Airtech claw rig. Couple of changes

[Grosse Kind]

Evening kiddies. Got bored a little while back and chucked a few more alterations on 8868. Couple of pics and two short videos should be self explanatory of the bulk of it.

First off, a question. I've tried to measure it and i'm getting a ratio for the half width bush groove vs the 6 hole pulley of 3 1/2 to one, and for the large two holed older steering wheel pulley of 5 1/4 to one. Any one got any definitive figures on these perhaps? Thanks in advance.

I have added a simple 2 ratio set of gears at the front with a 12/20 or 16/16 combo which when used with the two variable pulley setups i put in place of 1:1 and it seems 3.5:1 make ratios of crankshaft to rear wheel of 3.33:1, 2:1, and an overdrive of 0.95 or 0.57:1 available. No need for any gearbox of course but thought why not. Theres a triangle liftarm as a floating brace to help stop gearshaft spread as i have no three full hole half width liftarm to go there. The 12/20 is reversed from my last build of the set as now instead of my wanting a less loaded drivetrain vs the original, the other pulley setups meant i could magnify the gearing this time round and it handles it fine. Popping the belt over from the big-small combo to the all small with two idler setup and back is a little fiddly with everything in situ but i've done it a few times.

2.77 and 1.67:1 are possible according to a rendering i did in LDD with a 20 driving a 24 tooth gear pair in place of the belt but the twenty in practice skims against the axle beneath it that drives the pinion on the steering rack. I may pare down the cross on one of my damaged axles to give clearance one of these days but for now i'm comfy with the belt. The six hole belt wheel fouls said axle more thoroughly so the highly underdriven crank ratios of the original aren't possible without further alterations that i don't deem acceptable: technic sets i try to only utilise or add to the original frame which rules out external dimension, wheelbase, height, and length changes. Suspension height/travel ,and wheel track i'm content to screw with but i like what once was, to stay looking like once was.

I've obviated the belt drive to the compressor taking the drive ratio of 5.25:1 down to a faster 5:1 and triple the stroke on the compressor is via an 8 tooth onto a 40 using a 36 tooth as the other side flywheel which as luck would have it clears the passenger seat. It's handling it fine and the new pivot was well within range of the extension of the standard length clear pressure tube. Pump seems a tad more efficient now and even with half flat batteries isn't unduly loading up/stalling the electrics and i'm not gonna bugger around tracking down airtanks, they seem superfluous.

As the steering gears moved back to accomodate the motor now taking drive from behind, the two sixteens didn't fit above the axle that keeps the tube manifolding that runs to the switches out of harms way. A half bush is now on the back end of said axle and the full bush at the front is shifted back a stud but could be eliminated entirely. I'm just lazy, and it's there if i want to return it to standard. The room its moving leaves gives space for a 12/20 combo that overdrives the hand of god a little but the 14 tooth bevels are handling it with no stress and its still playable.

Theres all the driveshaft and diff bracing still in place from last time i delved it so no real need to re-show that i figure.

Not totally happy with the fan now sitting external which may see me just leave it off but dealing with guilt fine for now. Grey grille/radiator shouldn't have an engine driven fan feeding through it and not finalized on the shape of grille still but it got a few of the bits i needed to move to alter the front engine mounting retained on the model so i can, once again, find them if i want to build it back to stock.

Yes i've made an ugly duckling out of a beautiful swan but let me know what you think. Certainly happier that the pneumatics work better and the somewhat "komische vögel" use of a V6 in an application that should generally be inline or a bent eight is dealt with.

(First two thumbnails are links to the videos)

[NevynPA]

That's pretty awesome! What's the pulley wheel with the belt on it for back in the yellow section? I've thought about trying to increase pump performance, but hadn't thought beyond switching to a new pump with a different stroke. I just added a tee, a manual pump, and a pair of white air tanks to replace the brick-built fuel tanks on each side.

[Grosse Kind]

G'day Nev. Thanks for the compliment but its a bit over the top. I just dabble with this shit when the mood takes me.Pulley and belt are on one side, crankshaft ends and toothed half width bush (pulley on electric motor) are on the other as these are what was replaced to do the compressor drive/stroke alteration and are there like the 1x2 45° slope bits in the grille, so they stay somewhere on the vehicle to allow a swap back to dead stock without hunting for the supplicated pieces:

Do this on any of my changed from stock models. Like the gearbox ratio change on 8860 and 8880's suspension height and crankshaft phasing pieces as who knows who will later end up with my collection and they may be (heaven forbid of course!) purists who insist on box stock. I'll be gone so it won't of course matter but makes me feel better about it. A habit born of having to hunt for and pay through the nose to get the missing trinketry that completes a restoration on bikes/cars i've found or inherited over the years.

Exceptions being where the removed items are huge and proclude easy onboard secreting, then they stay separate and in one piece. Narrowing the track on an 8865 is so far the only time i've resorted to that as grey 16 beams were a bit bulky to worry about incorporating elsewhere on it:

Not saying it'll be everyones cup of tea, but by all means try the compressor changes, the benefit i reaped seemed worthwhile.,

Edited June 1, 2016 by Grosse Kind

[1974]

My 8868 uses two pumps, powered by a 71427c01 9V motor (much more powerfull) through two pneumatic tanks (instead of the fake ones). Works very well and can power the pneumatic outriggers also

Cheers,

Ole

[Grosse Kind]

With the two pump method Ole, you got em sequential or big bang disposition (close firing order, like a 360 degree paralell twin 2 stroke, or an IFA BK350 boxer) ? Does ones effort diminish the others if they are phased at say 180° or if together the combined load up the motor? Whats the stroke you are running? Sorta tempted to look under my unimog and see if it can be ramped up a bit too as the short push just feels like wasted potential. Kinda as if making 10 tiny taps to hammer a nail when twoxgood ones would see it home. That said, the two twentyfour toothers on the drive out of 8110's motor are getting tooth thin already, powdery crap all over the nearby beams so perhaps more load on its not a grand idea.

[1974]

GK, yes they're 180 degress out of phase. That cancels a lot vibrations. Each pump goes to pneumatic tank which is then combined to be used for the switches. I'm using old pumps (5.5L)

Buy a LEGO pneumatic pressure gauge and you always know if iyou're doing right

[Grosse Kind]

Each tank would have its own check valve on the inlet so that'd be good, and the rest of the manifold can then act as a pulse cushion.

Are they both reciprocated as per original by a half stud offset crank? You gone belt or gear propulsion?

Any reason to duplicate pumps other than its a pushme-pullyou arrangement? Seems everyone is adding driven and manual pumps willy nilly, even the standard pump setups reaction times aren't all that bad when you consider them in scale to an actual HIAB or the hydraulics on a tractor where even an arseload of pressure and flow is slow reacting with high displacement rams with wide-as pistons that are needed so they can actually lift stuff. I know this is air not incompressible fluid and all, but how fast do you really need them to be and what sorta giant objects are you lifting with them?

I reckon what CP5670 wrote one day would be right though i've never owned one: "an airtankxwill help keep the pressure up but makes precise control harder in practice".

Is there a relief valve or pressure regulator made to keep things at a constant if you've got the pump working well enough to never not be pressure dropping whilst in use?