drf

Nice to see a large scale forum added.

Since this is the place to put my post, here it is.

I am deisgning a 1.5 scale monster truck. I have seen a lot of other 1/8 ones and I believe making it really big will be a he11 of a fun. As I was thinking about it today (when I was in the bathroom) I think the best way to go is tube spaceframe chassis.It is the most difficult to work with but on the other hand has superior strengh characteristics to other designs. My first problem is to decide the power plant.
I was thinking of a 2.18 (36cc) Aero engine with a custom made heatsink or maybe water cooling as the truck will be big enough to accomodate something like that.

Any info-comments-suggestion welcome

Mel Francis

Ahh, as we all know, the best ideas happen on the 'throne'...hehe

That sounds like a custom challenge, for sure. What size steel tubing will you use for the frame, 1/2"? That would work out to 2.5" for the full size version of your truck, which sounds stout enough.

Although I mig-welded my 3/4" frame tubes, I might consider brazing next time around. It flows into the joints so much better, and damaged sections can be replaced by heating/melting an old joint.

drf

I dont really know what to use at this point. I will be having a big conversation with a friend of mine in a couple weeks time as he is a mechanical engineer and know more stuuf on metals than me. As I have it on my mind I think something like 1/4" but with a lot more connection than ussual. That way I can get the strengh and at the same time places to mount everything. I was also thinking about other metals. Magnesium was the first one I though. Altohugh more expensive and difficult to work with I may me a better idea as it has a better strengh/size/weight ratio. I will probably make a model in Autocad (pain in the *****) and simulate it as I have a proffesional software package for this (Abaqus) to see how strong it will be. It will take more time but on the other hand less money.(less "prototypes")

Welding was another thing that was troubling me. I have 3 options. I dont know the engish names for them but, 1. The one that uses acetylene and oxygen 2. The one that uses a gas(dont remember what) and a copper wire to make the joint or 3. The standard electric one (as the one used to weld ships) As the chassis will probably be aluminium I think I will use either 1 or 2.

My major problem now is the power plant. I have to decide what I will be using as it will affect the chassis.
Ideally I would like to use a four stroke engine as I could take advantage of the extra torque compared to a two stroke engine. On the other hand I can find a big enough four stroke engine.
I have seen small two stroke engines form chainsaws and other simila equipment that would probably suit me but since were not designed for racing or high power output wont be the "best". I have a 1.40 aero engine that I can play with if i finally decide to use an aero engine. Still thinking about it though.


By the way it has to be 4WD and as it seems in my mind belt driven although this will depend on how I will make the differentials.

It will definatelly take me quite a while to make it but I think it is worth it. Since my proffesion is electronics the finishing touch will be electronically controlled traction-suspension as well as braking bias to mention a few.

In a few words "it will be my big-small toy"

Mel Francis

Hmm, if you are working with aluminum, sounds like TIG welding would be the best, that would be your method #2.

For an engine, how about one of the opposed twin, four cycle engines sold for the large scale aircraft? Visit the other, aircraft side of this site and you should be able to find one with enough power.

You'll definitely need some Heavy Duty servos, probably the same ones I'm using. They're great, and fully waterproofed, with an o-ring seal between the case halves. I posted a closeup pic of the servo just this morning on the older giant scale thread we've been using, with a link to their site.

Funny your mention of the 'big small toy". I've been using the term 'small, big racer', myself!

drf

I have seen those engines. The problems I see is first price as are more expensive than the 2.18 I am thinking and secondly the difficulty to use a different head for air cooling. I was also thinking about this: http://216.239.37.104/translate_c?hl...8%26oe%3DUTF-8

It is definatelly the MOST difficult way to go but it would be next to nothing. I will get the plans and investigate it to see what is involved.

The servos are something on my mind but I havent decided what to do yet. The option are , either buy a heavy duty set, which is the easy way but quite expensive or make some. I could very easily use the electronics of a normal servo with some changes to drive any motor I like. Since I am looking at a heavy off-road vehicle I guess that the servo I will need will ahve to be VERY powerfull thus terribly expensive. I want to make as much as I can myself to tailor fit anything to my needs unstead of altering my needs to suit to equipment.

Mel Francis

Wow! The engine looks beautiful, but it looks expensive, too. But great if you can work it in, since water cooling would be the best.

My first attempt at H/D servos, involved 12v automotive window-regulator motors, with a positioning sensor attached. Looked like it was going to be quite strong and well-suited, until I discovered the VANTEC units.

I just went ahead and bought them, since I need to use components that were off the shelf for this application, if it becomes more popular.

drf

The egnine look superb and they also have plans for v8 ,v10 and v12. It is not very difficult or terribly expensive as long as one has a CNC. Unfortunatelly I dont. But I think that if I port everything to a language a CNC machine can understand there will be a company that will do it for a resonble amount of money.

The VANTEC units are excelent but far more expensive than I would be willing to pay. Their price is two of the engines I think to use for just one servo!!!(The engine is 225USD)
I think I will be using multipule servos joint together, at least in the beggining. I have found Supertec servos that are high torque and good value for money.
£19 for 0.28sec/60º - 13kg.cm BB servo sounds like a very good deal. My father uses supertec servos in his large scale planes and does not have any problem. I think two of these would turn the steering ok. Use another four (maybe not that strong) for braking and another normal for throttle.

Searching on the internet I also found some very strong stepping motors that are used to replace industrial servos. The price is similar to the VANTEC but those are faster. It is more difficult to interface them,both mechanically and electrically.

Since you mentioned he window regulator motors. A very nice motor to use would be one used in 1:1 cars for the windscreen wipers. It is really strong and really cheap as well. The problem still relies on interfacing and position control. Hmmm it sounds like a very good trick to do if the electronics of a normal servo is used. I have to look into it.....


Thanx for the support and comments, I hope more people will get around in the large scale forum.......

Lost Down Under

GWS have a new 1/4 - 1/3 scale servo on the market. They are well priced & at 6V have 28kg of torque. I think the part # is GWS 666.

Have you thought about titanium for the frame? Strong, light, can be tig welded & if you get really excited, you can annodise it.

Sounds like a great project.
Good luck.

Paul.

drf

I cant find any info on the internet on that particular servo.

I have though of several metals but I havent taken a desicion yet. I have to consult my mechanically orientated friends knowledge before hand(They spend three years in University playing with that stuff-they should know more than me)
I havent seen anything big using titanimum. It sounds good but probably make my budget hit rocket sky prices and it is difficult to find as well. Still looking into it though.
I dont think I will be anodising anything on it. I dont really like the color (it reminds me of crazy japanese tune-to-hell cars with huge rear wings etc) I prefer using normal colors sprayed. Either way everything will be protected by either thin aluminium or lexan so nothing will be in clear view.

I hope I will manage to start and finish it.Usually when I am back home work just piles up not leaving me time to do anything....

Mel Francis

If you need a visual on the possible hookup of an existing auto windshield wiper motor to a regular servo, perhaps this will work.

The regular light duty servo was stripped of it's gearing and the positioner rod hooked between it's arm and the arm on the large motor.

The two small red and blue wires are connected to the two different sides of the power connection to the internal motor, which then went to external relays and into the large red and yellow wires to the large motor.

It worked, but was a real lash-up, and luckily for my project, I found the larger 105 Tonegawa Seiko servo online and went with that. Remember, VANTEC also sells their 050 servo for under $200, which is water-sealed and puts out 690 oz/in at stall and 8.4 volts.

mbba2002

My Feedback: (10)

I have already designed and built a 1/5 monster truck. I entirely built it out of 6061 aluminum. I used a 22cc echo motor. The truck has 4 wheel drive with 4 wheel steering. Weighs in at 55lbs. the truck needs to be light and to put stress on the steering.I use the tone servos.(900 OZ) Anything less dose'nt have enough power.I tried every other 1/4 scale servo and they did'nt work. You need a motor with at least 2 hp or more. If not you won't get good speed and power. If you are trying to build on a budget(cheap) forget it. Price won'nt compare to a 1/8 scale car or come close. Chain drive is the cheapest type of drive line there is and the strongest for the price.

drf

Do you have any pics of it?It would be nice to see how big it looks just to get an idea instead of working with scales.
Did your four wheel streering works on each individual wheel or is the chassis trunable in the middle?
The motor I am thinking is a 2.18 aero engine (36cc) and it is recomended to be run at 5-10% nitro so I guess it give something close to 3hp. I believe it is good for the beggining and if I need more power I will put something bigger into it (a big chainsaw motor?)
In the beggining I had not tought of the servo problem. To be honest I would never pay the price the huge servo cost. It is not the money itself but I think that those are WAY too overpriced. I'd rather make one myself with a custom pcb and gears for a standard 12 volts motor.
Chain is a nice to use but I need something more presice with less noise. Now I am about 95% cetrain that everything will be belt driven. I have though a good way of powering both differentials from the center one easily. Still looking into it though.
I dont intend to make it on a budget but on the other hand I dont want it to cost like a 1:1 car.
By the way how did you make the differentials? I want to make mine sealed with oil to be able to adjust them but it is giving me some hardtime trying to figure out how to make them.

Glad to see we are increasing in numbers in the giant scale forum.
Post some pics if you have,I bet it is awesome!!!

mbba2002

My Feedback: (10)

Hope you got the pics. I have the steering on all 4 corners. I use a quick change rear end( skellenger). You can build a rear end simular it if you want? Zenoha has a 3hp motor that runs on pump gas( g230). I have used chain drive for 7 yrs and have had no problems (25 pitch).

Mel Francis

Here's a photo of New Era Models research vehicle.

Six-wheel drive, using their own differential asemblies from their quarter scale line.

Here's their URL, set for the page that describes this truck: http://www.neweramodels.com/cgi-bin/...pghilusgmuweon

volsstd

G-sus. for 19.500 $$$$ you can build your own freakin one.


Ben

nodolarsnosense

damn $$$$$ is it a result of the american space program, ie the 6 wheeled mars walker, cos although its very good that is incredibly expensive

unioncondo

Hello

I'm new to this board. I'm researching scratchbuilding 1/4, 1/6th and 1/8th sprint car and midget models. These will be static, not radio controlled. I see you guys use quick change rear ends in some of your trucks. I'm desperatly trying to find a source for QC's and would appreciate any info you can give me. I'm also looking for suspension parts. By the way, all I need is the QC center section and tubes, I don't need the guts.

Any suggestions/information appreciated. Please reply here or to <[email protected]>

Thanks very much!

Rick

fritolay

unioncondo - They race smaller scale sprint cars, some with winged, in NY and PA. Kranzels Hobbies races them on an indoor oval track. Reason I point that out is that Kranzels has a custom kit they sell that is a winged sprint car and I think it's called the terminator or something based off that. (I still have mine but have since moved from the area)

You could take a look at these to see how you would maybe go about building a larger scale one.

By the way, I think that would be fun too, so let me know if you find out more information.

crxman

Mine is machined from dual 1/4" 7075 aluminum plates, They are very strong, and durable. Not as much for the looks, but from a more poerformance aspect they work excellent. The plates are both 40" long, have many 1/2" solid aluminum crossmembers, and a 150cc 14.8 hp engine. Total I spent around 1000 dollars. Aluminum is a very strong metal when used correctly.