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Sandrail ..... time for another project!


Nitroholic

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I can't help it ... I like sandrails! I don't live anywhere near any sand, but there is something about hte way they look that just appeals to me.

 

I owned a Tubedigger one, and it was quality. Got sold on in the end after the rest of the car fell apart around it.

I've tried bolt on cages, and have made a decent one out of nylon rod which works well and looks OK .... but:

 

the more I look at cages bolted on to the stock chassis the less I like them. You can't hide the chassis, no matter how you try. It dominates the layout and it dominates the shape. It means the servo mounts are where they usually are, the radio tray and fuel tank etc.

When I built Shorty, I found life so much easier once I binned the stock layout and just found parts that fitted. Running a smaller square section tank has been no hardship, and some flexibility over steering setup was also a plus.

 

So....with a free weekend, 6m of 10mm steel tube in the shed, a beefed up tube bender and some assorted other bits and pieces, it's time to get serious!

 

so.....lets start with the design ideas. There are a couple of 'basic' styles I have to decide between first of all.

 

1) Completing a 'cage' 4 seater style.

5b-sandrail-large-02.jpg

I like the backend, and I like the really low slung front..so if you imagine that with a proper underside...that's one option. Best looking thing I have seen, though, is the RC4WD smaller scale shape. Clean and tidy...and I am sure I could replicate it in 1/5

112232323.jpg

 

 

 

2) Another look would be the ultra skinny, lean mean look. Actually easier to build....and has that look you just cannot get with a stock chassis underneath.

sandrailg3.jpg

The pictured car is a work of art, as hte guy built his own gearbox, drive ...everything! Impressive....and not something I can do. I'm looking more at the styling and there would have to be compromises.

 

3) The last look which i absolutely LOVE in the real full scale is the classic 'Fisher' buggy look.

DCP_1094b.jpg

Throws up some real design issues as it's intended for a beetle swing axle front end, hence the very low slung flat front end. No shock towers allowed....hmmm...now there's a challenge! How to make that work without ruining the lines.

 

 

Some design decisions have already been made.....

 

1) I will retain the rear chassis plate.

This will allow me to easily use the stock engine mounts, gearbox and rear suspension arm setup. The shock towers will go, but the rear brace etc. has to stay to preserve the integrity of the drive-line. The plate will also brace up the rear chassis section, which can be slimmer under there.

 

2) I'm going to go for an FG steering setup on the above designs excelt the last one... Upside down servo and FG servo saver assembly is much more compact. Just need to bolt a flat ally plate across the front rails. I already have the parts I need for that, so it's all good. I would stick with HPI layout if I went for the Fisher though, as it's lower profile.

 

3) I'm going to buy a smaller fuel tank as per Shorty. It's such a neat layout, and takes another step away from stock. Means I can tuck the tank and radio under the air filter to leave the maximum clean space to show off the cage.

 

First task....play with some designs and mock it up with an assortment of wire, tape, plastic tube etc. and see what will work. Going to strip down the Baja for a clean anyway .... so it's the perfect time.

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Hi Nit, long time no hear???

You still doing projects. Lol :)

Not been on for a long time!!!

Think my lipo batteries a goosed. Looks like they have ballooned...

Maybe time for new ones and more research again.. Forgot everything

Anyway keep up the good job and nice to see someone I know from back in the day

Edited by karlo888
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Great stuff. That big build looks madd the guy has flipped the engine too hasnt he. I cant see a pipe tho. I agree with you on sandrails looking the bomb. Good luck cant wait to see it come together.

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That last one holic !! 

 

sandscortcher front end, no shock mounts you say ..........

riight need to draw up a little diag scribble .......... 

inboard shocks laydown style to a cantiliver push bar system leading to front wishbones,

think F1 inboard front end canti system, will take a few drawings and scribbling but it would work. 

 

best outta the bunch is the stretched baja sandie . 

most easey welded up is the class 1 kraken style body ( first image), but twist it up

have a set of dual large bore shocks on the rear spring and springless. 

also have them mount hi-tailed not so low down as the second image. 

 

the last image is more like a autoracer class 1 buggy just stripped of panels and front end dropped down with solid none

damped, 

 

so on that note  take the first image cage, and meld it with the second image to give a true scale kraken.

the baja is lovely but the stretch just does not work with me, class 1's tend to be short fat stubby racers

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TamiyaCowboy .... like your thinking :)

 

Been tinkering with designs, mocking up bits in Nylon etc. and it has brought a few things into focus. I don;t have a lot to show for it so far, but I have an idea what can and can't be done based on the limitations imposed by the stock engine layout. It's not a 'greenfield' job :)

 

1) aka pictures 1 and 2. I like the clean flat rear deck on picture 2, but due to the layout of the Baja shocks, they end up stuck up in the air with nothing to mount them to, or you have the stock towers stuck up there looking daft. Picture 1 uses a higher rear tube setup, which does give you somewhere to weld on an upper mount. So...if you imagine the top picture with just the rear section merged onto the front/middle of the second picture .... that would work. I am also looking at ways I could fit a pair of dummy seats in the front for a 'passenger' or two :)

 

2) Picture 3 looks lovely ... but I cannot replicate that back end. Several things get in the way....

 

a) Exhaust. I have a Dom on at the moment, and this design is very short in the rear....so the Dom would be hanging in space. I side pipe would be the only option....and I want a few more options than that! A sidepipe would have to sit outside the cage too

B) Shock angle.. using stock mounts on the arms, you cannot angle the shocks forward. I have some 12mm box that would fit perfectly in the arm...to which I can weld a mounting....but the upper arm is still in the way. I would have to replace the upper arms with a beefy pair of turnbuckles running behind the shocks as in the picture. Should work...but....

c) Putting the bits where I want them obscures the spur gear cover. Whatever I do...I want to be able to work on the car easily. Needs more thinking time there.

 

3) You're talking Revo style shocks and linkages. Easy enough in theory....if I can get springs to suit. It's just an L shaped pivot. Not sure I'm brave enough!

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BlackRockClass1_large.JPG

 

 

this type of layout on the rear tower unit, hi side mount point, yep shocks on baja and likes are usually upright, so i was thinking a

U type fixing alowing the shocks to lay back somewhat. 

 

 

you could always go a frankenrail 

 

1018_2lo.jpg

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Think I would need to go swing axle to do the twin shock thing justice. Which is tempting..... Not sure what I would need to make suspension arms strong enough. I have some 8mm studding. Pop a rod end on either end. Could fabricate something to hold the axle and bolt on, with a third tie-rod at the top. Question is...would it just bend? I could weld up some tubes to make an arm.... but the same goes for that. In the meantime...

 

First thing I had to do was clean up the Baja. Been a while since I had it completely apart, and it's amazing how much muck accumulates under the fuel tank and radio tray! The pile of dirt was just from that!

day1_zpsa481065a.jpg

 

The exhaust has got a good clean up, and despite caked on mud, it was actually rust free. Not bad for a cheapo clone.

 

Been playing around with some of the ideas TC has kindly thrown my way, whilst agonising over making things fit around the Dom etc. I looked at some of the fitting kits for shocks on the Savage and some of the things I did for my FG sandrail where I had to frankenbuild the front end to get the width I wanted. I came up with this...

day2_zps7946e06a.jpg

 

It basically allows the shock to sit a bit higher and a bit further back. Like that...it can angle forward without hitting the upper arm. Obviously, this is just a rough bodge up... but I have some 12mm square tube that is a perfect fit in the gap in the arm. Weld on a cross piece, with another square tube behind the arm. Bolt through the middle into the arm. Possibly extend a brace up to the sway bar mount too if I need to. Under compression, the arm presses against the bracket, so the load is transferred. I can vary the position of the shock with a welded up version, but the main thing is I can get a bit of angle on the thing without clearance issues.

 

With a simple up and over tube, the shock can tuck inside as well. The tube will need bracing down and across, but the idea is to do away with the stock shock tower assembly and to make the back end of hte truck look as clean and flat as possible.

 

day3_zpsc95ded0a.jpg

 

The whole section will need to be removable for engine access. ....so the lower mounts will slide over tubes bolted in place at the rear....and the up and over tubes will either do the same or be bolted on

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looking good. 

 

yep i see where your going on the rear mount shock, the top roll rod , maybe have this curved,

a little  then a little hoop x2 , these little hoops could be the top shock holders . inboard ofc

but give that meat to the top of shock and lower risk of a top blowing. 

if your running piggybacks and tubes can run those along the rear inside top rail ;) 

 

oh and she need a set of rear paddles !!!!!!!!!  and testing in the local kiddies play area sand pit :)

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Well...steps forward...steps backwards.Called a halt for the weekend as it's too damn hot to be welding!

 

Steps forward....

 

The design I want to finish up with has started to gel a bit now. I know what features I want, and I know roughly how I want to lay it out. That's a big step forward largely thanks to some input from TamiyaCowboy, who got my grey cells back into thinking mode :)

 

I have started cutting a welding a few trial pieces, and it's not gone too badly. I made up arear arm to see how things might look, and I like the work so far. My welding isn't pretty...but hitting bits of it with a hammer didn't shift a weld any, so that's all good. Going to need a fair bit of cleaning up before it looks pretty though.

 

sr1_zpsbf0fe554.jpg

 

The shocks will mount like this.... with a spare damper only for the 'look' more than anything else.

 

sr3_zps027138f3.jpg

 

With a wheel fitted up, I have 6mm clearance all round, which was less than I really wanted....but OK. Just means I couldn't remove the extenders, not that I would want to anyway.

 

sr2_zps02a68678.jpg

 

I bodged up a mount so I could test the suspension movement next. And at roughly this point...the step backwards slapped me in the face. There is no option really, but to bin this arm and start again.

 

Why?

 

Well...lets look at the geometry again. The top linkage acts as a camber arm, controlling the level of camber at rest. With any trailing arm setup, as the suspension compresses, the camber link will tend to pull the top inwards, increasing the camber. Now...when I setup the bottom axle mounts, I completely forgot about this and have only allowed for a few degrees of camber, which is all you need for normal setting up. Soon as the shocks compress though, the upright will jam against the suspension arm, and the camber link will tear itself apart, At best, I am going to get horrible wear on the pivot.

 

So....Time to build Mk II suspension arm. I am considering using a couple of ally rod ends as mounts for the lower pivot to get some adjustability, but we will see. I have made up a jig for the essential bits which I will just need to adjust to give a bit for camber. I only need 5mm more clearance to get all the movement I need. Will also give me more clearance. Will also be able to build a few other tweaks in to neaten things up second time around :)

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a sketch of a trailing arm carrier 

 

milo3T1.jpg

 

 

notice they have a fixed camber. 

 

think of half a see-saw  , the center piviot is our chassis link , the end of the

see-saw is our wheel hub carrier and inbetween we pop a couple shocks.

notice how the arm is shaped , we have a flat end with rod hole all the way alone with a matching hinge like fixing.

 our arm is straight along with the wheel, we add a little clearence for the wheel/rim not rubbing the arm.

 

the end is usually a bearing carrier then your cvd hub slips in, i have left out some bracing so you can see how it kinda works.

its more line a floating cvd joint you see using trailing arms, if some camber is needed its built into the bearing carrier/arm.

 

hope this doodle will help you look at ideas on fixing the camber lock ( maybe a L bracket link or something )

Edited by Tamiyacowboy
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hmmmm....

 

Well...I was having a bit of a think, aided by the last of my chilli beers ( must get more ... ice cold lager with a chilli floating in it giving a spicy hint...heaven ) and it hit me. I took apart the spare uprights I have ( alloy ones ) and the bearing carrier centre section is seperated. Bolt this through a pre-fab 'box' and I can create exactly what I need on the end of the arm.

 

I want the arms to angle out from the centre of the chassis, which means I have to have a dog-leg in the arm.... but this is needed as the hub sits right inside the wheel. Can't do much about that. If the wheels had more offset, I'd have more options. I need to make up a box like asssembly which I can drill and bolt the bearing carriers to. They bolt through the toe-in adjuster plate, which I will retain. Means setting for zero camber, and leaving it fixed.

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Good thinking batman. 

 

its more of how do i use this, instead of how do i make one of these. 

maybe a small box section rail thin profile say 4mm x 2mm , tack this onto the rear arm and drill mounting hole for a long bolt 

right the way through a kinda sandwich, small brace behind to stop it falling over.

 

as for the beverage, add a man made greenhouse and grow your own chillis.

manshed converted into a mini brew yard ( couple hombrew kits) and your

never gonna go thirsty. youngsters replace the beer kit with a sodastream ( they are wicked awesome, the blue stuff )

Edited by Tamiyacowboy
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Another epiphany moment .... which has slapped me in the face.

 

I couldn;t figure out what was missing in my attempts to figure out what was what on my susepnsion and how it all works on teh real thing. And the more I think about it...the more I realise that's what I am trying to do.... make one like the real thing.

 

So...swing axles.... looked at a few pics while I was bored at work, and it hit me.

 

I know a Beetle back end....used to own one a while back, and Beetle transmission is the heart of the rail design. I was looking at this picture...

 

20i6xcw.jpg

 

and I was thinking how skinny the swing arms looked....until I remembered. The axles and CV joints take the strain. Great big axle tube.

 

So...I need to replicate that setup again with an arm running out from the gearbox pivoting in line with the driveshaft. Could make a large diameter tube and pivot it co-axially with the dogbone pivot....and attach that to the axle upright section. Maybe a pair of rod ends either side as pivots for the tube... or just run a tube under the driveshaft with a rod end at the chassis side, welded to the upright section. Sure I can rig up something.

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they are not tubes buddy they are solid axle splines leading from gearbox to the rear wheel hubs.

heres a better picture of what the vw like rear end would look like 

 

Sandrail002.jpg

 

 

edited idea, 

 

imagine a crawler transferbox.  we shove this  on the rear of the baja chassis where the rear gearbox would sit.

two outputs have a fixed length cvd joint , thats your above image, those two chrome tubes above that transferbox

brace the box from drooping, in a sandy you will have it hung inside the rear tail cage. 

Edited by Tamiyacowboy
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  • 2 weeks later...

Right....been doing a lot of thinking, mucking about, and general pondering as to how I will make the rear suspension....because bascially, if I can't make it how I want it, I might as well not bother, because it will just look like all the others....which is not what I wanted. I want a very low back shape and I want canted forward shocks.

 

So.... I have started looking at plan 'B'

 

Courtesy of E-Bay.... a 4" slab of T6 5/8" thick can be had..... which can then simply be cut to shape as per TC's sketch plan above. I can then bolt on the bearing carrier ....  It just becomes a simple swing arm. I could also opt for my original semi trailing arm layout, and make the arm from solid again. In the meantime...I am going to knock up some wooden patterns and see if the concept works before I order the alloy.

 

I know I still need to keep some tie-rods on the top of the axle to take the strain off the front pivots.

 

Plan C involves taking things one step further, and just making a block to carry the axle....then attaching a tie-rod to the front and side and making an L shaped assembly. This would bolt to the chassis via rod ends...one forward...one under the gearbox.

 

we will see though.

 

Every day, the temptation is to just make the cage a bolt on!

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found this while messing around. 

 

bottom of the page in link check the underchassis , the rear end

and the long fixed axle. 

 

http://www.damngeeky.com/2012/10/10/6043/mammoth-rewarron-worlds-biggest-rc-car-monster-trophy-truck-replica-with-a-powerful-engine.html

 

 

i do know there was some big scale 1/5th solid axles going around at one time made by a company called Yoto or the likes

Edited by Tamiyacowboy
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Right...time for an update. I was getting very bogged down with rear suspension setups, so I figured I needed to change tack. I was almost certainly heading way out of my depth, so I slammed on the brakes, and headed for safer ground. This is an area I can come back to later on when I am a bit more certain what I can achieve!

 

So....I went back to first principles.

 

I figured I could build something that made use of the rear chassis plate in it's entirety...tie in to the stock mounting points, and use the complete front assembly....but would ditch the pressed chassis in favour of tubes. Then I can play around with the upper tubing and get the look I want after I have done some testing to make sure my welding will hold up. The Baja is actually a total pain when it comes to cages....as I was desperately trying to avoid making it harder to work on than it already is. So many bits stick out or need to be removable....the more you think about it...the harder it becomes.

 

I have developed an even greater respect for the design Roofchopper/Tubedigger came up with whilst doing this!

 

Anyways.... progress so far.

 

1) Basic chassis rails

.Still need the cross bracing added and a few extra bits, but the layout is how I want it.

 

cage1_zpseaed74c6.jpg

 

2) Steering...

I want to use FG servo saver and servo setup, as I reckon it fits better with a rail, and requires far fewer mounting points. Just need a mount above and below, and the thing is sorted. Far less obtrusive and takes up far less space.

 

cage3_zps1cb4d9b4.jpg

 

3) Upper rails.

There will be an upper layer of rails, parallel to the lower, with cross braces for stiffness. This basically replicates the stock Baja chassis...but in tube not flat sheet. I plan on using a smaller tank, as I found with the Shorty I built, it's actually no problem at all to fill up every 20-25 minutes, as I tend to take a break then anyway. I don;t think I have ever run a full tank dry without a pause.

 

cage4_zpse51cc130.jpg

 

But anyway....

 

The front kickup will benefit from the IRC under brace, which I will add the extra mounts for. The rollcage area will start a little forward of the midpoint of the steelwork, so I can tuck the servo underneath. The radio box will also go under there, and if the gods smile....the fuel tank too. I plan on making a dashboard with some little toggle switches for the battery on/off and the manual killswitch. But that's not a priority.

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