Madcap built with Astute parts.

[Saito2]

Confession time. I have a love/hate, no...love/disappointment relationship with the Astute. I always found it to a beautiful buggy with great capability let down by some odd and inexperienced design ideas mixed with typical Tamiya materials of the day.

To set the stage, I was hungry for a new competition level 2wd car from Tamiya back then. While the 4wd buggies were constantly developed, Tamiya kinda left 2wd to entry level (Grasshopper/Hornet/etc.) and mid tier (Falcon/Sonic Fighter) offerings. Their jumps in "competition oriented"  2wds from the Super Champ to the Frog basically stopped at the Fox. The Fox, never a hardcore contender against the RC10's dominance at the track, was quite long in the tooth by '89 when a promising new 2wd buggy came out, the Astute. Glancing at the preview shots, the Astute, part of an all-new breed of off-roaders from Tamiya that year, looked like a viable contender. When I finally saw one at the hobby shop, the peculiarities like the adjustable rear hubs and tiny bushings residing at just about every pivot point stood out. Feelings were mixed. I liked Tamiya's typically unique approach but I was also concerned about possible needless complexity (leading to potential fragility) having just been through the original Avante fiasco. As it turned out, those feelings weren't too far off base unfortunately. While I appreciate Tamiya's refusal to be cookie-cutter, seeing breakages at the track made me think oh why couldn't they have keep things simple and emulated the RC10?

As it turned out, they had, just in the Astute's little brother, the Madcap. Despite being mostly plastic, lacking the Astute's cool, in vogue, monoplate chassis, the Madcap was the basic 2wd car with potential I had hoped for. Bearings, oil shocks, and a metal motor mount were all it took to get this lightweight buggy keeping pace with an RC10. It might not have been quite as tough as Associated's aluminum tub wonder but it wasn't exactly as fragile as the Astute either. The fact that many pro Astute drivers "downgraded" their rides with simpler, lighter Madcap parts wasn't lost either. I waiting for an Astute loyalist to leap to the buggy's defense, claiming its rock-solid reliability. Maybe it was for them and that's good but it wasn't what we experienced in our area. As always, your mileage may vary. 

Here's my old Madcap racer BITD. It was tired by then, but still holding together.

Here it is nearing its restoration completion.

 

When the Super Astute was re-released back in 2018, I was keen to get one. Tamiya had made changes, simplifying the buggy. It offered a unique look at a platform that Tamiya actually race developed. It still retained some annoyances though, like the bronze bushed pivot points and the criminal use of press nuts. While mine stayed on my shelf over the years, Tamiya bringing it back at a much cheaper price juxtaposed against the much higher priced RC10 variants being shotgunned out this year stirred me into considering giving it another go around. The buggy just looks so beautiful.

A combination of future financial struggles to come and my stubbornness in preferring the simpler Madcap (along with encouragement from those here ) plus a surplus of old Madcap parts pushed me to forgo another Super Astute in favor of one pieced together, mostly from used Madcap parts.

This is as close as it gets to a build thread. It will be slow as parts trickle in and this topic sinks and bobs back up in the forum. I only know old stuff and how to put that stuff together (and most importantly, why I choose the parts I do). Its more a look back at the parts that worked the best and not a look forward at developing the buggy further. For me, there are race-bred tools today that do the job with such precision, that I'm happy living in the past, working mostly with what was around back then. Be back soon, same dirt time, same dirt channel.

[bavee]

Thanks for the write-up! Amazing look into the past.

[matisse]

Madcap has always been my favourite of the Tamiya 2wd buggies, something about the styling is just right.

looking forward to this. 

[Sgt.Speirs]

@Saito2: Great introduction!

Although the Madcap was part of the Astute familiy, it was not that common in Germany IMO. Here are also very few for sale on auction platforms compared to the UK.

I‘m looking forward to the thread😊

[Saito2]

Thanks guys!

Here's what we're starting with. You'll have to excuse the non-professional mess in my evil laboratory of green tea and shoegaze music. An old dish towel from my wife will be standing in for a slick cutting mat. Just off camera is a Frog and Big Boss in pieces. Its a mess but I know where everything is. All the parts visually look okay despite their advanced age. I went through my usual process of heating them up in water and then slowly allowing them to cool to "anneal" the plastics and relieve any internal stresses. Does it do anything? Maybe. I like to think so but then again, I'm vegetarian so can you really trust my mindset?

Of course I have a back-up for just about every piece pictured:

I got these parts for about $20 a long time ago for my runner Madcap and only used one, lol. The Super Astute FRP parts pictured also cost $20 from a kit breaker back in 2018. It was cheap and I figured I'd use them on a project someday. Well someday is here finally.

[naturbo2000]

Following! @Kol__ will be along shortly.

There's a lot of love for Madcaps and Astuted Madcaps on this forum. You can find my Super Madtute build thread and Kol's in the builds section of the forum. Also look out for @kontemax's excellent breakdown of the differences between Madcaps, Astutes and Super Astutes to help find the best balance.

My best advice is to look at Pargu's or Xtra Speed's front bulkhead. Probably one of the most important upgrades for me.

 

[BuggyDad]

Following with interest. 

May I ask why you've gone for the transverse Madcap battery position rather than the Super Astute in line position? It does give me the idea that maybe I could design a transverse shorty mount to bring weight forward a little. 

[JimBear]

"... my evil laboratory of green tea and shoegaze music."

@Saito2 - oh yes,  I'll come along for the ride!

[Saito2]

9 hours ago, BuggyDad said:

May I ask why you've gone for the transverse Madcap battery position rather than the Super Astute in line position?

The transverse battery cups were leftovers from my earlier Super Astute build so basically its because I'm cheap and this is a budget build trying to undercut the price of a new Super Astute, lol. In all honesty, I may spring for some re-re SA G-parts which have the in line battery mounts along with the front brace I'm curious to evaluate.

Much of what I've found over the years parallels the findings of Kontemax, though he goes into deeper depth. Great write-ups.

So here we have the rear arm mounts. As others have noticed, they are the same parts found on the Stadium Blitzer C-parts tree, which is where these are from. I figured 10 year old plastic might be better than 30 year old plastic. The C trees look very similar between the two models but Tamiya did modify the mold for the rear hubs (no longer on the tress pictured) when they re-used the tree for the Stadium Blitzer. In a pinch, I believe the rear hubs can be made to work for the Madcap with a little parts juggling but that won't be an issue here as I have original Madcap rear hubs to use.

The rear arm mounts for the Madcap are both meatier, thus stronger, and lighter than the Super Astute version with its bushings installed. The SA did add the advantage of using a crossbar across the front pins to increase durability over the original Astute. Obviously as others have seen, the 3rd outer hole won't be used on the SA's FRP chassis deck.

One can only guess at Tamiya's theory in using tiny bronze bushings at all the pivot points. My guess was to eliminate slop and offer the bushings as sacrificial wear items over the plastic parts. Tamiya were/are well known for what we call "Tamiya-slop" in the joints that's there from the first day. I'm sure maintaining hole tolerances is tricky with injection molding and subsequent material cooling rates. Tamiya seems to err on the side of "loose" traditionally to allow ease of assembly vs an old RC10 that might require careful drilling/filing to achieve a smooth pivot action (albeit with potentially less slop if done correctly by the assembler.). While more slop may negate some of the more fine adjustments made to the suspension, it does make for a less "edgy" vehicle when driving.

...and here we are installed. The front mount hole was tapped for an machine screw, thus allowing for an added nut. The rears are just tapping screws (heated before insertion to reduce installation fracture possibilities). There isn't clearance above them for a nut as the outdrive will reside there at a future time.

[Kol__]

Great start to the thread bud! Looks like she's gone be a mixed up ol' classic. Fully aware if your vintage bitsa build ethos on this one, but a word of warning with the Madcap rear arm mounts - they don't last on the Asute chassis, both of mine broke within a couple of runs. My rear end is now Super Astute with the brace bar and Xtra Speed alloy arm mounts. Seems tough as old boots now, so worth considering as and when the mounts break👍

Looking forward to seeing how this one develops😎😃

[BuggyDad]

9 hours ago, Kol__ said:

Great start to the thread bud! Looks like she's gone be a mixed up ol' classic. Fully aware if your vintage bitsa build ethos on this one, but a word of warning with the Madcap rear arm mounts - they don't last on the Asute chassis, both of mine broke within a couple of runs. My rear end is now Super Astute with the brace bar and Xtra Speed alloy arm mounts. Seems tough as old boots now, so worth considering as and when the mounts break👍

Looking forward to seeing how this one develops😎😃

Maybe if they're new plastic off the Blitzer tree they might fare a little better? Although of course, they'll still be a weak point. One thing I will look at pretty soon is to make another brace bar for behind the arms, to use with 3mm longer suspension pins (conveniently I think the M05 58mm pair should do the job - I use them on Blitzers too where I've done the same mod). It'll have to lift over the rear bumper screw bosses so depends on space back there, and it's conceivable I may have to modify/redesign or even lose my rear bumper, but at least in this case both braces will run outside the gearbox. I wasn't going to use the plastic mounts but now I think about it, if they're well braced like this, there's a chance a pair of Blitzer ones would then suffice and the mod render aluminum mounts surplus to requirements - I haven't yet broken a Blitzer or DT gearbox I've modded in this way (and I've broken at least three assembled stock).

[Saito2]

46 minutes ago, Kol__ said:

Xtra Speed alloy arm mounts

This is one of the benefits of the SA coming back, hop-up goodies like the Xrta Speed parts begin to circulate.

 

Well that's an exciting picture . Here we have a Madcap front bulkhead, again devoid of pivot bushings and possibly a bit more braced than the Astute one with some more molded in gussets. When Tamiya entered the world of monoplate composite deck chassis for 2wd buggies, they took the simple way out or rather the easier to manufacture way out by cutting the Astute's from a flat plate. Unlike buggies like the RC10, that had the front kick-up "molded" into the chassis itself, Tamiya added the kick-up via an molded plastic front bulkhead. It didn't really work for the rigors of competition. Its curious to contemplate whether Tamiya designers were aware of this weak point as the the Madcap, coming only and few models later and obviously co-developed alongside the Astute, came with a bulkhead brace (pictured ahead of the bulkhead in the above shot). Perhaps the brace was in the cards all along, simply to tie the mostly plastic Madcap's front end together. Either way, if one is to run there Astute briskly, a bulkhead brace is recommended. Tamiya themselves saw fit to add a specific one to the later Super Astute

So now I reach a decision point. I have the Madcap brace. It runs out closer to the front edge of the bulkhead and then back behind the shock tower mount. Without the Madcap tub, some risers or supports will have to be fashioned to attach it to existing hole in the FRP  chassis plate. The positives are that it supports a farther span of the overall bulkhead and cuts down on leverage forces. It also ties solely to the stronger FRP deck at the rear.  The negative is that since I'm using the SA FRP shock towers, the Madcap brace does not support that front tower as well as the original MC plastic front tower.

The other option is to use the G4 part off the Super Astute sprue (which will also yield me the longitudinal battery mounts) This brace ties to the front tower (adding support to the tower mount molded into the bulkhead) and shares screws with the two rearmost bulkhead mount holes. Less span length but greater tower support. I have a feeling the body I decide to run will determine this decision as I'm not sure the Astute shell will fit properly over the Madcap brace. Plan C(?) at this point, depending on my drive to save money, I might be to fashion my own brace.

Anywho, next on the Saito Hajime super show, we play the waiting game. Things are stalled until Tony's Tamiya Parts sends a small bundle over the pond this way and I get a special little package from the Bay of E. Hopefully I'll get to dive into Tamiya's rather interesting take on ball diffs of the period. Life's too short to be boring and just do everything like the other guys I've found as I've gotten older. In the immotal words of Porky J. Pig, that's all folks! (for now).

 

[BuggyDad]

6 hours ago, Saito2 said:

The other option is to use the G4 part off the Super Astute sprue (which will also yield me the longitudinal battery mounts) This brace ties to the front tower (adding support to the tower mount molded into the bulkhead) and shares screws with the two rearmost bulkhead mount holes. Less span length but greater tower support. I have a feeling the body I decide to run will determine this decision as I'm not sure the Astute shell will fit properly over the Madcap brace. Plan C(?) at this point, depending on my drive to save money, I might be to fashion my own brace.

Interested to see where you go with this. My sense is that the position of the Madcap brace, if braced back to structure like a tub, would be stronger than G4 down to a single deck chassis front. But, if you're using a single deck chassis, it would be better to brace down to the deck than horizontally back to the top of vertical standoffs.

That is, unless you then brace from those standoff tops to something further back. I don't think it'd be easy to do that passing the servo horn, so one question is do you go above it? And do you want a stiff double deck chassis anyway? It might change the driving character too much.

Bringing in 3d printing type mods I have a feeling there's a decent answer in there to designing a brace that's fixed more like G4, but might use sheet GRP/CF as its main spine, and is a bit taller, might even go over the steering bridge.

[BuggyDad]

9 hours ago, Saito2 said:

When Tamiya entered the world of monoplate composite deck chassis for 2wd buggies, they took the simple way out or rather the easier to manufacture way out by cutting the Astute's from a flat plate. Unlike buggies like the RC10, that had the front kick-up "molded" into the chassis itself, Tamiya added the kick-up via an molded plastic front bulkhead. It didn't really work for the rigors of competition.

So many others have tended to go the flat plate route more recently too, with this inherent weakness. It's comparatively just so easy to cut out of sheet material I guess. Carbon fibre gives the premium feel but shaped carbon as would be required must be multiples of the cost. It's a feather in the cap for the kind of unglamourous pressed aluminium chassis manufacturing method, I reckon. The obvious breaking point in so many chassis is right here, because, as well as being a join between two parts, by necessity it's narrow and has to allow clearance for steering parts through, and so it's the hardest area to design enough strength into. My own buggy design fails in the same place as the SA. You've got me thinking - maybe I could try CNC cutting a chassis out of sheet aluminium with a long nose and then screwing it down into a bending jig of some sort to kick the nose up. Could add a 3d printed Bulkhead spanning the kick up and the flat behind for rigidity without being relied on for strength in the same way. 

[Saito2]

Despite my love of Tamiya, this is where the genius of designs like the RC10 and Ultima come through. Merely adding walls in a tub formation like the RC10 strengthens the whole unit. Then to add a separate, replaceable front nose plate stamping with the kick-up bent in and brace that from the very front tip back to the tub walls with nose tubes makes for a very tough assembly. While the prototype RC10 tub was literally hand beaten over a wooden buck, the production versions went through a great deal of processes during manufacturing.

The Ultima ladder/girder chassis admittedly was probably easier accomplished with a simpler one- piece stamping technique, having the kick-up portion built in. The front end strength in the Ultima's case being in having the front end, through the front bulkhead mounted on top of the full length chassis, braced via a top "radio plate" running back across the top of the aluminum portion and tied into its top.

Chassis length/integration was where Tamiya often differed from other more race oriented designs. The Avante, Astute and Top Force series all have the chassis stop short of running the full length of the car, tacking the front end on (whether an 2wd bulkhead or a 4wd car's front gearbox) adding problems by making it a stressed member. Only the Avante series, with it robust front gearbox design and stronger plastics, pulled this off fully successfully in my humble opinion.

2 hours ago, BuggyDad said:

Carbon fibre gives the premium feel but shaped carbon as would be required must be multiples of the cost. It's a feather in the cap for the kind of unglamourous pressed aluminium chassis manufacturing method, I reckon.

This was the route taken by AE with the RC10 Graphite along the Losi JR-X2 (though the Losi car used a more budget graphite/fiberglass sandwich). The amusing thing was, AE drivers went back to the aluminum tub, most preferring the dynamics and response level of the aluminum. Losi then pioneered the composite molded chassis with the entry level Junior 2 (which eventually found its way into their upper level offerings) that ultimately became the way forward.

[BuggyDad]

1 hour ago, Saito2 said:

the prototype RC10 tub was literally hand beaten over a wooden buck

...which is music to the ears of the home tinkerer! 

[Kol__]

On 12/12/2024 at 11:13 PM, BuggyDad said:

Maybe if they're new plastic off the Blitzer tree they might fare a little better?

Yeah, could well be that as some of mine that have broken were older ones,  but it seem more that their design is better suited to the plastic chassis.

23 hours ago, Saito2 said:

at this point, depending on my drive to save money, I might be to fashion my own brace.

I was going to do just that, as I was running the Madcap front bulk head on my runner with the Astute chassis plate. I was thinking to replicate something similar to the Madcap brace, but have it come down and sit underneath the Astute steering arms (down to the deck, like you say @BuggyDad). Then when Xtra Speed recently released the alloy Astute bulk head my prayers were answered😃

So what shell will you be running on this @Saito2? I run the Madcap shell on my runner with the Asute chassis plate, and it looks great, but it leaves a lot exposed. I am going to try to marry up a new aftermarket Madcap shell with the Astute undertray. You did similar didn't you @naturbo2000?

[Saito2]

Personally, I'm leaning toward an Astute done up in original livery if I can justify the cost. Hoping TBG and MCI have Christmas sale like usual.

[naturbo2000]

I break any and all the plastic bulkheads (including using the Super Astute brace). I break any and all the plastic rear suspension mounts, including Blitzer Beetle.

I haven't yet broken pargu's bulkhead. I haven't yet bought alloy rear mounts.

Feel free to blame it on my driving.  You're probably right to do so. 

[becbec]

Love the madcap it's just a cool looking buggy here is my take on it

[Saito2]

11 hours ago, naturbo2000 said:

I break any and all the plastic bulkheads (including using the Super Astute brace).

Out of curiosity, where do the brace-equipped plastic bulkheads break in your experience?

[naturbo2000]

10 minutes ago, Saito2 said:

Out of curiosity, where do the brace-equipped plastic bulkheads break in your experience?

Thinking back,  my most recent breakage was to the shock tower mount (and I've only ever done that once). Prior to that I'm pretty sure it's always either at the flat-to-kickup bend,  or between there and the screws.

I've probably not broken that many,  bit it's frustrating enough that I'd rather pay to not have the failure. 

[Saito2]

Great scott! In the time it took my diff housings to get here, a trailer for the new Superman movie dropped. From what I saw, this iteration of the man of steel looks less conflicted and grimdark than Zack Snyder's take on the character. That's good because I have a feeling we'll need something a little uplifting by summertime here in the US. But I digress.

Here's a shot of the gearbox and captured in the that shot, some dreaded press-nuts...

I hate press-nuts used in ABS/PC plastic and for some reason the Astute in particular seems to have a bunch throughout the car. But we're not here to talk about fasteners, rather what some would call a flaming pile of a gearbox. I don't quite share that sentiment.

I actually like this gearbox despite the problems it gave people back in the day. It seems pretty compact, quiet and efficient compared to Tamiya's earlier offerings. Still, as always, there are teething problems as we'll see.

In the pic above there's several things of note. The 'box had a nice molded cover that removed fairly quickly and allowed quick gear changes and, a first for Tamiya, swap-able spurs. I preferred that cover to the quickly distorted often ragged-looking flimsy lexan covers found on RC10s. No slipper as you can see. The Astute hit just before slippers came fully into vogue. It does sport a ball diff which was all the hotness at the time. This one was dropped out of a quick access cover (a-la-Avante) on the bottom of the case. Good thing too, as Tamiya's new dive into ball diffs (though not first, the Celica Gr.B, Avante and Vanquish were there first) used a unique way of adjustment as we'll see later on. Oh, BTW, to those new to the platform, this gearbox sports a metal motor mount plate. That's a King Cab/Astute/Hilux MR deal. The lesser Madcap/2wd Saint Dragon (not the current T-shot based 4wd resurrected version) made do with a plastic one. The metal one's much nicer. Pick one up if you get the opportunity.

Below the spur lurks the gear support bracket. This was the first thing I recall folks complaining about when their cars got some mileage on them. Stormer Racing still makes an aluminum replacement version IIRC. Personally, I've found if the machine screw supporting the other side of that gear shaft through the case is kept tight (a little threadlock here helps) the plastic support bracket holds up okay. Granted, I only ran hot stock motors through these transmissions BITD so as always, YMMV. Next we examine Tamiya's take on a ball diff.

 

 

[Saito2]

And here it is! The ball diff that has sidelined so many of these vehicles. I decided to spruce this one up with some new diff housings (pictured) and see how long it last against the mad fury of a Torque Tuned motor.

Gutted and laid out for all to see. At the far edges of those line of parts are two shims (one per side). Tamiya, in their usual drive to eliminate ambiguity, used a bolt together affair with varying amounts of shims to adjust tension on the diff balls. Functioning properly the pros were the diff never really inadvertently loosened as there was no center diff screw to back out. The cons were shims meant a more limited adjustment range and the diff had to be dropped out the bottom and disassembled to adjust. In race situations, having multiple diffs shimmed in various degrees to swap around was the only way to make timely track side adjustments.

So what was so bad?....well, have a look:

Holy melted plastic Batman! Looks like that diff gear experienced a little too much slippage. But how did it really get that way? Well, to begin with Tamiya was very vague about explaining anything about ball diffs in the manual. The most you got was the suggestion of adding more shims to tighten the diff. That doesn't mean much to average kid dealing with his first ball diff and anxious to get the buggy built and out slinging dirt. The Madcap/Saint dragon oddly suggested no shims as a start point while the King Cab/ Astute called for one on each side. So, too much slippage just needs more shims to tame it down right? Not so fast as the next picture shows.

These darn cheap pot metal diff housings are to blame for the whole mess. Looking carefully at the pic above, one can see the housing is distorted. Too many shims just warped the soft housings around the three diff housing bolts that held the assembly together. Once the housing got like this, a thousand shims wouldn't help the cause. How many people would have figured this all out back then? Making matters worse, the number and size of the ball circle was pretty small and not very tolerant of abuse. Personally, I don't go over a shim per side in combination with good housings. That gets you in the right ballpark for diff tightness. Note: King Cab owners, please don't put giant tires on your rigs. The larger stock balloon tires add enough stress over the buggy ones as is. BTW, if there's any further doubt to the poor quality of the diff housings, check out exhibit B:

Look closely at the pic above and you can see a sliver of daylight above the one screw hole. That's how thin the casting was there at that point. Now how long would that housing have lasted if I hadn't caught that defect?

 

Well, here we are, all buttoned up with NOS housings. I'm probably due for some flack about having too much grease on that gear, lol j/k.  A couple extra notes...The picture with all the pieces spread out shows the nice, metal thrust bearings in the mix. They are Astute/King Cab pieces whereas the Madcap got plastic ones you inserted the balls in (that sentence came out risque, lol). Like the metal motor mount, they're nice to have when building up one of these.

Also, if you're starting with a used Madcap or Saint dragon, check the outer diff housing bearing surfaces. The lower end buggies used big bronze bushings here and they wore away at the diff housing at that point making the whole diff wobbly in the gearbox.

Finally, the original Egress used the same style of shim diff but with a stronger alloy used in the diff housings. Guess what? No problems! They aren't interchangeable with the 2wd versions though so no solution there I'm afraid. Overall, I like the whole set-up for what I used it for. Its a shame it was let down by those potentially faulty diff housings.

Next episode, I hope to get some parts from good ol' Tony's. They're floating around out there in the mail somewhere, fighting against the added pressure of Christmas gifts being shuttled about. Remember when we used to get in a car, drive to a physical store and actually buy our gifts like good little consumers? Man. I am out of touch. Until then, happy motoring.

[Kol__]

Good to see the progress with the gearbox and a nice write up covering some of the nuances of the design and its vulnerabilities👍

In some situations those press nuts are literally plastic splitters, but nestled into those recesses in the big chunk of plastic that is the gearbox, they're quite well suited, I would leave them in place.

The Madcap/Saint Dragon diff 'differs' slightly in that the thrust bearing carriers are plastic, so perhaps that difference is why it has no shims as a starting point in the manual.

I'm sure that once built up correctly by your capable hands the diff will be able to tolerate the Torque Tuned motor👍