Ok so I have gotten a lot of question this weekend about the new Big Ripto. So I'm going to take a moment and and try to answer as many as I can.
Big Ripto
Ok to start with the breakdown,
the entire frame is 3/16" ar400
the base .08 4130
all welded up with top plates and rail supports brings it to 13.5 lbs
the weapon is 7/8" thick s7 with a 9" spinning dia. mounted to its hub assemble brings it to 7 lbs 15.5 oz
this leaves me with 8 lbs 9.5 oz for wheels and guts, so let's talk about wheels and guts.
first off the wheels.
the wheels are actually very simple to make. I purchased some 60A Polyurethane rubber tubes of mcmaster. Now I would recommend when selecting tubes that your wall thickness never be more then half the width of your intended tire. Otherwise the tire may be prone to rolling off the hub with strong horizontal forces. After I received my rubber I slide it over a piece of aluminium round stock and used it as a arbor in my lathe. Then I mounted a exacto to my tool post and squared it to the chuck. With a nice slow speed the knife cuts it like butter. Now that I have my blanks I grabbed some UHMW round and made hubs with a flange on one side, the flange should be over at least half the wall thickness to propperly retain the tire. The Acetal pulley acts as the flange on the other side when the whole thing is sandwiched together. Now I would recommend .05" over size on the hubs dia for every inch of tire dia and .02-.03" under size on the width. this really helps seat and clamp the tire to keep it from slipping, It also makes an over sized tire, so plan accordingly. I was planing on using Loctite 406 to glue the hub and wheel together when I assembled them but I didn't order it in time so a quick trip to walmart turned
this up and It hasn't failed yet so I'm content with its performance.
alright, the guts.
Right now the bot runs off a 6s pack of a123s. I designed for a123s because I wanted the option to run it at FI. I may try some 8s lipos next year for moto, undecided as of yet.
For the weapon motor I am using a
KB 44-74 Brushless Inrunner 1500KV. I'm not sure how it might feel about being pushed to 8s but it has size able alu mounts to sink heat and the frame is pretty open for air flow from the disc so I will be testing it out in the future. The speed controller for this is not a definitive component yet. I have some things I would like to try out before I decide on a permanent controller.
The drive

The motors are
1100kv B36-74-15-L Brushless Inrunners which I mounted to a 500 series 16:1 p60. There are some hotter wind and more powerful motors on hobby king but this one would give me a matching speed to my hobby which is what I wanted.
the speed controllers for them are
70a Red Bricks that have been flashed with simonK. there are a couple of setting to play with there but more on that later.
I plan on making a really simple simonK for dummies video that shows the basics of the setting and tools to flash a speed controller this week. I know Its intimidation if you are unsure of what you are doing so I want to try and make it more accessible for everyone.
alright i'm out for now.
-Kyle