SUPER B - 60 MPH FIELD TRACTOR [2016 Build-Off Entry]

At the moment, its a 16hp twin that i had fitted twin motorbike carbs to months ago, (and thats as far as i got), i still have to make the engine work with the carbs.  i am looking to fit a different ignition system to the engine to allow for spark advance through the rev range, other than that i want to keep the engine fairly stock.

700 transmission from an old murray rear engine

kart axle, old wheels and tyres from the mini Davy Brown tractor

Seat and steering wheel from a go kart.

i want to build a machine that will travel fast over fields but also be fit to tackle some more technical off road obstacles... and pull a trailer if asked! love set myself the goal of 60mph.

going to have to build the chassis, might try and find an old wide body chassis to form the basis of it.

rear axle on a 4 bar link with a chain drive, could be tricky, want to do independent wishbones up front.

its looking like ill need to build the body again,.. I'm thinking a blue tractor this time?...

That looks like its going to be awesome! This thing looks like it will be a monster!

Wow! 60mph! I am really going to watch this. Go on Northern Ireland haha!

the little country that could lol

https://www.youtube.com/watch?v=AuR9KVyZ2I4

i did this video last night, late last night lol, to run-thru what i was thinking re the build, forgot to link it with the initial picture up above , which btw looks like it was taken with a potato

Looks good!

Awesome build!! Yah, at my age suspension is a necessity, LOL. I had to build my kids mini bike with a soft tail just so I can ride it. 4 link in the back should be good. I'm actually planning on something like that for my racer when I build it, but I was planning on running a belt to the back. Don't know if a chain will work. That ignition box is a great idea too. A wise man told me " If you build for torque, horsepower will follow"

Doin 60 in a field, got ta love it!!!

Yeah the chain throws in a few problems, but i guess also a few solutions, as you know with any design there is compromise, what technical annoyance ill have to put up with re the chain drive will hopefully be offset by the ability to mount the seat and tractor low

Originally i wanted to go triangulated 4 bar link as i outlined in the video - don't worry its still going too be a 4 bar backend With most triangulated 4 bar axles, they are shaft driven, like on a 4x4 or the rear of a drag car, so this is not a problem. But in this application we have that chain.

Initially i had seen baja karts and liked the rear axle setups on them, for those who don't know, baja karts are like a junior level motorsport where the kids drive mini buggies resembling baja trucks, they have ids up front and an array of different rear axle types out rear. they are powered by either mx engines or maybe even ope engines with cvt, i never paid too much attention to the power plant, as it was the suspension that i was interested in. Anyways, there are a couple of different variants of baja kart back ends, quad bike type, independent rear swingarms with independent chain drives, independent swingarms with a single chain drive down one swinger and a weird 3 piece telescoping bendy axle, 4 bar links with a panhard - and triangulated 4 bar links.

The triangulated 4 bar takes my attention straight away, as an engineer I'm always drawn to the simplest solution, as it will usually be the best and easiest to make a good job of making. Plus it looks the coolest . The thing is, to achieve the triangulated 4 bar link, they had actually done 2 things that i had not noticed until today - i mean i had noticed them for sure, just not to the full extent of their function.

Firstly the back axle is mounted inside a welded assembly which resembles a 4x4 axle casing. Among its more obvious functions, this structure braces the kart axle inside so that it is not subject to the full loading of the chain drive and suspension linkage. This protects the axle from getting bent by the forces from the drivetrain.

Secondly the chain drive is fairly central on the axle, this means that the force of the drive is more evenly spread along the axle, it also avoids a situation where the chain drive might try and pull one half of the axle forwards under acceleration, causing bending of the axle and probably also unwanted handling properties.

looking at my initial design of the triangulated 4 bar, and with these factors in mind, i knew that i had a problem, under heavy acceleration the axle would bend forwards and the axle would wreck itself . i did not want to build a heavy axle casing, (as cool as they are), and i had to have the drive down the one side of the seat for the design to work. So the triangulated 4 bar link is out the window, and in comes a new way of doing the 4 bar...

http://gas2.org/2012/10/09/one-racers-long-road-to-building-a-pikes-peak-ev-racer/

OK it took me a while to work out what was going on with the way they did it, so basically its the same kind of setup as a parallel 4 bar link, but instead of the panhard bar it has a triangulated swingarm underneath the axle with 2 mini panhards/struts going between the swingarm and the axle bearing assemblies, these prevent the sideways movement. The way the back end on this thing works is genius, he has a centrally mounted chain drive, but importantly the design will allow for a very lightweight axle setup, and allow me to run the sprocket outboard of the 4 bar like i wanted at the start.

Looks like he's running a double roller chain too. Pretty complex, and definitely light. Looks to be maybe 1 inch to 2 inches of twisting movment on the wheels that can happen. A chain should be able to handle that.

Yeah, chain can cope with a fair bit, although i want to minimise rear end crossaxle as much as i can for handling reasons so a stiff anti roll bar at the back and nothing up front.  i hope to have the weight bias rearwards too so by putting the stiff anti roll bar at the rear the body roll will be well taken care of

idk about 60mph mark, but you definately got the right idea with the motor and seat to keep you in place, good luck!

Thanks man, for sure 60mph is a big ask, and I reckon I may have to revert to a few 'plan b's' along the way.  Keeping the weight down will be key to this working, same as with the little b, with the added torque of a OPE engine though I think its achievable.

The beauty of these engines is that they share, (largely), the same mounting pattern so if I need more power and can get a bigger engine, the chassis doesn't necessarily have to be modified too much, so it leaves me with more options. With the little b the engine power was limited by the fact that the engine is an electric start pitbike engine for packaging and practical reasons, (theres only a limited amount of tuning you can do to the e start ones), I may still re engine it in the future, but it will be a big job.

With the little b I built the chassis around the engine, so the first job is to build the engine, I have a widebody race tractor that I can use as a test bed, so it will hopefully have the vtwin installed by the end of the spring for testing

just as a wee update, this is why I've been slow to start the super-b lol, finally we got round to painting my racer up, (i'm a big days of thunder fan lol), but it will be finished up in the next day or so, and the super-b then starts in earnest!

a couple of things may have changed in the design department with the super-b however, (and this is likely to continue for the first few months). i see a lot of your rock crawler/bouncer off road tractors and a few of you run quite a large front wheel diameter compared to stock. On my tractor i figured that the small front wheels would be the weak point with regards to grip and handling - and i wanted to sort that out whilst still keeping a look reminiscent of a larger tractor - then i remembered these...



I think i could base my tractor on the equal wheel type design of a County, the wheels would be smaller in scale than the body, kinda like the little-b, I dunno how many of these made it over to America or Canada, but they were largely Ford based and very capable, I've wanted one as soon as i first laid eyes on one lol, i think i could make do with a fast mini v twin one for now eh

Nice racer! 12 horse Briggs?
Ah county tractors. I think equal sized wheels look good tbh.

MatthewD wrote:

Nice racer! 12 horse Briggs?
Ah county tractors. I think equal sized wheels look good tbh.

Thanks Matthew yep flathead 12hp I/C, still waiting on a different rear sprocket to sort out the gearing and some more paint for some detail stuff

ill do a concept sketch over lunch today, should help me work out the dimensions

STUNTMAN JON wrote:

just as a wee update, this is why I've been slow to start the super-b lol, finally we got round to painting my racer up, (i'm a big days of thunder fan lol), but it will be finished up in the next day or so, and the super-b then starts in earnest!

and what Days of Thunder fan doesn't LOVE the Mellow Yellow car?

Dude, love the rims. Where did you get them? Are they 5" go kart rims? If not what are they off of?

Thanks Jonny, they are 6" go kart rims, not so common in the uk, they use them on 'long course' or endurance karts - and group 4 uk lawn racers!

they are called Ross Edwards wheels and i think they come from Australia! i got mine from zipnorth go kart shop in England, but i think you can also get them thru the lawn racer guys like ronsbits.co.uk. they use the same standard 3 bolt hub pattern that a uk go kart uses, not the larger 3 bolt USA pattern that you would find on the 6" Douglas wheels you see on a lot of US race mowers, which is good for us because getting hubs and stuff for all that is a compatibility minefield :/

rstolz wrote:

STUNTMAN JON wrote:

just as a wee update, this is why I've been slow to start the super-b lol, finally we got round to painting my racer up, (i'm a big days of thunder fan lol), but it will be finished up in the next day or so, and the super-b then starts in earnest!

and what Days of Thunder fan doesn't LOVE the Mellow Yellow car?

exactly , and who builds a days of thunder replica without re-enacting the car building scene lol

STUNTMAN JON wrote:

rstolz wrote:

STUNTMAN JON wrote:

just as a wee update, this is why I've been slow to start the super-b lol, finally we got round to painting my racer up, (i'm a big days of thunder fan lol), but it will be finished up in the next day or so, and the super-b then starts in earnest!

and what Days of Thunder fan doesn't LOVE the Mellow Yellow car?

exactly , and who builds a days of thunder replica without re-enacting the car building scene lol

great, now I need to watch it again... probably followed by top gun.

Well guys, its been far too long since i updated this, but thankfully the wheels of progress are still slowly turning for the SUPER B.  I tend to spends a fair bit of time planning a project, then i get all the bits, (or most of them), then i start to build the thing in one big go!

Lets start where i left off, v twin 16hp vanguard, carbs dummied on, and a pile of random bits.

well first thing was i stripped the engine right down to the bare casings, cracked it open, all nice enough inside, removed all trace of the governor, and cleaned it all up ready for rebuild.

For this engine i will tune it in 2 stages;

Stage 1: twin carbs, no governor.  thats what the engine is being rebuilt to now, (in my bedroom lol)

Stage 2: is where i introduce the CDI ignitions, but this is after the carbs are at a ballpark tune, and won't be for a while yet.

To mount the carbs properly to the heads i turned a spacer for each on my wee lathe.  The circular bore of the carb needed matched to the 'D' shaped bore of the vanguard head, for this i used a die grinder and shaped the inlet of the head until it matched the round bore of the carb manifold.  The spacers feature countersunk holes and screws and dowels to ensure that the head, spacer and manifold all line up perfectly when assembled for the best airflow.





so currently this is all going back together, took a while to gather all the bits, its an early 16hp and has wee skinny head gaskets which took a few weeks to get :s silly ***** like that.

THE TEST MULE! so in my last posts i mentioned the lawn racer i had been building, (which was holding this project up :s), anyways, i built it with a seriously strong transmission because the plan was always to use it as the test bed for this engine, the thing is bonkers for only having a briggs 12hp flathead, Its ready to do its bit!

CAUTION - POTTY MOUTH AT THE END OF THIS VIDEO - SORRY


I have gathered most of the bits i need to build the front end, (by which i mean - axle, suspension, steering...), so this includes a big pile of rose joints, a load of steel tubing, and 2 mountain bike air shocks.



OK so theres 3 in the photo , one of them has to go back as it was sent out wrong, the 2 red ones are a matching pair.  Chiefly i have a design i am happy with, (hence all the stuff got bought ), it is a single wishbone pull rod type axle and should be nice and compact allowing more space for engine! this will be the first part of the chassis to get built, the whole front end assembly.

What kind of lathe do you have? I was thinking of getting one of those 12" cheap ones for working with small engine stuff. How do you like yours? Getting fancy with the suspension huh? Looks like a formula one setup almost.

http://www.arceurotrade.co.uk/Catalogue/Machines-Accessories/Lathes/Model-C3-Mini-Lathe/Model-Super-C3-Mini-Lathe/Model-Super-C3-Mini-Lathe

its something like 330mm long bed 100mm bed to centre, works well like, you will spend more on tooling than the lathe ever cost you though, they don't like parting off just so much because they don't have the stiffness in the tool holder, but with patience it can be done. most people prefer to part off with a saw unless it is crucial to the part to part-off in the lathe.

thing has paid for itself in a short enough timeframe though

i wanted front suspension that you couldn't see, so it didn't ruin the tractorish look, with any luck it works out quite discreet whilst still effective. it was actually f1 that gave me the idea lol, watching the coverage and them talking about pull rod suspension in the ferraris, then it clicked

Never heard of bike air shocks. The airbag would be the spring? If so, tuning in would be as easy as adjusting the air pressure. Any adjustment for the shock part?

pretty much, its like a pneumatic cylinder and you are correct in that the internal pressure changes the spring rate, thats the main reason why i got them actually, because i have no idea what weight the front of this thing is going to end up as. There are damping circuits also, an analogue adjustable rebound circuit and a compression adjust dial.

The compression adjust is a bit strange because it is for a mountain bike, you essentially have 2 separate compression circuits, a very stiff one, and a more open one, the stiff one is preferred when you would be pedalling, and the more open one would be the preferred position for when descending or going over rough terrain. The shock switches between the 2 automatically, its technology derived from Curnutt shocks for Baja trucks years ago, its been adopted by bikes this last 15 or so years. the adjustment dial you have for the compression is called the threshold control, and it basically controls the riders preference to when the shock should change between these 2 circuits.

i had to wait till the best time/price too get these which was part of the hold up, there was no way i was paying anything like RRP LOL