Project Lego Technic

Not your average Savage Hop ups. These are highly modified, with some home-made parts.

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Liv4RC
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Re: Project Lego Technic

Post by Liv4RC » Mon May 20, 2013 4:51 pm

Length of Losi body is 21-1/4" overall and is on a truck with wheel base of 15-3/4".  It is an average of 1mm thick.  It has held up better than any other body I have tried on my Savage basher.  That says a lot when it flips and it takes 18 pounds of beating from my Savage!
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Post by johny723 » Mon May 20, 2013 4:52 pm

how durable are these bodies?

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Post by Liv4RC » Mon May 20, 2013 5:04 pm

I guess it depends how you drive (or crash). I usually get a year out of one body.  I jump my truck off 3 to 4 foot jumps, sending the truck maybe 10 feet in the air.  It takes a lot of crashes from this size of jump, but I've seen guys launch their trucks 50+ feet and crash.  Not sure how it would hold up to that.  Can only go by my experience, but I am running them on my Savage and Losi XXL that can all reach over 60 mph+ while running 6s lipos.  I've had crashes where wheels were ripped off and drive lines were shattered, and the body was just scratched.
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Post by johny723 » Mon May 20, 2013 6:19 pm

Thanks !

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Post by johny723 » Fri May 31, 2013 6:24 pm

the time has come for an update. Sorry for a slow progress and occasional updates, university was consuming and taking all my time. Not just the free time, the whole time literally! I have graduated recently, so I have much more time for anything I can even imagine to do :D Let me introduce myself as johny723 M.D.  :D
fortunately there are more important things than medicine, e.g. my project !
I think I managed to build the ultimate monster truck machine ever known to mankind :D I decided not to cut corners anywhere and use the cheapest, but still first rate quality parts, no cheap rubbish, which also slowed the build down a bit( a LOT :D ).

I decided to name all the features as a list in one place, although they have been already mentioned and posted:

a huge bumper and a corresponding skidplate from hobbyking baja 5t , I hope no shock shafts will ever need replacing or bending back straight, because even 5mm thick revo pushrods I use in my LST shocks can bend if they take a hit!
Image
Image
I also cut a 1mm steel sheetmetal to protect the plastic parts from rocks and other obstacles my truck will make its way through!
Image
Image

5mm revo pushrods as shafts in lst shocks
Image
some plastic rod ends + a turnbuckle or a screw of the right length to keep my shock towers straight and protect them from bending caused by lst shocks Image

front and rear sway bars: 3mm thick music wire, bent and cut to a desired shape and length + some plastic stuff from turnbuckles and savage servo linkages. I drilled 2,5mm holes into rpm arms for mounting screws Image
how they are held in a bulkhead with 2 M3 screws amd washers Image
you can also notice I use 2 bulkhead braces instead of one. I heard of people ripping and tearing their bulkheads apart with rpm arms, so I added an extra brace to keep the bulks in on piece. Some alza or bashcat bulkhead braces would be defintiely stronger, but hey, this is a budget build! :D

When talking about the bulkheads, they contain a set of cen gst 7,7 differentials. These need to be shimmed quite a lot, both the pinion and the diff itself, but I took my time and patiently shimmed them to as little play between the pinion and the ring gear as possible, and they have not let me down for 2 years! Image
Image
they show some minor wear, but that is unavoidable with the power of my CC 1520 motor
A good side of them are 3mm thick pins in for the diff outdrives, 8x16x5mm bearings they use on both ends, strong bevel gears and beefy teeth, their module is similar or the same as the module of HPI bulletproof diffs
The only downside is the diff case, its made of aluminum, but it is kinda soft, but I think 1 stripped thread in 2 years is acceptable. They use a 3-piece design, so I just swapped the sides and the hole with stripped thread is on the side opposite to the ring gear. Not ideal, but it has worked flawlessly.

The cen diffs needed some special dogbones to pair with, so I picked LST 2 Constant Velocity Driveshafts, that are stronger than HPI dogbones and also longer!
Image
LST ones and savage x older style dogbones between them for comparison
I also wanted some stronger hubs, so bought a set of cen gst 7,7 hubs and carriers. They are stronger than stock savage hubs and were so cheap back in day  I could not resist buying them :D
the thickness of the hpi savage on the left vs the cen gst on the right
Image
that solution had some teething issues cause by 10x19x7 bearings in the cen hubs. but I solved them by using narrower 10x19x5 mm ones. The cheapest I found were from china, but they are still working flawlessly! The bearings these cen trucks use in hubs are stronger than savage bearings as you can see here Image and the distance between the bearings in the cen hubs is greater than in the savage hubs
The smarter of you are asking a question right now, and the question is how I made lst cvds with axles of 8mm in diameter work woth 10x19x5 bearings! The answer is simple, I used a metal tube with inner diameter of 8mm and outer diameter of 10 mm and I put it on the LST axles as a spacer between the bearing and the axle part of the cvds
Image
so using lst 2 cvds + gst hubs killed 3 birds with one stone! Stronger hubs, stronger bearings, stronger CVDs and a wider stance on top of that!
I also found that cen hubs work even with LST hub carrier, not solely with the cen gst, and I tried that on my truck. I used the cen gst carriers as front and lst 2 carriers as rear ones
the LST carrier Image
Image
the cen gst carrier
Image
they both work with cen hubs

Upper arms needed some length increment too. I use upper arms from savage x ss line of trucks because they are adjustable. All that was required to make them longer was a longer turnbuckle. I could not find a M5 turnbuckle of the right length at a good price(= cheap as chips, dirty cheap), so I used an ordinary M5 screw 50mm long to act as a turnbuckle. here it is with a nut I glued with a red threadlock to help with adjustments Image

Turnbuckles from bulkheads to hubs needed some length too. I used either 80mm m4 turbuckles with stock savage plastic rod ends or revo pushrods. I prefer 80mm turnbuckles, because they offer more precise adjustability and the plastic rod ends are more flexible than those on revo pushroads, But both of them have beed succesfully tested and both of them work, it is just my personal preference.

That is all for now, I am tired of typing....

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Post by FluxNZ » Sat Jun 01, 2013 2:43 am

Very impressive Johny 8)

I'm Liking the LST Hub carrier + GST Hub setup using the LST CVD's.
Also it looks like the LST Hub carriers have some castor built into them as well? What's the steering lock like with this setup?


It looks like a simple bolt on upgrade and plus it's a strong setup which is something that I'll be looking into for my big rig. All I would have to do is change the dif output cups to the Vorza cups so the LST CVD's work.

Need some more photos of your truck with the wheels on (from different angles), video would be nice too :wink:
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Post by LLkoolskillet » Sat Jun 01, 2013 6:57 am

I thinks it's cool to see all the different pieces work together to create a stronger setup.
[img]http://i1105.photobucket.com/albums/h358/LLkoolskillet2/skillet1.jpg[/img]

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Post by johny723 » Sat Jun 01, 2013 9:20 am

the weather is horrible, I dont want to drown my HK 150 esc that has been working for 2 years in some stupid puddle :D a video will come later.
cen gst diffs work with lst cvds, original gst cvds have the same size of ball ends, so you dont have to change anything.
But if you want to use these parts on your huge truck, I would recommend you looking at J1A1H's lst hub setup, he uses 3 bearings in each hub, which is a lot stronger system than my 2 bearing gst hub setup modules.php?name=Forums&file=viewtopic&t=91444

and I dont use the lst carriers on the front, just on the rear, but tried mounting them on the front and the steering looks like this
Image
Image
it adds some nice caster, I might try them on the front as well, time will tell

the list of mods of my truck continues :
It is built on an ofna lx 1 buggy chassis + a savage bulkhead plate mounted together
Image
with savage flux composite bulkheads on both ends, a hyper 7 center diff and a LST 2 CVD as a rear center cvd and a front savage center dogbone as a front center dogbone
Image
Needless to say, I had to drill new holes for savage bulkheads into the chassis, they required high precision and it was the crucial part of the whole build. Imperfections would cause both ends have their own track and the whole truck would be a disaster to drive. the braces are made of alu tubes and long bolts with plastic turnbuckle ends. Their thickness is 8mm, they are not hollow, so they should handle some abuse. I do not use cen gst turnbuckles as chassis braces, they did not have the right length
ImageImage
the brownish plates mounted on bulkheads in place where tvps attach are made of pcb board material, its basically fibreglass. Easy to work with, light and strong enough for structural components.

hyper 7 diff mount is mounted on 5mm standoffs to gain enough clearance for a 52t spur gear
Image
you can also see a heavy duty servo saver spring, a must for powerful servos and big wheels!
the lst 2 cvd needed some serious modding to fit.
I used the whole cvd, so I had to found a solution how to drill it right through the center and how to put a bearing on the axle part of it
I came up with this - Image an old center diff mount from Hobbyking trooper.
The problem I had to overcome was the agle of the rear part of the ofna lx chassis, which means the CVD comes out of the diff pinion outdrive at an angle. I solved this by putting small washer between pieces of the diff mount, which gives me some space for angled position of the bearing, as it is not vertical, so the bearing has a mm of vertical play not to move, but to find its position.  
Image you can see, after a closer inspection, that the rear bulkhead is angled forward.

drilling a hole through that cvd was a nightmare, losi use very hard steel
However, I managed to drill it. The key was to glue a savage or any other diff pinion cup on the cvd Image put it into vice and drill the hole through openings for the dogbone pins. Not quite a CNC level of machining quality, but still precise enough. the red spot is where I driller the hole
Image

the servo mount:
the mount is made of 4 posts, each of them comprises a M4 screw in an alu tube with ID 4mm and OD 5mm. When tightened with a nut, it creates a strong platform for the servo itself.
Image
the servo itself is attached to a piece of fibreglass, that is mounted to the these 4 posts.
Image
Note there are another 4 nubs tightening the servo plate to these posts
Image
lower nuts hold the posts ( = the alu tubes and screws) straight and upper nylon nuts hold the servo plate with the servo tightened to these posts. This solution enables quick servo maintenance, as all I have to do to get the servo out of the truck is unscrew the 4 nylon nuts and it is in out, with the posts still in their places, so I can mount it back in no time!
The linkage is made from revo pushrod ends and a piece of M4 screw. Solid and tough.

The motor:
I use a mighty cc 1520 kv 1600 brushless motor. The mount for this beast is a 4mm thick alu angle attached to the diff and the chassis. As I did not have access to a thicker alu angle, and since I could not find a motor mount from hyper 7 or 8 conversion at a good price,I had to stick with this one.
Image
Image
To prevent it from bending and messing up the gear mesh I made a support under a back part of the motor. I unfortunately dont have it in photos, thats a pity, but trust me it is there :D You can see a zip tie around the motor, it attaches the motor to the support beneath it :D The 1520 does not  move a tiny bit. I will surely change this motor mount system to a proper motor mount from the hyper 7 or 8 conversion kit, but I am tight on budget now and it is hard to find someone selling just the mount without the rest of the kit...

the battery tray:
I hacked up my own battery tray from various plastic cases I bought in electro store. They are meant for homemade electronic devices, and are pretty strong. The battery tray is pretty big, I build it large enough to accommodate batteries of this size and even bigger - Zippy 8000 mAh 30C
Image
Image
the battery is secured in place with 2 velcro tapes. It is big, so I expect pretty long runtimes.

All of the heavy components, motor, battery, esc, are mounted as low as possible to gain as low center of gravity as possibl:D . I hope the truck will be literally planted to the ground!

To stiffen the chassis up a bit I also decided to use an upper deck plate that goes from the front to the rear bulkhead. It allows some chassis flex, but just to a limited extent. It is the brownish plate you see in this photo. As usual, I used my trusty PCB fibreglass. 1,5mm thick, but the chassis is way  stronger.
Image
Image
When it flexes, it leans toward the center diff mount and another metal post in the rear part of the vehicle that stop its flexing, so it wont flex too much.

Image

and to deserve the Lego Technic name, I found a propeller in my old lego technic kit :D that I glued to the front center dogbone. I dont like dogbone at angles, the heat hup quickly, and although this is not the case like losi 8ight trucks, I put it there just for sure. When the car moves forward, the propeller acts as a little fan that cools the front diff cup
Image
Image

if you need any photos or info just let me know. Sorry for accidental mistakes, I have not typed so much english text in my entire life and I am not a native speaker :D

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Post by FluxNZ » Sat Jun 01, 2013 5:02 pm

You show great skill making thing's work with what you have and sharing this info with us will help others with their builds.
Your  english text is fine Johny:-)

I'll still give this setup a go because it's still a stronger setup than I have now (bearings and all) plus I don't need to extend the bulkhead braces like other mods do to run the Lst Cvds. The only thing now is a proper 24mm hex to suit the axles. I see there are some still around for the old 5T Savage but are on European sites which are hard to order from.
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Post by johny723 » Sun Jun 02, 2013 4:59 pm

It is a simple equation. The lower budget and equipment you have, the smarter and more ingenious you become. It is a natural selection :D But I think I would be building trucks like this even if I were a millionaire, I just can not morally justify huge amounts of money dumping into big boys toys. Cant wait to become a millionaire to find out  8)

ebay.com has some 24mm hubs for you
http://www.ebay.com/itm/HPI-Racing-Sava ... 87f5f#shId

http://www.ebay.com/itm/BNIB-ALUMINUM-W ... 338202e940

first tests showed that the truck became planted to the track! there are almost no wheelies! And if there are some, they are "deliberate" wheelies "wheelied" intentionally! The truck in its old shape would wheelie pretty much anytime I pulled the throttle, whereas now I have to jam the throttle to get some wheelies. But I must admit that my batteries are getting on a bit and are behind their prime, so even freshly charged I can not tell how it changed in comparison to the past construction as I did not run the truck from december to may and the lipos started to fade away slightly... more school than life... a very bad period of life... Sounds like a good reason to buy some new batteries with a fresh punch! The acceleration is much better though.
I had some teething issues, just a few minor bugs that required an easy fix, but you can not avoid some problems if you make parts from 8 or 11 manufacturers work together. Good news is they were not serious, only few loose screws and cups. I fixed them with a red threadlock just to make sure they stay fixed as they were quite important screws from pinions and diff cups... What can be worse than a tiny screw ruining the entire fun?! Broken chassis, blown tires, shredded diffs and busted arms etc are an acceptable reason for end of bashing, but one or two screws that got loose can make me really angry  :!:

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Post by FluxNZ » Sun Jun 02, 2013 5:14 pm

Yup you can't get away from minor bugs in the project :)

Will be good to see the truck running in some videos later.

Thanks for the links.
The 24mm hexs I'm after are the old 5T nitro ones which will bolt onto the LST axles no problem (5T had a buggy type axle). I have found some in the UK so I'll see if they arrive because most places are out of stock due to them being no longer available.

Cheers for the update.
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Post by johny723 » Wed Jun 05, 2013 5:43 pm

A trophy truggy body shell has arrived. The only downside - it is a couple of cm shorter than it should be for a truck this size... I will buy something longer next time, i.e. losi LST 2 or so. But it could be much worse, in fact it does not look that ugly either...

a real problem is my radio... I managed to break the whole antenna off the transmitter    so the range and interference will be a problem now... I am afraid all the test runs within next few weeks will have to be postponed until I buy something new.I have some 27 and 40 mHz radios, but I do not risk running a big fast brushless truck in the city within all possible kinds of interference with any of them. The truck could be fixed in no time, broken leg of a child not. I know that first fluxes hp were sold with with a 27mHz tx/rx, but they used MMMs, which is interference friendly, but that is not the case of my HK 150a esc...
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Post by johny723 » Fri Jun 07, 2013 3:05 pm

I could not resist running the project I was working on for so long, so I tried the transmitter and it works! I started at a snail pace to see how it runs after I made sure there were no people or animals or anything else that would come into my way to get hit, but after I realised it the truck is as obedient as it used to be, I jammed the throttle for some WOT speed runs. I tried it in the city, so lots of interference from all directions, wifi, cellphones, cars etc, and I still got a decent distance between me and the car without a SINGLE glitch! These things are tough, they have a nice range even with a 1cm long antenna!!!
On top of that I found my HK150 esc has a fully working fail safe, so car stopped immediately without going mad on any occasion the signal was lost! The chinesse have surprised me once again!

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Post by FluxNZ » Sat Jun 08, 2013 3:52 am

Good that's it's running for you  8)

Let us know when you have a video :wink:
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Post by FluxNZ » Sun Jun 09, 2013 11:54 pm

Hi Johny,

Did you have to alter the hub carriers much to fit them. I just got the Gen ones here in the mail and they are a very firm fit? They spread the A arm mount point a bit due to them being a bit wider than the spacing of the stock hub carrier? What are the Losi LST2 one like for fit?

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Post by johny723 » Mon Jun 10, 2013 7:18 am

yes, some minor modifications were required. these little mods are not mentioned, because there were just too many of them to list, so I skipped them :D
You have an advantage that you dont have to figure them out on your own :D

I had to file like 1mm or so from these places to make gst hubs fit
Image
and the gst hubs use a 3mm screw for mounting, not a 4mm one like the savage hubs, so I cut a copper tube with ID 3mm and OD 4mm and I pushed it
into holes of savage arms where c-hub screw goes through, so I could use a long M3 bolt to mount the gst
you can see it as a small shiny line in the hole for the mounting screw- that is the copper tube
Image

You can also see aluminum spacers to prevent the gst hubs from deforming.
Image


The lst hubs are even wider than the gst hubs, so I had to file these small areas that were protruding
Image


if you really use the gst hubs, make sure to secure inner bearings in their position, because they had a slight tendency to fall out of their position and fail. Nothing serious, I had only one failure of a 10x19x5 bearing. Even Cen secure them in place with some kind of glue. I personally do not like any glue around my bearings, so I cut stripes from a beer can, 1,5 - 2 cm long and 5 - 7mm wide and put the in place where bearings were to go between the hub and the bearing, and the bearings had to be pressed with some force, which was enough to secure them in the right positon.

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Post by FluxNZ » Mon Jun 10, 2013 12:12 pm

Thanks for the info Johny. I'll use the LST hub carriers first and I do remember the other member who used these had to file a bit off those places to make them fit.
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Post by johny723 » Mon Jun 10, 2013 1:12 pm

you will also need some thin metal foil or tube to put around screws mountig gst hubs to lst carriers. There is some play between the screw and the carrier. That is a bad side of putting together parts from various manufacturers and models- they work in principle, but always have bugs and need further "refinements" to work precisely.

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Post by FluxNZ » Mon Jun 10, 2013 4:01 pm

Yeah I thought there would be some tweaking to be done but I'll nut it out some how :wink:
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Post by johny723 » Tue Jun 11, 2013 4:33 pm

I also recommend that you cut a protruding portion of the hub where the turnbuckle is mounted to like this
Image
to eliminate the bumpsteer which will be an issue unless you do something about it.

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