Kol's Madcap Astute Mongrel

[Kol__ 3377]

Hi guys,

My favourite Tamiya RC car from my childhood was the Madcap. So this week I bought a well used vintage Madcap (Tamiya please do a frickin' rere!). It was used as a racer so has been heavily modified to include Astute parts and CV shocks of some sort. So that's good and bad imo. Bad in the sense that it's no longer an original car, although the seller did include the original tub chassis, and good in the sense it has some trick parts and more so I can actually run this car without really worrying about it.

So the spec as received is  - Astute chassis (carbon fibre?) / Carbon fibre shock mounts front and rear (Astute? don't look the same from my investigations) / CV shocks all round of unknown makes (looking at the angle of the rear wheels and the tyre wear the rear camber looks messed up to me) / different front suspension arms of unknown make / MTR Vtrac ESC / Reedy fury motor / Acoms Techniplus transmitter and receiver and servo / original shell and wing in ok shape (general wear and tear and a minor crack in body shell)

Plan is to strip, clean and service the whole car, including the gear box (I've downloaded a pdf copy of the original manual) and convert to 2.4ghz with new ESC etc.

 

 

 

 

[Kol__ 3377]

Cleaned up the shell, wing and wheels lightly...

 

[Kol__ 3377]

Here's the old transmitter that came with it...

The seller had lost the Rx crystal, so I order a new set and tested the buggy this evening

The buggy powered up straight away, with a modern battery connected loosely to whatever the badword those battery connections from the ESC are! Steering works fine, as does reverse, but it won't go forward. Assume something to do with the ESC, as when flipping the channel 2 setting on the transmitter the car went in reverse when pushing the stick up an again nothing when pushing it down. A bit annoying, so may look up the manual for the MTR Vtrac ESC to see if I can weed out the problem. However, as I'm converting to 2.4ghz, I may just not bother, assuming the problem goes away once the kit is replaced, fingers crossed!

Any advice with this build would be greatly appreciated!! Cheers

[Thommo 1217]

 

Great potential !  One thing that I can tell you is that (without the Astute under-tray and sometimes even with the Astute under-tray) the battery is going to fly out the side of the car the first time you roll it or miss a jump.  Battery security is inadequate for hard running with just the standard Astute battery holder.

You have an OG Super Astute chassis there with the extra holes for Super Astute battery holder and that is the solution as per Tamiya's fix with the Super Astute.

Also I would recommend using the OG Astute motor mount plate and a very well built diff that is not over tightened if using a powerful motor.  A silver can or GT Tuned motor on 2S is enough fun without over stressing the diff if you want a reliable runner.  

  

[jonboy1 2943]

the ESC might be a forward/brake type and you had the motor wires connected up backwards, as that would explain why it works in one direction and not the other. As you say, as you're going to change the ESC it's probably an issue that will resolve itself!

Those front lower arms aren't Astute or Madcap, but the rest of the front end looks to be with the exception of the upper camber arms, which would make sense as the madcap ones probably don't fit if the lower arms are a different length.

As @Thommo says, get the OG metal Astute motor plate (the Super Astute one won't work) as the plastic ones flex. I'm really surprised it hasn't got one fitted considering how much hopping up this has had!

Keep the updates coming - looks a really interesting beast this!

 

[Kol__ 3377]

Thanks for the input guys, nice one!!!

Yeah @Thommo the battery tray holder really confused me when I looked at the Astute manual before the Madcap arrived. I assumed it must be some sort of flexible plastic that lifts up to allow the battery in and out. Having received the car and seeing that's exactly the case, I'm slightly bewildered as to how Tamiya thought that was an adequate solution. What you've said confirms it, what were they thinking!? I had the same thoughts about fitting the Super Astute battery holders, as I read its a better weight distribution as well. Good to know those parts will fit my chassis, thanks I'll look to get those on order. Can only find them in the US atm though

Motor wise, thanks for the advice. I certainly want a reliable runner and don't want to run it into the ground. I'm unsure of the specs of the Reedy Fury motor that came in the buggy, so not sure if that's comparable to a silver can or GT Tuned motor. Hoping the Reddy might be fine, as it was run in the car previously, but that was apparently in a race setting, so not sure if that means it's abusive on the gearbox or not. Regarding 2S and Lipo in general, that's all new to me, and haven't got my head around that yet. Back in the 90's it was all Nicad and frustrating 10min run times as a kid!

You read my mind @jonboy1!! First thing this morning I had the same thought and swapped the wires round on the motor (wasn't sure if it would short circuit it or destroy it tbh! I haven't researched motors yet) but unfortunately no change, forward still didn't work, it just functioned in exactly the same way. Either I'm stupidly overlooking something really simple, or the ESC settings need tweaking. However, I can't imagine the original owner put it away with the wrong settings on the ESC. Anyhow, I've looked for a manual online but no luck yet. Today I ordered the below parts and they're arriving tomorrow, so might just not worry about this older kit... is kinda bugging me though! I like answers and solutions, not leaving things unresolved!

Got a plan to revive this puppy at some point over the weekend with a strip down, good clean, gear box rebuild with new silicone grease and fit all mod electronics and new rear tyres (the fronts, or suitable alternatives appear hard to come by and I'm not a fan of that weird line on the Super Astute front tires). I've gone the same or similar parts that I got with my Mad Bull, as I'm familiar with them. They are basic and not too pricey, and I'm not exactly looking to break any land speed records

ESC - Tamiya TBLE-04S - same as came in the Mad Bull box

Servo - Etronix ET2047 - 9.3kg/0.13s (which I believe is about standard for the average buggy?) / Digital servo with metal gears (an upgrade over what I bought for the Mad Bull)

Receiver - Etronix ET1095 - GFSK 3 channel 2.4ghz (same as came with the transmitter I bought with the Mad Bull, so should hopefully pair easily enough)

Rear tyres - Tamiya 53059 - good to go on the rears, front still a bit of an issue to find a solution atm

Silicone grease - Traxxas TRX1647

Shock Oil - Associated 35wt - I'm going to run the car as is first and then review a shock oil change. As I understand it the fluid is not hydroscopic, but you would assume that after sitting in a garage for 30 years it would be wise to change it out for new oil.

[Kol__ 3377]

Re the metal motor mount, that sounds like a wise choice. There are Super Astute ones available in the US, but does anyone know where I can get hold of a standard Astute one please, preferably in the UK?

[Kol__ 3377]

Here's the original chassis, rare, but pretty rouhg and dirty as badword from 30 years in a garage...

Cleaned up...

Not sure what to do with this shell now, so will probably just stick in a box for now

[jonboy1 2943]

19 hours ago, Kol__ said:

You read my mind @jonboy1!!

Yeah, - still not sure what you needed all that vaseline for though! 

19 hours ago, Kol__ said:

Rear tyres - Tamiya 53059 - good to go on the rears, front still a bit of an issue to find a solution atm

yeah fronts will always be an issue, never re-released and odd size. Keep an eye out for them on ebay and something will probably turn up eventually. The other option would be to go for something like the Wild One front wheels which opens up a bigger range of tyres, including some Schumacher ones that might take your fancy. If you have a look at my showroom I did this with my Jamie Booth replica.

19 hours ago, Kol__ said:

Re the metal motor mount, that sounds like a wise choice. There are Super Astute ones available in the US, but does anyone know where I can get hold of a standard Astute one please, preferably in the UK?

Again, set up a search on ebay as they do come up quite often. And of course, stick a wanted add in the sales section of the forum!

Might be worth getting a set of new bearings for it too, judging by the state of some of the metal bits they might be past their best too.

[Kol__ 3377]

Thanks @jonboy1, I think a different set of wheels will be the way to go. I want to stick with skinny ones on the front though.

Got the new electronics delivered and tested with the car, all seems ok

Started the tear down, man this thing is dirty!!!!

Some of the screw heads where just mashed, so I had to drill them out and use a small stud extractor on them.

I later discovered that these two at the rear of the chassis where going into aluminium on the other side and has corroded - the previous owner had replaced a couple of the plastic mounts for the gear box with aluminium hex bar.

Dirty, dirty, just plain dirty...

Clean, clean, clean...

Oh and it looks like we have a carbon fiber motor mount plate as well (somehow you knew @jonboy1!) ...

 

 

[Kol__ 3377]

On 9/23/2021 at 2:40 AM, Thommo said:

Also I would recommend using the OG Astute motor mount plate and a very well built diff that is not over tightened if using a powerful motor.  A silver can or GT Tuned motor on 2S is enough fun without over stressing the diff if you want a reliable runner.    

@Thommo I stripped the gear box, re-greased the diff and rebuilt it all yesterday. There where 3 tiny hex head bolts holding the diff together, I tightened these up until they were nice a tight. Are you saying that these bolts should only be nipped up?

Also, I used clear silicone grease in the diff and the rest of the gear box cogs. Would you suggest I actually need to use diff grease? I put a fair bit in the diff, on the plates/washers and the tiny ball bearings should only a little be applied?

Both before and after the gearbox rebuild, the rear wheels when spun by hand do not spin freely (like they do on my Mad Bull). There's resistance and noise when turning the wheels, is that just because the gearbox on the Madcap has a diff? Cheers

[Thommo 1217]

 

You would be better to use ball diff grease which is specifically for ball diffs and the amount on the balls and side plates is minute, just coated with no excess.  This helps the balls to grip the plate and not slide over the surface of the plate.  The plates are slightly rounded on one side from being pressed.  Make sure the flat side of the plate is contacting the balls.  Use at least one pair of shims (one each side) or two pairs of shims (two each side) and yes nip up the bolts and don't over tighten.  Use thread lock so they stay secure.  The diff action can feel a bit rough but I'm sure it will work alright with the right grease.   

[Kol__ 3377]

Thanks @Thommo, you the man!

I've ordered the diff grease, so plan is now to tear down the diff, clean it all out again, re-grease with diff grease and rebuild. This time only nipping up the hex bolts, I've got some blue thread lock around somewhere too

[Kol__ 3377]

The rebuild...

New rear tyres - Tamiya part number - 53059

A very successful trip to my local nut and bolt shop infuriate the guy there with many requests for matching versions of many different screws, nuts, bolts and washers. Plus some RC hex head screws from a local RC shop

9.3kg/0.13s Servo with metal gears fitted, it's a little taller/longer than the original, so swapped the servo mounting posts around and now it's just slightly not quite straight across the body, but I don't think that's an issue.

Fitting ESC and testing new servo in situ

The previous DIY standoff posts supporting the rear shock tower were bent and the screws were so rusted the sheared when trying to get them out. Manged to pick up some threaded hex tube at the nut and bolt shop, just had to cut them down to 25mm. Also replaced the DIY aluminium hex tube in the gearbox mount as they were poorly made. I've since ordered some black anodised ally replacements for the stand off posts.

Shiny, shiny...

Steering rod look ok like this guys? Or too much of an angle? Seems to function ok. Perhaps it would be better mounted to the other side of the servo posts? It would have more of an angle that way, but an open one as opposed to the closed angle it has now.

Since these photos were taken I've re-routed the motor wires in behind the shock

On/off switch mount location...

Moved the bottom nuts for the shock mounts from the furthest outer position to the inner of the three holes to reduce the, what I felt was, excessive camber - see pic in first post on this thread

Just the front arms spacers to fit when they arrive and to rebuild the gearbox to spec. And that's it for now, I'm going to run it for a while and have some fun with it before the bad weather sets in. I've got some future plans for it, part of the joy of this car is that it's so far from stock that I have no concerns continuing to modify it. Although it started life as a Madcap, when you look at the parts now it's actually more Astute than anything. Definitely doing a conversion to the Super Astute battery tray fittings and probably a new body shell and wing, and also possibly some new shocks.

Thanks for reading

[Kol__ 3377]

So I said I was done for the moment, but then this stuff just 'arrived' in the post...

Ball diff grease as planned

Spare conical washers for diff

Carbon reinforced front uprights/axles

25mm ally stand off posts to replace hex rod used previously

[jeekelemental 528]

I really like this hybrid, especially the dampers towers and the others custom parts that allow the use of the Astute chassis. Keep it alive it carries the 90s spirit made of handmade parts and creativity .

[Kol__ 3377]

Rebuilt the diff again and used the correct ball diff grease this time, thanks again for the advice @Thommo

Also fitted the Carbon reinforced front uprights/axles

Plus picked up a battered rear bumper/protector for £3

[Kol__ 3377]

So today I took the buggy for a test run, it ran really for about 10secs at a time, but then would just lose all power and roll to a stop. Switch the car on and off again and it would run for another 10secs and same thing again. It's a bit like when you've run out of battery, but if you turn the car on and off again it will have a tiny bit if power for 10-20secs again. It wasn't the battery as I put that in the Mad Bull and ran it for 15mins and it still had power. The only piece of electronics that hasn't been changed out is the Reedy Fury motor, so I guess that's next on the list. Any ideas lads?

[Grastens 2795]

Is that a stock Tamiya ESC in there? It may be that the motor exceeds the turn limit for the ESC; I believe the new ESCs can handle motors down to either 25T or 23T brushed, but the Reedy Fury seems to be rated at 12T.

A new ESC capable of handling low-turn brushed motors (not sure if Dynamite RC still makes the ECX1070, but I used one with a 13T motor without issue) will allow you to keep the Reedy Fury; otherwise, changing out the motor to a type 23T or above would solve it. But in the interest of speed, the ESC route would be more compelling...

And of course, there are now quite a few no-name ESCs that can handle low-turn motors, so it does not necessarily need to be expensive!

[Kol__ 3377]

Thanks @Grastens, that does make sense, however my knowledge on this stuff is a little limited at this early point in my modern day RC journey. The ESC is a Tamiya TBLE-04S, which was about £20 and seems to be pretty standard, basic level kit. I'll check out that ECX1070, thanks. For now I've fitted the Core 21T motor I had spare from another kit purchase.

With the Reedy Fury motor at 12T, is that likely to be too harsh on the gearbox and wil I get significantly less run time using it? Cheers

[kontemax 1725]

On 10/3/2021 at 2:18 AM, Kol__ said:

Rebuilt the diff again and used the correct ball diff grease this time, thanks again for the advice @Thommo

Sorry, this differential will never work.
Once tightened, the differential cases will deform losing pressure on the balls and the differential will slip.
Shims will then be added to prevent slippage and once tightened again the differential cases will deform further losing pressure on the spheres again.
It is a cycle.
The only solution is to use vintage Egress differential boxes, but you need to work one to fit the Astute gearbox.
You can also build them from solid aluminum with the lathe.
Anyway, once your differential no longer slips, you will break the teeth of the intermediate gear or spur gear and always and anyway the model will have terrible understeer.
The only choice is to adopt the Super Astute ReRe gearbox.

Max

[Kol__ 3377]

Well that sounds disappointing @kontemax, would that be the cause of this?...

[Grastens 2795]

1 hour ago, Kol__ said:

Thanks @Grastens, that does make sense, however my knowledge on this stuff is a little limited at this early point in my modern day RC journey. The ESC is a Tamiya TBLE-04S, which was about £20 and seems to be pretty standard, basic level kit. I'll check out that ECX1070, thanks. For now I've fitted the Core 21T motor I had spare from another kit purchase.

With the Reedy Fury motor at 12T, is that likely to be too harsh on the gearbox and wil I get significantly less run time using it? Cheers

Alternatively, a good number of TamiyaClub members drop in a Hobbywing Quicrun 1060 ESC and call it a day; those are rated down to at least 12T motors. They are definitely not expensive, either, and as a bonus are compatible with Li-Po batteries.

The Reedy Fury will definitely see shorter run times and more gearbox wear, but proper gearing and heat management (i.e. ESC fans, motor heat sinks, and other measures) will keep it happy  Best of luck!

[Thommo 1217]

On 10/6/2021 at 6:07 AM, Kol__ said:

Well that sounds disappointing @kontemax, would that be the cause of this?...

 

That could be stone damage or it was run with the motor becoming loose.  Don't worry too much about the diff.  If it does slip really badly and won'r run, we can discuss that when it happens.  There is a few ways to work around, including locking the diff with fiber washers or poster gum if you have to.  As Max mentioned, there can be knock on affects too like breaking the counter gear support so you have to be a bit careful. 

 

[Collin 1956]

Hi there. This is really a great guggy you got and I am glad you did not over-restored it. I love it so much that you still can smell the racing history of this buggy. Shiny shelfies are nice but you can never immitate a vintage runner/racers spirit.