and the Mad Fighter presented above and on the left. This modified chassis is called a DT-01.

When it arrived

I got this model for peanuts. For the price, it could not be in mint condition. Obviously it was consequently used for what it was meant for: bashing. But overall, everything seems more or less OK. Some parts are disassembled and probably incomplete. Some photos at the box opening:

The box content Chassis overview A square tire (perfect for running in stairs ?) Bodyshell overview

Some parts including a new full set of Wild Willy 1 rims Zoom on the chassis The rear drive train (needs grease because it squeaks) Used, but nothing broken

At first sight, nothing seems broken or in need of serious repair. The few spare parts can't be enough to rebuild it completely, the transmitter may still work (to be checked), a battery pack is there but also needs to be checked, front tires need replacement, the 380 motor is there with it 10 tooth pinion but I will replace it with a 540 motor (18 tooth pinion). The mechanical speed controller will directly go to the trash as the resistor wires are burnt and melted.

Anyway, a full disassembly is needed to check up everything. But this restoration should be quite easy.

Reassembly and custom changes

The basic idea is to rebuild this model bringing a few modifications in order to enhance its performances and its behavior. The first step is to replace all the plastic bearings by ball bearings.

Replacement of the stock motor with a Mabuchi 540:
For this, the manual is very clear as it details the changes to make. In short, you have to remove the motor support, change the 10 tooth pinion by an 18 tooth and reassemble it directly onto the gearbox.
Integral review of the suspension system:
At the front, it just needed cleaning and greasing. At the rear, same operations plus the replacement of the springs because they were torn. So, nothing serious.
Replacement of the 4 wheels by a Mad Fighter set:
No problem at the front as it is a direct fit. At the rear however, the stock extensions have t be replaced by hex adaptors as the rims architecture is totally different. Tamiya anticipated this as these adaptors are available as reference 53913 - RC Frog 2005 Alum Wheel Adapt.

Replace the C7 extensions...

...with the hex adaptors...

...to get this result.

The stock support is broken and can't be repaired. So I made a "custom" one out of a servo axle directly screwed inside the chassis. It is screwed onto a support that is meant to fit the mechanical speedo plates. Then I inserted the antenna pipe into it where you normally find the servo head.

The antenna pipe is now positionned into the chassis instead of being in front of the rear wing (under the "L" of "Castrol" in the last photo).

For this one, I had to proceed differently from the Lunch Box, even if the base idea remains the same. Bad luck, there is no room enough between the chassis and the gearbox to place a damper there. Next problem: the Grasshopper rear side of the chassis is lower than the Lunch Box'. The total height doesn't allow you to fit a standard damper.

I got the idea from a model I saw in my friend Teamneogordini's collection: the Academy Roadrunner which is a Grasshopper "copy". More than a copy, Academy had directly fitted a third rear suspension system to handle the gearbox movement. What I made here is a direct adaptation of their system.

The first step is to cut the gearbox housing to insert a shock head (see the Lunch Box page for more details). On the second photo, you can see what is needed for this suspension system: one tie rod, one 3x10 screw, one Nilstop nut (diameter 3), two standard nuts (diameter 3, only 1 is shown), one U shape damper stay, and one pen spring (yes!). The third photo shows a small bit of plastic that is located at the rear of the chassis: cut it because it is right where the future damper goes.

Cut gearbox housing with the shock head

What's needed (1 nut is missing)

Plastic bit to be cut

Forth step: drill the chassis as high as possible in the exact line up of the damper head. To find the correct line up, the best is to screw the tie rod into the damper head. The best drill position is right under the top curved edge of the chassis. Then don't forget to insert the spring onto the tie rod and to cover it with the U shape stay.

Last steps: the system assembly. Screw the Nilstop nut until it touches the 3x10 screw head. Then screw the first standard 3mm nut until it touches the Nilstop nut. Inside the U shape stay, place the second 3mm standard nut, and from the inside of the chassis, screw the screw-Nilstop-nut into it. Screw it until the edge of the screw reaches the edge of the nut into the U shape stay.

Final step: from the inside of the chassis, unscrew the standard 3mm nut until it reaches the chassis so the system is correctly fitted. Then unscrew the Nilstop nut until it reaches the standard 3mm nut in order to strenghten the system.

Plastic bit cut and chassis drilled

The fix inside the chassis

The final result

With this system, we have a suspension solution for the gearbox movement. Not as efficient as the Lunch Box mod, but this is the only solution I could think of given the lack of room. Note that this mod can be directly adapted to the Hornet.

When I was searching the web for a suspension solution for the rear drive train, I found another solution made by TAZ-NZ, a member of TamiyaClub :

I think his solution is beautiful: he uses a cantilever system to convert the gearbox vertcial movement into an horizontal movement that is handled by the shock located inside the chassis.

However, this solution made me doubt:
1 - The shock is placed inside the chassis, thus it seriously reduces the available room for electronics (receiver and speedo). Especially because I use a Tamiya CPR-01 unit that is pretty big (it combines the receiver and the ESC).
2 - The gearbox movement can be brutal, especially with a 540 motor and on jump landings. Even more, the movement is rarely straight: to be straight, the 2 rear wheels have to reach the ground at the same time, the jump needs to be very well balanced (the buggy jumped in straight line) and the landing zone has to be perfectly flat. As far as my experience goes, these three conditions are very rare: they almost never occur at the same time.

For those two reasons, mainly the solution reliability, I chose to copy what Academy did on their Roadrunner.

The reassembly process is now finished. The Grasshopper is not in stock condition because I wanted to use as many spare parts I already had to limit the budget. The result is a very cheap buggy (20€ spent for parts, 10€ for the buggy itself), and it performs almost like my Hornet.

The above described 3rd rear shock setup didn't resist to the first run. After several weeks with no idea for a better system, I though about a new approach. The base mechanism remains the same and room constraints also remain the same.

Anyway, I came out with a new system that perfectly handled the first run. At least, it's a good start.

That is what is it about:

The 1st photo shows the shock head inserted into the gearbox case: no change so far.

Photo #2 shows this upper fixation. The U shape damper stay is still there, but differently oriented. This time, it squeezes 2 flanged tubes (thick ones): this is to ease the damper axle screw moves. The flanged tubes are inserted head to head so the U shape damper stay can maintain them. Also, the U shape stay holes are 3mm diameter whereas the flanged tubes external diameter is 4mm. The U shape stay holes have to be drilled for two reasons:
1. The flanged tube diameter is bigger than the U shape stay holes they have to get into.
2. The gearbox movement is not perfectly vertical: it is oriented backwards when the casing goes up. So the U shape stay holes need to be bigger to leave more room to the damper axle.

To built this up, you need to tear the U shape stay, insert the screw that will fix it to the chassis and then insert the two flanged tubes. Do not tighten back the U shape stay now.

Next step is to fix the U shape stay to the chassis. A spacer used to protect the chassis plastic and a Nilstop nut do the job. Now, we can tighten the U shape stay (if you did it before fixing it to the chassis, you can't screw it anymore). The final result is shown on photo #3.

Photo #4 a lateral view of the assembly. The damper axle is the one from the Grasshopper II front suspension. This axle is screwed into the damper head that is inserted into the gearbox casing. The damper spring also comes from the front suspension but you need to cut it to keep it soft enough. Between the top of the spring and the lower side of the U shape stay, insert the C11 part that also comes from the front suspension (C11 is used to maintain the upper side of the spring).

Yes, I did notice the Tamiya logo on the motor mount cache is reversed

This setup only has a silght problem: the motor hits the U shape stay when the rear drivetrain makes a perfectly linear move. Practically, this movement never happens when you drive because the lowest part of the gearbox attachment to the chassis needs to remain stuck while the rear part of the gearbox case compresses the rear dampers to the fullest.

The theorical suspension travel loss is about 3mm. In real driving conditions, with either a full or partial rear drivetrain oscillation, the loss is merely 1mm. Let's say it doesn't exist.

I used parts from the front suspension to built this third rear damper. The reason is easy to understand: I replaced the stock springs by friction dampers coming from my Citroën Xsara WRC. The benefit is quite impressive on the front drivetrain: it now stays up. But I kept the suspsension as soft as possible and the result is that the front drivetrain doesn't bounce anymore and directivity is tremedously enhanced.

With these new changes, the overall Grasshopper II behavior is even better: it is now very close to the MadBull's. Of course, it is still quite far from a modern competition buggy, but it is now much easier to control. Peebles and jumps are handled by the suspension and the Grasshopper doesn't bounce anymore like other stock chassis of its lineage.

First runs

The playground was the same as for the F-150: dust and dry puddles. The buggy overall behavior is very well illustrated by its name: it is a bouncy grasshopper. The speed and behavior are the same as with my Hornet, apart from a few details.

The tire set is also much more efficient than on my Hornet: more grip at the rear, and much more precision in the steering for the front. The Grasshopper II remains a 2 wheel drive buggy, but the tire set is a true benefit. The front suspension is also much softer than on my Hornet and sticks to the ground. It is even so soft that I'll have to harden it a little bit as the front drivetrain tends to get too low.

At the rear, the Hornet hydraulic suspension is much more efficient than the Grasshopper II springs that make it bounce a lot. Well, in fact this is to be tempered: as long as the third rear shock kept working, the buggy behavior was a little better than on the Hornet. But as it didn't last long (the screw and nuts played a Prison Break episode), the Grasshopper II soon recovered it natural behavior: to bounce on the first peeble. So now I have to study again how to fix it better.

So overall, the Grasshopper II does belong to its lineage. It is a very pleasant buggy to drive as long as you don't expect performances it can't give because it has never been made for that. It is robust, it can be driven hard and will definitely be a "serious basher".

Bonus: the promotional video of the Grasshopper II when it was released back in 1988 (© Tamiya). If you think you see a Madbull, then this video could be considered as premonitory...

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First publication: april 14, 2008 Last modified: august 05, 2009

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