JennyMo

The Mega-bug! - aka. 'Sinclair' [the C5]

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I'm sorry - that is a rather pompous title I know (and it will almost certainly change as this build evolves..), but I've had an idea that was too good not to make start on, and subsequently share... so needed a thread title!

Some of you will be familiar with my Fro-Sco (Frog/Scorcher hybrid) project which was one of the first Tamiya mash-up vehicles I built; and which evolved over the years - including grafting-on a whole SRB front-end to the Frog chassis - before I ultimately decided to sell it as part of thinning my collection prior to finally moving to the US earlier this year.

Link to the Fro-Sco in my showroom: here.

While I've been concentrating on building more crawler style 4x4 vehicles recently, I've always had a soft-spot for the [Tamiya] Beetle body - and indeed it was the original Sand Scorcher (back in the early 1980s) which got me interested in the whole RC thing in the first place - so I have to admit, I now kind of miss having a Bug on the shelf...

 

Which neatly brings me onto my latest idea - a 'Fro-Sco Mk2' as it were - something even more extreme/and mechanically refined/scale than the original, but using a similar ethos in that it will combine [what I consider] the best of the SRB Scorcher: the front suspension and the body-shell; while eliminating the weaker elements: erm, the rest of the chassis and the short-travel rear suspension - and replace all that with something far more extreme looking and potentially more dynamic too.

To be honest, it's already something I've been considering ever since I started building the SRB Cage Racer - which mated SRB front and rear sub-frames using a custom allot chassis, to a Vaterra Twin-Hammers cage assembly, creating what is essentially a two-seater 'Rough Rider' style SCORE buggy, complete with full interior and lots of scale detailing.

Link to the SRB Cage Racer in my showroom: here.

Indeed at the time, I thought that with a bit of Dremel work, the Twin Hammers cage would actually fit very nicely inside a Scorcher shell - the main cage fitting neatly inside the cabin, while the rear rails would essentially extend out through the rear window/C-pillars and over the rear-mounted engine - ideal for mounting a spare wheel as it were...

Sure enough, revisiting this idea in the last few weeks as revealed there are actually loads of people who have had a similar idea out there in internet RC land (there are very rarely genuinely new ideas these days I know) who have to a greater or lesser degree, successfully mated a Scorcher body to a Twin Hammers chassis/cage and running gear...

However, I have yet to find anyone who has junked the IFS (independent front suspension) and 4WD as part of these builds - and why would you? - after all the 'Hammers is an excellent 'rock-racer' and not bad in more technical terrain too... but it's not really very Baja/Class 5, nor particularly scale with typically huge 1.9 or 2.2 wheels & tyres and the extra wide axles/long wheelbase of the original Twin Hammers chassis.

So this is my plan:

i-63hFFSc-XL.jpg

photo. assembling the core components... and then changing my mind a bit ;o)

When I drew up the initial spec for this build, I knew I had to utilise the Tamiya SRB scale front suspension assembly (as I did with the Fro-Sco and Cage Racer) as I consider it quintessentially 'Baja' - even though there is not a huge amount of travel, and indeed you can only fit a maximum of 70mm shocks on the front without extending the towers - and even then the cast 'bump stops' limit the overall travel anyway*

For info. the 70mm RC4WD super-scale internal sprung shocks are perfect to replace the original curly springs and dampers on the front of an SRB, with only a little grinding required to the original spring tangs to ensure the shock body clears:

i-h7WHwkw-XL.jpg

i-ddDW4tK-XL.jpg

 

The bodywork would of course be a baja-bug Tamiya shell - in this instance the Monster Beetle version rather than Sand Scorcher (white) or Blitzer Beetle (black), primarily as it was really cheap on Ebay (less than $16 shipped!), and I won't be using many if any of the other parts you get with a complete body-set anyway. Indeed, while this vehicle will remain instantly recognisable, it is going to require some pretty extensive wheel-arch work to fit around the rest of the underpinnings I have planned...

The rear end for example is going to be very much mix-and-match - and fundamentally I wanted to use a [scale] live rear axle on long trailing arms, and long-travel coil-over shocks on the rear (fortunately I already have a number of sets of these discarded from my various crawler builds over the years). Now of course this is also what a lot of the Twin Hammers [chassis] based builds look like, but it is not inappropriate for a 'unlimited' class desert buggy once you decide to junk the original VW engine and trailing arm suspension (sorry Toykid, but this one is getting more than a flat-4 air-cooled lump in it ;o)

However, using a traditional solid axle and radius arms immediately threw up a packaging problem - in that to have a decent length prop-shaft, either the gearbox would be were the seats needed to be (if this is going to have a scale interior, which was certainly always the intention), or the wheelbase would have to be significantly extended rearwards... not an issue itself since the Twin Hammer cage extends way past where the original rear axle line would be - and where I intend to mount a pair of spare wheels vertically this time (compared to the SRB Cage Racer, which has a shortened cage and single horizontal spare directly above the ToyKid scale VW engine).

cont.

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cont.

Now in the photo above, the actual Twin Hammers cage sides have been cut down (they are the left-overs from Lisa's Cage Crawler, the underpinnings of which eventually morphed into the Defender 90 Truck-Cab you may recall), and are really only being used as a template so I can work out the final wheelbase and component layout... I've already ordered a complete cage kit from Ebay (edit. and delighted that it arrived this afternoon!) which means the final build will have a complete internal roll-cage including door bars and a dash rail.

Initially I considered tying everything together with a flat alloy chassis plate - either a simple custom fabrication as I did with the SRB Cage Racer, or else modifying a commercially available chassis - for example there is a nice CNC machined alloy one on Ebay that fills the complete floor of the Sand Scorcher shell - and by using a flat alloy chassis, it would be easy to drill and subsequently screw the various trailing arm brackets and gearbox etc to the floorpan...

However, it was soon clear that so much would need to be cut away, that it didn't make sense to buy an expensive CNC chassis plate, and that ultimately, even a custom one cut from alloy sheet was going to limit how the engine and gearbox would interface with the rear suspension and axle... basically, whatever way I looked at it, there simply wouldn't be enough room to have any meaningful articulation or travel using the SCX10 gearbox I'd already procured for the task*.

*Guess I'll just have build a cage crawler or something with it in future then eh?

Then I had a brainwave.

 

Sand... rails!

My most recent project has been a leaf-spring Jeep built around a pattern Trailfinder/Gelande style rail chassis (surprisingly affordable via Ebay) - and fundamentally ideal for scratch-build projects as the multitude of mounting locations all along the chassis rails means you have an almost infinite number of suspension, gearbox and engine pick-up points, and plenty of scope for drilling, tapping and generally making your own mountings where required.

Being essentially a pair of rails linked by a series of cross-members and held together with M3 screws, it also means it's perfect feasibly to narrow or widen the chassis as required to fit your intended axles and other components - plus, using a longitudinally mounted motor and planetary gearbox (as I have in the YJ Jeep and Lisa's D90) makes for a very compact and low-profile engine installation, and could easily be incorporated in the rear of the car - as I had always planned (this being essentially a mid-engine car, with the engine where the rear seats would be).

The only issue was these gearboxes are typically a 5:1 ratio (ie. very slow, for crawling) plus there would be an issue about how to get the drive from the gearbox essentially 180° back to the axle mounted directly underneath.

i-8k7Q2md-XL.jpg

photo. initial mock-up, using a 164mm wide (from pin to pin) scale 'Yota' axle, alloy Axial Wraith lower links and a selection of rods and ends I have in my stash. The dual-spring shocks are 100mm long, removed a while back from Lisa's D90.

cont.

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cont.

Fortunately my recent experience with the Jeep and D90 again paid dividends here - the separate central transfer case I used has a 2:1 ratio (therefore halving the gearbox output to further improve slow-speed crawling ability) - with a single input shaft coupled to a fore and aft output shaft. However, it dawned on me that if I were to mount this upside down in the Beetle chassis, then the gearbox could drive one of the output shafts [as an input], and the original input shaft would then become the single RWD output shaft for the axle - with the benefit of doubling the speed of the gearbox instead - bingo!

 

Mounting this style of transfer case upside down also has the benefit of keeping the interior floor nice and flat (as it will hang down rather than stick up - typically into a transmission tunnel on a scale 4x4 build), which in turn will help to reduce the prop-shaft angle to the axle - and while this will reduce ground clearance under the chassis rails a touch, the chassis rails themselves are actually higher than where the floor pan of the body would need to be anyway - so essentially the rails will be inside the cabin (where they can most likely double as seat mounts), while I can still fabricate a completely flat floor pan for the vehicle, other than where the output knuckle and prop-shaft extends...

You know I really think this is going to work!

 

So while I now wait for the postman to deliver the newly ordered gearbox and transfer case assemblies, this is where I'm up to:

 

i-cRNvkkF-XL.jpg

photo. if you can imagine the transfer case will be located where the tubular cross brace [above the block of wood] currently is, and the motor and gearbox between the chassis rails between the suspension towers.

 

i-zPT925w-XL.jpg

photo. approximate rear axle location - this is likely to be moved a little once the front suspension has been bolted to the chassis, and the front wheel location in the 'arches' defined.

 

cont.

 

 

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cont.

For this initial mock-up, I elected to narrow the chassis from 72mm to 50mm between the solid rails (using some 6mm diameter M3 internally threaded rods as braces) - which is about as narrow as you can make it while leaving enough room for the motor and gearbox once their mounting tabs have been trimmed to fit. It also means that at the front, the SRB assembly needs to be widened by 10mm (using an 85mm rod together with a 2mm spacer compared to the original [77mm long] rod - plus ultimately replacing the upper and lower tubes too with corresponding longer pieces cut from alloy stock), and the chassis rails will then fit perfectly inside the uprights.

 

i-GWhLMWQ-XL.jpg

photo. lengthening the tubes so the uprights fit around the chassis rails also has the benefit of increasing the front track width to more closely match the rear axle too.

 

i-JKW4mD2-XL.jpg

photo. currently the wheelbase is not too far off the original - 280mm, so similar to the SRB Cage Racer.

 

Obviously the 415mm long chassis will need the forward arches section cut off so that the SRB front suspension assembly can then be bolted directly* to the underside of the horizontal centre rails...

*note. While there is currently a degree of disparity between the front and rear axle height of the car (the front of the car essentially being lower than the rear if it were actually on it's wheels) - this ought to be able to be dialled up and down to a degree using spacers between the chassis rails and the SRB subframe brackets to ultimately get a more even balance/stance.

 

Right, in that regard I fear we now have an appointment with Dr Dremel. Wish me luck!

Jenny x

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Not read all this yet but from title I thought it would be based on the new trike to make a C5.

Will read properly later .

Good luck 

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I, too, thought it was a Sinclair C5-style vehicle, but reading through all your notes quickly dispelled that notion, and opened up a really interesting and unique one! Mind you, I was just excited to see another new JennyMo build thread :D

The use of a solid axle is also interesting, but as you wrote, it is definitely in the ethos of a true Unlimited-class racer!

I look forward to following along as it all shapes up - including the detailed posts! I wonder who will be driving...

Edit: and NOW I see what you did there with the name! Nice one :P

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A little more work today...

Since the Vaterra cage arrived in the post yesterday, I thought I'd assemble the main parts and see how it fits inside the Scorcher shell:

i-66QwSBN-XL.jpg

Pretty well as it turns out - in fact I'm surprised just how well it does fit inside the body - almost as if it was made for it!

I'd say if you are looking for a full internal roll-cage for a Scorcher build (even if you decide to cut off the rear frame extension), then this is a really good option - especially for around $22 on Ebay.

i-4PqqnfB-XL.jpg

photo. cage is almost exactly the same height from floor to roof - all you'd need is a pair of [6mm?] spacers on each side to mount the cage to the floorpan/chassis.

 

i-pXWz52x-XL.jpg

photo. (previous cut version) - you can see here how well the main cage follows the A, B and C pillars.

 

So with the promise of a successful combo, it was time to fire up the Dremel!

i-LcBNRZT-XL.jpg

photo. 4.5mm pilot holes drilled for Dremel reaming tool to fit - note I also cut a slit between the two holes with the cut-off wheel to help the reamer head follow a straight line (see below right).

 

i-9Wgtj9v-XL.jpg

photo. initial pass with the reaming head (on left), before widening and using a file to finish.

 

i-bBqCd32-XL.jpg

photo. test-fitting my loose cage sides - looks pretty good doesn't it?!

 

cont.

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cont.

i-9JpMmrp-XL.jpg

photo. similar to the first photo in the above post, but now the rear of the cage exits through the C pillars either side of the rear window...

 

However, while I was initially able to retain the complete window surround with some judicious Dremel-work, ultimately I felt it would be more successful visually if I simply widened the rear window so that the cage exits through the full width:

i-8GQZXsJ-XL.jpg

photo. front arches completely removed, and rear arches trimmed in the Fro-Sco stylee.

 

So, this is basically where it stands now - already looking much closer to how I envisioned - although I still have to work out how I'm going to fix the front suspension subframe to the main chassis rails...

i-bkjPrtK-XL.jpg

photo. Wheelbase is currently 285mm (approx 11.5 inches) in this picture - hopefully I can reduce that by 10-15mm once the motor and gearbox has been installed.

Currently I'm considering a flat chassis plate (similar to that which I cut to mount the SRB front end to the Fro-Sco chassis), and a pair of vertical spacers to brace against the arch of the chassis rails above. This would then allow me to position the subframe more forward in relation to rear of the chassis - freeing up valuable space inside the cabin for seats in front of the upward curve of the chassis rails:

i-bBKrNGk-XL.jpg

And of course using a flat plate at the front to mount the front suspension subframe will also mean it will be simple enough to continue that as a whole floorpan (much as I did for the SRB Cage Racer), filling in the whole of the underside of the cabin, while the trailing arm suspension extends behind.

More soon!

Jenny x

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:o this is going to be truly fab!

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7 hours ago, Mad Ax said:

:o this is going to be truly fab!

Hee hee - I hope so!

In that regard, shall I paint it yellow with a #4 race number?

(with Gordon Willy driving ;o)

Jx

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3 hours ago, JennyMo said:

Hee hee - I hope so!

In that regard, shall I paint it yellow with a #4 race number?

(with Gordon Willy driving ;o)

Jx

If he did, he would have called it FAB :P

However, Wild Willy's cartoonish proportions would lend themselves well to a Thunderbirds-style driver! Hmmmm...

The cage is spot-on - that looks like a proper Class 5 racer already!

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On 4/4/2019 at 7:06 AM, Grastens said:

 Mind you, I was just excited to see another new JennyMo build thread :D

 

Agreed!  A new build thread by JennyMo is always a good thing!

Looking forward to follow this one for sure!

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 ( Vaterra Roll Cage Set with Aluminum Panels (290mm) Ascender VTR230055)

 

is is that the roll cage you are using?

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2 hours ago, Busdriver said:

 ( Vaterra Roll Cage Set with Aluminum Panels (290mm) Ascender VTR230055)

 

is is that the roll cage you are using?

 

Hi Busdriver - no, although funnily enough, that is the one I used for the back of Desmond (narrowed to fit the narrowed HiLux cab in my showroom: here.

The cage for the Scorcher is actually the Twin Hammers upper body parts - it comes as a separate pack pn. VTR230000

If you search on Ebay for 'Twin Hammers cage' it should pop right up - although it appears most of the retailers are US based rather than UK... you ought to be able to order it through a shop in the UK though?

Hope that helps...

Jenny x

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A quick update now that the planetary gearbox has arrived...

I've chosen to swap my Tamiya Torque Tuned motor from the Jeep (as it is actually directional, and I realised the transmission layout meant it was running in reverse when going forward in that installation), which means I now have a hearty 540 motor for this build - that ought to run in the correct direction once the 180° transmission layout is installed - result!

So I bolted the motor to the gearbox, and set about trying to fit it in the rear of the car:

i-pwqXggZ-XL.jpg

Turns out it is a perfect fit - and even better, because I'd reduced the width between the chassis rails to 50mm, the supplied engine mounting brackets fit perfectly on the outside of the chassis-rails, and line up with the original holes in the gearbox mounting plate without needing to cut or drill anything - bingo!

i-C4nXz2n-XL.jpg

I also took the opportunity to rejig the upper links (in an effort to have them clear the bottom of the motor on full compression) - and ultimately also repositioned the lower links on the chassis effectively shortening the wheelbase by 12mm. The result is that there is more articulation (almost fully compressing the 100mm shocks), and the upper links actually clear the motor in that side to side orientation - and only just touch the bottom of the motor under full [equal] compression. A bit more tweaking ought to see it clear under every scenario, although this is always going to be a balance since I want the motor sitting as low as possible in the chassis ideally, and level - as my intention is to fit a scale engine cover over it - particularly as it will be visible through the rear window.

i-ZRf9cQZ-XL.jpg

photo. new longer upper links, currently only touch at the axle end on the very end of the motor housing during full compression.

 

i-r3fcBKP-XL.jpg

photo. this will look cool with a scale V8 engine cover I feel!

 

i-q5TLSXS-XL.jpg

photo. mock up with new wheelbase - now currently 270mm or thereabouts.

 

Ultimately I'm going to have to wait until the 2:1 transfer case arrives - as the prop angle may be a bit severe - and if so, the engine will have to be canted forward unfortunately, which may look a bit odd with the manifold cover on, we'll see...

The other thing I want to try before I finally cut the chassis rails and fabricate a floorpan, is to swap everything around and see if I can't get a slightly lower profile installation using the curved 'front' of the chassis as the rear instead - the only issue may be the fewer number of mounting holes at that end of the chassis may limit the perfect layout?

More soon!

Jenny x

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Your builds make it look like most of us are just playin' at  RC cars....so annoying!

Another wonderful build coming our way...amazing work Jenny.

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On 4/6/2019 at 3:21 PM, Bromley said:

Your builds make it look like most of us are just playin' at  RC cars....so annoying!

Another wonderful build coming our way...amazing work Jenny.

Bless you Bromley... we're all just playing of course - some of just use a bit more paint and metal that's all ;o)

Jenny x

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I got quite excited to see this as the title says Sinclair C5. I have a C5 in pedal only form now and currently on the hunt to electrify the little beggar. Great build again Jenny and you certainly give confidence to us girls to build! Jo x

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Jenny, could you do me a big favour and measure the diameter of the roll cage tubing. I have one on order but want to fabricate some other bits and bobs in same thickness before it arrives. Following build with interest.

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5 hours ago, Busdriver said:

Jenny, could you do me a big favour and measure the diameter of the roll cage tubing. I have one on order but want to fabricate some other bits and bobs in same thickness before it arrives. Following build with interest.

Hi Bus' - I don't have my micrometer to hand (it's still in transit from the UK), but eyeballing it with a metal rule it's more than 4mm but not quite 5mm diameter - so I'd say 4.5mm, which would equate to 45mm in 1:1 scale, so pretty much on par with a real roll cage then.

Hope that helps...

Jenny x

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