Cat 777 questions on build

[Cooper]

Hey guys I have been wanting to build an adt but I think I would benifit more from an off highway dumper. I'm thinking about building something around a 777. Not the big boy 797 and not a smaller one. Some questions I have are looking for the tire size. 1:14 scale build. Where to purchase something for that scale and style. And the other big question I have is drivetrain. I was thinking about using two gear head motors for an axle/drive system. I don't know if any regular axles would be beefy enough to handle the weight and power needed. That was why I was thinking of gear head motors, one for each side built into axle like fumotec uses for the adt. And I have no idea what rpm range would be best suited. 12 volt system I assume I would be using, 100-150 range? Any suggestions would be appreciated. And I have noticed these trucks use two stage cylinders or dump hoist. That may be a challenge. I know the sand master dump uses a screwdriver, but I would really like to keep with cylinders. If any of you have had any of the multi stage hydraulic cylinders apart and a pic of ends of cylinders that would be appreciated too!!! This is in the concept stage and I've kind of decided a off highway haul truck would be easier to make and better suited for the construction company. I think the top of body is around 12" high, that would still allow me to have the excavator load it. Thanks for any suggestions and or input!!!

[9W Monighan]

I think you need to make the driveline like the 1:1 . Build the rear end from scratch with planetaries and have it be able to lock for the steep grades and make it very heavy so you have plenty of traction empty. Triple sevens are one of my favorite rigid frame trucks. I was up around Clearfield ,PA last week and stopped by a friends strip mine to take a look at his B-E 380W he has parked. ( He can't find an operator to run it. Keeps bugging me to come up on weekends and move some dirt )
Anyway, There was a couple 777's doing the job of the dragline hauling rock out of the pit and stock piling it on a huge spoil pile at least 150' high. What a site seeing them back out on the narrow pile about 200yds.

[Cooper]

I know these are expensive, but would only need one. I wonder if they would be able to haul 20#s of dirt in the bed. I just guessing but 15 pounds , does that sound correct for 1:14 payload? Without looking at conversion?
http://www.afv-model.com/4711shop/pr...oducts_id=3727
I've never attempted making an axle let alone the part that locks. I'm thinking to start with tires, then build around them. As that's one thing I know I'm not going to scratch build. I started messing with planetary gears I pulled from the "upgrade" kit for the 4200 excavator. Plenty of reduction.

[Cooper]

And sorry we couldn't get together the other day, have some old friends in the clear feild, snowshoe, areas. Haven't been up that way in a while.

[9W Monighan]

Those look like some nice axles. I would like to dissect one of those.

I forgot to add, with the standard drive line you could put a high low gearbox in there .

[Cooper]

They are the axles used in permacons articulated dumper. I was thinking with the planetary gear on end of axles that would lessen the abuse. I just hate to think of spending the coin of them to find out they aren't up to it!! And like you said having a two speed tranny plus ability to lock the diff. And the best I've found for tires is 2.2 size, they are mil-spec from rc4wd. 5.19", scale size would be closer to 6" but they might have to do.

[bigford]

out of stock but how about these?
http://imgout.ph.126.net/39548003/SIZE.jpg
http://www.rcbrmin.com/rubber-tires-...der-p-735.html

[Reebs]

http://youtu.be/1Qvx9eOP_QQ

http://www.northerntool.com/shop/too...7724_200037724

[modelman]

Cooper-I'm sure you have found this out by now but tires are the hard part on this type of build. That is why I made my tires when I built this model. My scale was a lot smaller but I think I got the dimensions pretty close on everything. According to my numbers the full size tires were 107-112" tall X 28-30" wide. When I look at a model side view I find several things that my eyes go to immediately to define the model and the tires are the first thing on this truck. That is why I decided to make the tires first and if it worked I would build the truck. To me exact scale was not possible and I am not sure what your feelings are on this. But exact scale will be really hard unless you have one close by that you can measure. The way these trucks are designed (all payload) there is very little room for anything else but I am sure you will figure all this out. Looking forward to watching this. Good Luck

[Exclusive RC]

Hey Coop, if you decide to take on this job, it will be AWESOME!!!!! But I think you may have your measurements a tad bit off... I did an exuberant amount of research on this truck because before I built the 773G I was going to build the 777, ( I think i mentioned this to you at cabin fever, not sure) The main reason I did not go with this build was because of the tire size.... There was no way I was going to be able to design and 3d print a tire mold and produce rubber tires in 1/14 scale within the month it took me to build the 773G. So I basically looked at the biggest most realistic, tire I could find and build the model from CAT that matched the tires, thats when I came across the 2.2 rc4wd Milspec tires that matched the real life tire size on the 773G.... The 777 on the other had is a whole diff beast... there are 4 types, (dump bed types) Dual Slope, X Body, Coal Body 1 and Coal Body 2 all different heights at the front canopy, shortest being the dual slope at 17' or 5200mm and tallest being both coal bodies at 19' or 5840mm, so assuming you would go with the shortest style bed at the canopy in 14th scale you would be looking at 14.57" or 371.42mm tall which would make it a little over 13" tall at the bed side. Length wise again, depending on the body style would be anywhere from 29" to 31.28" long from bumper to bed end. Last but not least, the 777uses the 27.00R49 tire which is 106.2" in diameter which would be 7.58" tall, so using the 2.2 tires from rc4wd would be way off scale unless you were going to build the 777 in 16th or possible 18th scale.... nevertheless I hope my info was useful, and I hope you take on this challenge, if you need any help dont hesitate to ask, If you come down to my show next week I can bring you all my files and info on the 777 with all the pics and specs to help you on your build brother.

[bigford]

hey a thing to remember is our little
cat 345 dont really load quarry trucks.
994 pay loaders do or that front end bucket

[9W Monighan]

Came across this video by accident this evening while chilling out from all the book keeping quoting writing up new orders and invoicing.
This video will make your build simple

https://www.youtube.com/watch?v=hiJotXAlNqE

[TRUCKMAKER]

To bad we can't build them that fast!

[steamer]

I started out with a Tamiya Mammoth to build a Cat 789. The Mammoth was a great place to start as it has a terrific chassis and axle setup and heavy duty axle springs. I made a new box and changed the Engine cover to more suit the bigger model. I also made the cylinders from copper water pipe and brass and steel rod for the cylinder rods. The biggest problem was trying to find proper seals as the o rings didn't last long with the heavy lift.
Here's a link to my build and I'm going to try a couple of rcbrmin multi stage cylinders to get mine going!
Rob

http://www.rctruckandconstruction.co...?t=1350&page=8

[Stuart]

You could try here for tyres: Tyres

7.58" equates to 192mm, they have some at 190mm by 40, 60 or 80mm wide in different tread patterns

I think they will also make what ever size/tread you want.

Stu

[Cooper]

Thanks stu, it might take me some time to figure out that site but looks good so far!!