KYOSHO OPTIMA MID HYBRID

Maiden Voyage

2009-04-24T18:45:00.000-07:00

Indeed, today was the day for the maiden voyage of this rebuilt Hybrid Optima Mid. But first the preparations to get to there.

Remember I said that the ESC needed rewiring for the receiver? I used a 1x3 .025 square pin terminal strip to connect the two units. Neatly finished off with some clear shrink tubing and now we have a simple rewired ESC control connector.

This is how it dressed out in the car; a bit of a service loop, cable draped over the battery holder, and a bit of double sticky tape on the backside of the connector.

Overall, a pretty tidy wiring solution if I do say so myself. Here you see an ancient NiCD 6-cell battery pack which a friend brought by a few days ago. To my surprise, all the cells warmed up fairly evenly and peaked just fine after two false starts.

Remember my complaining about the radio battery connection being glitchy? Well! Look what I found in an old cable bin in the cabinets! An extension cord from game system of some sort. Having ohm'd out the wires and determining I wasn't going to melt my battery pack, or zap the controller, I plugged the two ends of the cable to their respective sockets and it worked! This makes me a very happy camper.

I also said the car weighed in at below ROAR legal weight of 3-1/2 lbs in this Stock Class configuration... here it the proof [you'll have to take my word on the zeroing of the scale though]

After a cold run on the scale to check for serious flaws, I was confident enough to push some power through the car. Here you get the same first look at performance as I did. Thanks to my wonderful wife and her extra-ordinary skill in following fast moving objects with the camera.

I am indeed pleased with the performance. I'll do some more video analysis but I can swear that the front end was nearly off the ground, and if traction was improved, they would have been. I was well impressed with the cornering stability as the car actually pulled into the corners under power.

It has been a great adventure to bring this hidden treasure back to life. I am also glad to have documented the intricacies that make up this absolutely unique manifestation of Kyosho's finest machines. I hope you too have found a gem or two of wisdom from these pages.

Please feel free to add comments or question and if and when I see them, I will do my best to reply.

Peace; Out!

Final Assembly

2009-04-23T20:15:00.000-07:00

"The end is near!" ...so the morbid and the doomsayers say. But also those on a quest... being left with mixed emotions of gladness and sadness all at the same time.

The facts are clear; all the prep-work pays off in the assembly process. First we used medical fabric tape to close up the hole on the front differential case: Great stuff!

Next, push in the shafts holding the a-arms in place and tighten the set screws. Remember that the front shock was air free? Well, it seems pretty good for now.

Same for the rear suspension; add pins, and washer shims as required, and bolt on the shock and control arm plate. Note that the shock mount is not per the original Optima Mid design as it is now one large plate. Oh, I also made a wing in the meantime... you'll see more of it in a minute but I did install it once the plate was installed to the differential case.

A cursory check of the control arm lengths, front and rear, show them to be in a reasonable starting position. When we dial in the car we'll see what needs changing.

Next is the battery hold down. This is one of the stock Optima zip ties for the battery holder. One end is routed through the chassis and held just in front of the steering servo...

...The other end too is routed through the chassis and then the screw and post are inserted to hold the battery in place. The recess in the chassis keeps the battery from sliding forward into the front side brackets.

The orientation of the battery in such a fashion is great from a high-center CG point of view. It makes body roll much more consistent in high speed off-road cornering. A trick I learned from another custom Optima project.

The rear shocks were not quite as nice to me and really screamed "Rebuild Me!". So here you have a unique look at some rare shocks. These too came from the mystery 4WD kit. These feature a removable seal end, shoulder washers (2), and o-ring seals (2). In the top of the shock is the common bladder for pressure relief for the shaft volume. One feature I remember putting into this car was a beveled split washer below the piston. There is no free play between the shaft and piston.

Not having any shock oil, and not even knowing what weight I'm going to need, I opted for household oil for the time being. It felt pretty good for getting a few rides in. Notice that I moved the shocks bottom pivots back to the a-arms. If I do move them to the knuckle, I'll need to lengthen the shock bolts on top.

Then comes the true button up... adding the motor. I picked my green Rev Tech(?). I have an old motor plate that is meant to let air flow through the motor but not blow chunks into the gear cover. The o-ring closes all openings. I also picked a relatively small pinion because I suspect this is a pretty low wind motor, like 14 or 15 turn.

After letting the double sticky tape cure overnight on both the chassis and the ESC, the two came together for a very tight bond. This was pretty simple. Remember that I picked the location pretty carefully so it won't interfere with the motor as the pinion or spur gear gets larger. The motor wiring came out sweet and simple!

Here is a shot of the car with wing and wheels. The wing has some plastic wing mounts and some thick piano wire. The wing itself is aluminum with a single bend. This is a very solid solution. The tires have barely been run but I suppose that they will wear into slicks pretty quickly.

I still need to make a 7.2v pack and modify the ESC control connector. In short, this car is just about ready to roll. The end -IS- near :)

Assembly - day 2

2009-04-22T17:42:00.000-07:00

One of the challenges of 4WD systems is keeping the dirt out. Dirt tends to pack into belt cogs and grit shortens the life of your main bearings. Sacrificial plastic gears don't stand a chance. Well, fabricating custom drive train covers is simpler than one may think. As with the lower chain cover, the top chain cover is a simple plastic tube. Ever wanted to know what to do with used overhead projector "foils"? Here is the perfect fate for those otherwise useless spent plastic sheets. First things first; optimize! This is the front of the tube...

...and this is the back of the tube. Note they are different depths.

A overhead transparency foil, a straight edge, an X-Acto knife, and some tape is all that is needed to make a very effective dirt blocker. These are the number I used: The sheet is 8.5" wide... and on each end I scribed a small mark at the distances noted: this is the front case opening...

...and this is the rear case opening:

With the scribe lines in place, I now connect the two marks with the straight edge. This is important! ...scribe along the straight edge using the -backside- of the blade. This provides for a very nice scoreline without going through the plastic. I trimmed about 1/8" off one end to make the length correct. I also put a strip of tape on either end to keep it from splitting. Now trim away the extra plastic beyond the score lines and fold the remainder into a tube.

I will be the first to admit that I should have done this before the side plates and steering were added. The heat sink too got in the way a little bit but that is not to say that it cannot be done in this order. Obviously, I got it on there, and I did not do any disassembly.

The final step is to put 4 pieces of tape equally spaced along the length of the tube to hold it closed. Here is a closeup with what you should have ended up with:

...and in the back:

The overlap is on top with the opening toward the left side of the car.

I had a little time left over to look at the ESC. This unit is definitely larger than the previous Novak I had in this car. Making room for the motor, ESC, and battery has become a bit more tricky. I am looking forward to using tat torque feature, though. I mounted the switch on the controller with double sided thick tape. Usually, I don't use no stinkin' switch, but what the heck, live a little. And then I taped the wire to the back of the ESC to manage this switch wire loop.

When all is said and done, the ESC will be living in the approximate position shown:

It took a while to get the chain cover just right but I am confident that this will serve its purpose quite well. Other materials I can suggest include a 5-mil Mylar. Even stiff plastic sheeting will work. The trick is to be able to score the material without having it split. Here is where we stand so far with the assembly.

Looks like the suspension will be next!

Assembly Begins - day 1

2009-04-21T18:47:00.000-07:00

This happened faster than I thought. The chore was to enclose the lower drive chain. Goal; not to separate the chain. First things first... I put the two a-arm pins into the chassis. I had notched the rods so that the set screws, seen here, keep the pins from backing out. There are actually 3 set screw but the one at the top of the screen is only for making sure they are parallel. Originally, I had the back a-arms somewhat canted inward. I'm going for parallel now. The difference is using a different end plate. I have a carbon fiber end plate that has the two holes for the pins set further apart. Since I want good high speed tracking in a straight line, this will work best for the on-road setup.

I had a piece of clear plastic sheeting laying around which I cut to 20mm wide. I then took some sharp small hobby scissors and trimmed in the ends. These two pictures show well the conditions I was after.

The tab into the plastic on the front is only about 1/8" long. Being relatively stiff, there is no reason to worry about the tab getting caught by the chain.

Next, I put double sticky cellophane tape on the chassis where the plastic sheet will be adhered. Since the chain length was already correct, I just placed the front and rear case assemblies in the chassis so the chain would lay in the slot. Next, I simply started to lay down the plastic strip as it adhered to the double sticky tape. Had I thought ahead a bit further, I would have left the front brace on the rear gear housing assembly off. The front brace, the H-bracket, can be removed at any time if more finger space is required. Remember that at this point, the gear cases are just sitting there.

In case off-road dirt tracking is anticipated, one could consider a much more substantial covering of the additional grooves in the chassis. I consider this optional as only the chain needs to be protected form the elements that might find their way into the gearboxes.

After careful inspection of the chain cover, it is time to consider committing the gear cases tot he chassis. I spent some time selecting appropriate screws form the handy hardware box and found everything I needed.

Once the chain is set for tension, which in this case is fully retracted, a few pieces of packing tape seal off the last few crevices at the chain cover. You have to look pretty close to see this piece.

And a piece in the back about 10mm x 20mm:

It is amazing how effective this simple solution is. And even after 15 years, the previous tape came right off without a fuss. If the car will always be run in a clean environment, like carpet tracks, I'd say the chain cover is completely optional.

Now we are ready to put the steering back; add the side plates;...

...and have our first close look at the front bumper which protects that mono-shock.

Notice that the upper control arm keeper has a hole drilled in it right next to the metal brace. The looped .090" diameter piano wire has spring tension holding it to the very front metal bracket. Overall, this is a very stiff system although I did back this up with fabric tape so I wouldn't loose a piece on the track somewhere due to an "incident".

So this is where I finished yesterday. I will post the next steps soon.

Nemesis!

2009-04-20T23:00:00.000-07:00

Seems everyone has at least one task, feature, or design that just fights you every step of the way... mine is wing stays!

After going through the trouble of making new wing stays, I just couldn't get the screws short enough to keep them from interfering with the wing wire. I got there eventually, but gheeze... what does it take!

This is what I ended up with: SAE 6-32 hardware and the aluminum posts that have a shoulder which have a nice tight fit in the carbon fiber holes.

..and the set screws will keep things nice and tight... right?

Now to figure out what I want to do for a wing. The one I have is pretty beat up. I might just fold one up from an alloy sheet. I like those best.

I got a lot more done today as I began the re-assembly. It is a little late for me to blog this effort tonight so please stay tuned. Here is a sneak peak:

The gear cases are installed and the bottom chain guide is now sealed. I'll take you through this tomorrow.

Parts Prep - day 5

2009-04-19T17:02:00.000-07:00

Having concentrated on the main chassis long enough... and not having any epoxy on hand... I decided to do some work on the business end of the car: the suspension.
These things look so simple when they are in one piece. Funny just how much makes up the driving end of the typical RC car. Here is a shot before disassembling the suspension...

...and after

Much of the magic in this car is in the front suspension. The carbon fiber mono-shock adapter plates just begged to be mounted to the Maxxum long a-arms. The wing-mounts on the back are for hard stops at full sag.

And the steering knuckles were reversed [L<->R] so the steering arm allows for maximum steering angle, or in other words, smallest turning radius.

The a-arms and the pivot are completely stock. No carving or tapping. They are completely independent with regard lo left and right. Not so for the steering knuckles. These are ground for maximum clearance both at the universal joints and at the a-arm. This is so that the full motion of the a-arms can be maximized for the mono-shock arrangement. For the most part, it is a pretty simple modification on the surface, but as you have already seen, the front gear case had to be modified for the shock, and you will see how the gear case bottom plate is reinforced for the rigors of racing in a few more days.

By the way, I failed to mention my ball bearing lube of choice: I've been using ProGold Lubricant's ProLink chain lubricant for bicycle chains. In the cycling world, this is the "go back to" lube of choice when the new fad fades. I've found this lube to be quite effective.

Back to the car. On the rear suspension, there is often quite a bit of play between the a-arm and the knuckle. This is where a handful of 3mm washers can be quite useful to take up some extra slop in the system.

In this case too, the rear a-arms are fully stock, unmolested Turbo Optima a-arms. I did decide to move the shock balls to the knuckle for better cornering. In general, I will be lowering the car's stance to make it more stable in high traction cornering. If I'm not mistaken, I think I have a short-shock carbon fiber shock mount that would allow for the Kyosho Gold short shocks to be installed in the back. If I'm not careful, I'll be searching for an on-road body soon! For now, I have the custom carbon fiber shock mount and control rod stay. There are plenty of options for dialing in the wheel's attitude.

As for those shocks in the image, these too were from the mystery 4WD. Notice that both ends can be removed. I've put Kyosho's Gold shock plastics and springs on these shocks as well as new red rod ends from the original Optima's red shocks. These shocks still need to be rebuilt once I figure out what to use for shock oil. Here is the same shock on the front suspension...

Funny thing is, the front shock is still air-free/leak-free. I have a feeling the oil's viscosity is just a little too heavy for on-road use. I'll probably save the shock work for last.

If you look carefully at the image, you can see the grinding done on the steering knuckles.

I went through the hunt for good rod ends. I seem to have plenty of usable rod ends in the bone pile. I also found the left & right handed turn buckles for the back.

One of the wheel bearing needed replacing and the universals were still in pretty good shape. That is one item I haven't seen show up on eBay... dog-bones and universal shafts for Optima. Does anyone know if later Kyosho models use compatible universal joints that are readily available? I may just have to learn how to re-join the ends of the shafts I have in the bone-box.

Next I need to commence with completing the chassis. We are not far from the assembly process. Stay tuned!

Parts Prep - day 4

2009-04-18T18:28:00.000-07:00

Today was a productive day. Having decided on the drivetrain made the next step pretty simply; overhaul the gearbox and differentials. I began with the front. Much to my surprise, I fully neglected putting any type of grease in the front diff. This is not like me so there must have been a reason I did this. This front diff had very smooth action and was still perfectly good for continued service. I decided that cleaning the bearings and changing out the casing for new was a worthwhile effort. I do remember all the deflashing that the bevel gears required in the past. The effort of filing the gear teeth clean makes the diff performance 10-fold improved. Notice that I use shield washers on the outside for the bearing to help keep the bearings clean. The bearings barely had a film on them.

During re-assembly, I used my favorite hobby grease: Parma Silicone Lube #7900. This lube applies thick but tends to ooze into all the crevices over time. This lube is safe for plastics and is tenacious about minimizing friction. In the long run, it will ooze out of wherever you put it so you want to use it sparingly. One bottle will likely last a pervasive hobbyist a lifetime.

Here is a shot of the assembled front differential. I reversed the drivers so the wear surface is virtually new. I try to take out all the sideplay when tightening the drivers on. I also use a hard hex wrench and make sure these are tightened very well. If you've been collecting Optimas for a while, you will notice that the setscrews used here are quite rare in your parts boxes.

Next, apart comes the custom dual chaindrive ball-diff. The unit was a bit raspy and definitely a bit dusty. If you've never worked on one of these, this section will be one for you to pay much attention to if you ever plan to install one.

I could easily have put a normal bevel gear style rear diff in this Mid. The shear beauty and performance of these units makes this little adventure well worthwhile. These can be set up as slippers [not recommended on 4WD] or simply dial in the drive you want to push onto the outside wheel. I set mine up to where the plates would slip only in case of a hard shock. I replaced the plates as the ones I removed were pretty rough. The bevel washers were still in good shape, and the small thrust bearing was in pretty good condition. The screw still had some thread lock on it, and the foam washer also was in good shape. Overall, this was simpler than I had anticipated. Please note the error in the photo... you cannot use a shim washer on the left side bearing! Doing so would keep the driver from engaging properly with the disk.

This is where the two shim washers should go in order to keep the bearing clean. Also notice the orientation of the bevel washers: <><><> ...followed by 2 special washers for the thrust bearing. The foam plug has a hole in it to make adjustments without removing it.

Here again, the Parma grease did its usual perfect works by holding the 8 balls in the thrust bearing. This was just what Doc ordered to slide this sub-assembly into the driver.

Always check the function of your ball diff after your first run when you've rebuilt the unit. These tend to require a little break-in period. One other word of warning about this ball diff... the part were the balls are installed must be on the drive side! Reversing this will diminish performance.

So here you have them, a virtually new set of differential. Sweet!

Next comes a perplexity that comes to light only after you try something new and have never really had to, or had the chance to correct the little mechanical nuances. In this case, the slack side of the drive chain is wearing the boss for the case screw. If I recall correctly, I had one track-side repair to replace the power side drive chain. I can imagine that slapping the chain against the case had something to do with that. The wear area is the "I I" on the right gear case.

This was my determined correction to the shortcoming. I ground away the plastic to make room for a hard rod end ball. It is not meant to spin, but it is there to make sure that the chain can glide past it and maintain its dimensional shape. A screw is used to keep the ball in place through assembly when you push the right screw through exchanging the ball's holding shaft.

When all is said and done, nothing has been changed except the expected lifetime of both chain and case. This setup has a near perfect fit for this chain-pitch. Backlash is quite minimal. Do notice that one of the case mods is removing one of the back screw bosses.

With a 7-18, or 2.57:1 ratio, this is pretty much the same as stock 14-37, or 2.64:1 ratio.

Here is a quick video of how efficient this drivetrain really is.

Now for a second shortcoming of my original build. Obviously, I never checked the spacing of the two pinions as compared to the differential itself. Turned out I needed to remove almost .050" from the idler pinion to have the two match up properly. I seem to have had the chain biased quite heavily to the right in operation. This might have been the second reason for the broken power drive chain. Today I put the idler on the lathe and matched it all up.

I have no excuse for this oversight other than sloppy work. I am glad I had the opportunity to fix this as this car will see a whole lot more power run through it than it was originally designed for. Remember, this was a car dedicated to ROAR 4WD Stock Class racing. I fully anticipate putting my Rev Tech Red on this car. This car has never flown as fast as this motor can take it.

Here is another piece of the how-to puzzle. This mystery car that sacrificed the needed technology to make this modification possible also had a simple and clean solution for the spur gear... a flange that the gear simply screwed onto. The flange has 2 setscrews the same size as your everyday pinions. The reason this flange is key is that the drive shaft is 4mm vs the 5mm of the Mid. Even the bearings have a spacer in it to make them 4x10's. I'm also happy with the fact that this is a 48-pitch gear... since I have a nice collections of 48-pitch pinions.

The next image is to preserve the knowledge of the sequence of all the spacers and shims to allow for minimal side play. I left out one of the shims, the second one to the left from the idler. Even though the idler is free-floating, it will rotate at the same speed as the drive pinion. If you look carefully at the 7T idler, you will see I had to cut into the setscrew holes.

Again, be sure the diff is installed correctly!

The next step is pretty straight forward... add bolts, motor plate and battery holder [H-bracket]. One bolt through the wing mount serves to replace the hacked case screw; and the new ball in the case is in place. Again, push the screw out holding the ball with the screw that goes through the case. That way you know it hasn't fallen free.

I played with the chain a bit to make sure it rolled freely over the 7T cog. The chain did have a rough spot where it was joined. Working with it a bit made it behave as I would expect it to.

Here is a shot of the diff cases on the chassis. Notice I also marked the connector signals for the ESC on the receiver.

I think I am pretty close to buttoning up the chassis and drivetrain. I have a little epoxy work to do on the chassis first. I also need to make new chainguards from Mylar sheets. Do you think I can put all the pieces together without breaking the chain and threading it through the chassis? We'll see!

Parts Prep - day 3

2009-04-17T23:57:00.000-07:00

The last of the metal parts are now dusty-gray as I completed the bead-blasting efforts. This Mid has a motor plate heatsink salvaged from an old circuit board. It doubles as a body mount with one of the standard Mid plastic parts. I blasted the gold anodize off and reground the interface to the motor plate for good heat transfer. Pretty classy and indeed a functional piece of bling, if I do say so myself:

The front and rear a-arm plates were also blasted to complete the set. ...And you're saying "...what about the motor plate?". I think that the motor plate is best left as-is since the motor and mounting screws need to slide back and forth, which requires a smooth surface. The heatsink interface too needs to be smooth. Therefore, these last few parts should complete the sparkly icy gray aesthetics of this buggy:

And I've decided on the front diff gears; I'm using the 18T/Nil combo when I rebuild it. Reason being, you really don't want to underdrive the front end of a 4WD buggy. This would be worse than trying to drive a 2WD car, which, I for one, can't drive worth beans. Perhaps someone will correct me on this, in which case I have plenty of new spare 19T gears that I will include in the kit. Either way, you have to disassemble the front end to make the swap. One of the reasons for this decision is the rear Diff. Take a close look and wonder at its uniqueness:

Indeed, that is a dual chaindrive rear ball differential... quite custom. The teeth and belt gears were machined off of the Optionhouse ball diff and stock chain gears were machined to slip right onto the housing. A little superglue and wallah, dual chaindrive ball diff! Yes, I like having a ball diff on the rear of a high speed road buggy. It guarantees having drive on the outside wheel in case the inside wheel gets a little light. Not so for the front end. I like to leave the front wheels very independent with a smooth free running set of bevel gears. Just to be clear, I've decided to bring this car back to its glory as a dual chaindrive Optima Mid Hybrid. This will keep this car absolutely unique to every degree in the Kyosho line.

I have also been a bit worried about what to do about a ESC. At one time, I loaned the ESC, a Novak all custom wired for this buggy, to an old race partner. Somehow I ended up with 3 other speed controllers in my box... an old Futaba with reverse, no stickers; a Tekin that looked pretty much toasted with wires missing and such; and a Tekin TSC 411P with Torque Control. It must be an early model as it didn't have the fuse built in. It is wired with compatible connectors and the control wires can easily be modified. Luckily I could easily discern the Novak receiver's pinout... as this is hardwired with a flying lead. This is the unit that I will use:

I charged a 7-cell battery pack and loaded a set of AA's into the old, beat up Magnum Senior radio. It took a little convincing, but the radio finally decided to behave. I think I need to make a remote battery cable for it if I don't want it glitching out on me. The radio has more buttons and knobs then I ever wanted. I adapted the ESC control cable to the receiver with a set of pins; plugged in the battery; and turned on the radio and the ESC switch... and crossed my fingers no smoke escaped from the electronics. I waited to plug in a motor so I commenced with dialing in the steering. I was anxious to see how well the new linkage would work. With much fiddling and fondling the radio knobs, I finally figured out what did what. Here is a shot of the setup:

I was really happy that the ESC powered the receiver properly and supplied power to the servo. Here is the steering linkage in action:

Next, the motor test. I wasn't sure what the blinking radio power indicator meant... this radio is a 3-channel radio for gas systems which has a warmup switch. The motor was acting a little weird when I first plugged it in. Then I figured out what the proper setting should be... the light should be on solid by turning warmup off... DUH!

It didn't take much to dial in the ESC and the radio for the motor. The brake trim is a bit touchy but all that will be dialed in on the road. I ran it on a modified "green" motor; an old Rev Tech maybe. Not wanting to throw a winding or stress the brake FET, I decided to just chill it and be satisfied with the fact that I have a functional setup for when the car is complete. I'll post the radio here just to archive the knob's positions for later:

One of the things I haven't been able to show you is the battery position. I learned a long time ago on another Optima that a lengthwise battery makes the car very stable in corners... stick to the ground, so to speak. This car can hold a 6-cell or 7-cell pack. The 6-cell is a normal stick, while a 7-cell has 3 cells side by side in the middle. I haven't seen this configuration in a commercial pack, but it is quite easy to make. Once I get around to running the car you will see what I mean, but for the meantime, this is the motor end of the battery holder. That's right, the battery lays right on top of the chain groove in the chassis:

Parts Prep - day 2

2009-04-16T19:59:00.000-07:00

To follow up on yesterday, the front side-plates were bead-blasted to match the base. A little grinding smoothed out some of the unused features. Gotta love the way a bit of blasting erases so many years of abuse:

The real task for today was refurbishing the chassis. A chunk of fiberglass that started life as a peg-board circuit test fixture salvaged in a warehouse clearance give-away. A small router table, a Dremel tool, and some careful planning and fixturing brought this chassis into shape. Holes are tapped directly in the fiberglass. Some of the holes were not perfectly made, and some trackside chain repairs have allowed some desperate alterations to compromise the holes. Today, all the M2,5 holes were deepened and retapped. All were salvaged and the new screw of choice is a Schroff offering for their electronics racks. Their length and large head diameter is uniquely appropriate for this application. Here is a closeup of the screw:

Having limited access to real shop tools does have its advantages. The pilot holes and the tapping were done with much greater precision that the 1st time around. The other mod required, as eluded to yesterday, was to counterbore the holes for the steering linkage - pivots. This was done with a drill press and a 7,5mm mill bit. It was a bit touchy trying to keep the bit centered over the hole. But if you recall, the 1/4" hex shaft required a 3mm deep counterbore. As you can see, this was accomplished beautifully:

And a 2nd plus about this revised features; all the screws are the same:

...except these, which I had to nip the tops off of:

When I assembled the plastics, the tips of the front sideplate screws now protrude past the plastic. A quick nip of the front gearcase took care of that:

Here is a shot of the steering linkage installed:

...and the sideplates:

...and with the diff case:

...and this is a 1,000 words all put into technicolor!

A final word about this chassis: all these tapped holes are M2,5 with plenty of material for M3 tapping. Some custom undercut M3 screws [captured hardware] could be used. That simply means that there is an M3 hole tapped in the metal plate slots and drive the screws in [captured]. Once loosely fastened to the chassis, the slots would work as before to adjust the chain.

Of course, this level of progress only begs the other questions that must be answered... Which drivetrain?

I've wondered if I can belt-drive this setup. I have all fresh [new] parts to make this a sweet belt drive buggy: new ball diffs; hardened pinion; new cases; new spur gears and full bearing set... but alas, this chassis is a long chassis that requires a different belt length. And I don't know what that length would be. It also turns out that Kyosho took a standard belt type... the XL series, and ordered a special narrow version of it. So this makes industrial suppliers less likely to want to talk to us hobbyists. So, since this buggy has always been a chaindrive buggy... and chaindrives are ~very~ efficient [and rebuildable!], we will stick with chaindrive.

The front differential is in perfect shape. The bearing spin freely, dirt and dust is absolutely minimal and the bevel gears spin quite freely and smoothly. The washers at the bearings are a great way to avoid dirt in the bearings. It could go back in as is and it would be perfect... but then again, a rebuild demands inspection, and since I have dozens of unused chain gears, I could dedicate a new set of plastics to the rebuild. Even the dogbone drivers are in really good shape signifying the low hours on this car. This car has been run using stock class motors for the most part. Now my dilemma... 18T/19T or 18T/Blank?

This is only the beginning of difficult choices. I have every intention to make the rebuild on-road compatible. This means that I don't want the front wheels over/underdriven. This is a good reminder of this unique option provided on the original Optima. At one point, I obtained a belt drive gear with this function but it never went anywhere. The real difficult choice is still looming in the back of my mind... dual chain drive ball diff or conventional diff and conventional gearing for the gearbox. Stay tuned!

Parts Prep - day 1

2009-04-15T22:08:00.000-07:00

Now that the car is a basket case, it is a good time to start working on the individual parts and functions. Last night was the recovery of the front bottom plate. Yep, that is the original Optima plate, this one from the parts bins. I prefer this part because the slotted holes were not countersunk. This will making chain tension adjustments much easier. Here is the "before" shot of the front end:

Notice the steering linkage resembles that of the Ultima with the floating beam connected to the tie rods. The beam is carbon fiber shimmed with washers and attached with kingpin bolt. The rest of the linkage is stock original Optima complete with the posts that are attached with the M2,5 screws. When I disassembled the car, the bolt on the saver side [left] broke and was stuck in the aluminum tube. Sorry to say I didn't have any spares so a little fabrication was necessary. I decided that I could change the design a bit as this car has a solid chassis rather than the rails. I will be counterboring the fixed steering pins into the chassis. The aluminum strap normally on the Optima is not needed. Here is a shot of the steering linkage with the new pins and special washer:

The new pivots are made of brass and the small brass hex pieces are washers for the flathead screws. Nice thing is, the hex is 1/4"; the clearance is appropriate between the two parts; and the fit is just about perfect. A dab of bicycle bearing grease and all is good. Notice the large washers... these are used to preload the servo-saver spring. There is a servo-saver on the servo itself so this is just gravy. Here is a closeup of the pivots assembled:

Now to add the tie rod assembly:

And finally a shot of the assembled linkage: [tie-plate present only for stabilizing the assembly]

That pretty much does it for the steering linkage. Nice smooth action, solid and extreme range. So far so good.

The tape that was used to seal the front case was quite stubborn. It took some serious convincing to remove, but the effort was well worth it. You will notice that the cases were modified to account for the mono-shock. This leaves a hole that needs covering. As this build progresses, i will see if there is a better way to deal with this unwanted feature. Here are a few shots of the cases and the salvaged bottom plate:

Notice the difference in the setscrew sizes for the a-arm shafts. It is good to know that a case can be salvaged buy tapping out the hole for the next size setscrew. I may go back and make them match.

The bottom plate was pretty rough. It has seen quite a few high flying jumps but overall, it was in pretty good shape. Kyosho had put forth several thicknesses of this part. This one is 1,5mm thick. The previous one was 2,0mm thick. I also took the hammer to lowered portion of the plate where the chain-guide use to be. This can be flat in this application. This also makes the underside flat. If you look carefully at the image, you will also see where I files the transition of the chain from the differential stamping to the flat part. That should help save a chain or two. Here are some pics of the bottom plate after bead-blasting. Cleaned up pretty nicely, don't you think?

Looks like I will be following up on the rest of the front assembly in the next few day. This means that chassis mods are coming soon. Stay tuned.

Awakening!

2009-04-14T19:59:00.000-07:00

Many moons have drifted across the horizon since the day this subject has seen the light of day. Had it not been for the ever increasing need for horizontal space, many more moons may have simply drifted by until one day this blast from the past would simply have found its way onto a table at the local flea market or neighborhood garage sale.

"What the heck are you talking about!" I hear crowing in the distance...

In a past life, many days were spent with a hobby so gripping that hardly anything else was important. It started out innocently enough... a small investment in a toy remote controlled car simply to pass the time. A pretty natural hobby choice for a technical tinkerer. Well, if I had only known all that followed for nearly a decade.

The RC car I choose was a KYOSHO JAVELIN. A 4WD 1/10th scale off-road racer. Little did I know that this model would one day become a very competitive race car.

Of course, the first thing one finds out about RC cars is that "upgrades" are available... which brings you into the hobby store... where you find out the "hobby" is also a competitive sport! Sport! ...you say? "Ha... another hooked" is what was going through the mind of the owner of RC Modeler NW, one of the ma and pop shops in Beaverton Oregon. Yep... that's how it started.

The purpose of this blog is not to reminisce about the good 'ol days. No, the purpose of this blog is to chronicle the rebuilding of one of the offspring spawned from the bags and boxes of parts that originated from what I affectionately refer to as "the pegboard catalog"... meaning the wall of replacement and upgrade parts at the hobby stores.

3rd party parts suppliers were not going to be outdone either. For every good race car, there are others that feel they can do better. Companies like Thorp, MRC, A&L Manufacturing, and many others help contribute to the fever of faster, further, and higher. Some great advancements made the sport more competitive and ever more addictive.

We fast forward several years to when Kyosho pretty much ended their rear engine Optima series. Kyosho's next offering was a mid-ship motor model named aptly, the Optima Mid. Some vast improvements were made in the gear-train as well as standardizing many of the upgrade parts that Kyosho offered under their OptionHouse brand. The real wisdom in Kyosho's line is the backwards compatibility of so many parts and options.

Having invested heavily in the 1st generation Optima, and being intrigued with the new generation, I began a project joining the best of both models. The new mid-engine design was pretty much a no-brainer. Longer wheelbase models were pretty much the rage as well... and on the track, one model was just a smoking machine that glued itself to the track and flew! I'm referring to the Yokomo 4wd. The unique feature of this car was an independent mono-shock front end.

Another influence in the new build was a little known, short lived 1/10th scale model that I cannot even recall the name of. The chassis was made form 2 carbon fiber side plates, orange a-arms, and the very same chain-drive as in the original Optima. What was unique about this car is the fact that not only the fwd was chain-drive, but the final pinion was also a chain-drive, eliminating a counter gear in the setup. Another unique feature of this drive train was the simple spur gear adapter plate. This made it simple to bolt on just about any spur gear.

Okay, I am armed with all I want in a 1/10th scale 4WD off-road racer. My skills were honed to be dangerous with a Dremel tool... specifically the cutoff wheels. I learned to fabricate plates from a single carbon fiber sheet I purchased off the pegboard catalog. That sheet was used for years of fabrication. The bigger challenge was the chassis. Having learned let level of punishment these cars have to endure, this was not an easy choice. Cars have been known to fly 6-7ft in the air and land 20 feet later. These machines are not always to graceful about landing, either. That is why most come with bumpers [like that does any good!].

Oh yea... the purpose of this blog is to recap the building of this unique Optima Hybrid Mid RC car. I will chronicle the rebuilding of this car in order to capture the nuances of its design. I will likely rebuild it differently that the original intent simply because today's motors are much more powerful and run-times are 3x what they use to be. I do not envision this creation finding itself back on the racetrack. Not that it cannot do this, but more that there is no reason to. This will be up to the new owner. Yes, the new owner! I am rebuilding this car with the intent to sell it. This blog will capture the subtleties in care and maintenance of this car.

Please follow along as this journey commences. This is the status today: