Outer Limits 4x4 Board

Hi all

I've been tossing up the idea of making a mini crawler buggy just for shits and giggles as a new project. The idea is to make it max 35 inch tyres so that off the shelf and out of wreckers parts will be fine without breaking and to keep cost down. It obviously won't crawl the same stuff that a full size buggy will, but the idea is to wheel it at it's own level instead of just doing harder and harder tracks. It's more about the skill of driving than bragging rights.

Tube frame
35" tyres
Motorcycle engine and gearbox
Car differential as a centre diff/transfer
home made portals using an IFS diff and cv's grafted into a homemade housing (this is just an idea and if it all gets too hard i will just bin it)
The aim is to keep it as compact as is possible for tall guy like me to still be able to sit in.

At this stage the first major issue i have come across is gearing.

A V-twin motorcycle engine and gearbox (light weight and compact) revs to 9000RPM and gets peak torque at about 6000rpm. Thats double an average petrol motor and triple a diesel motor in an average sized fourby. Add to that the first gear is only 2.7:1 compared to 4.5:1 in a patrol or cruiser and you can see that while the top end speed might be awesome the crawling is going to suck.

Can anyone recommend some divorced transfercases that i can mount back to back that are light and compact? I was thinking something out of a suzuki or something. I need to be able to get the hi/low gearing so that in top gear i can still do 40-50kmh but in low/low/first it will crawl. They need to be divorced tcases so i can just bolt a driveshaft or chain sprocket to them as i don't have the facilities to fabricate a spline drive.

I've worked out that with 4.88 gears either end, and a 4.88 diff in the middle that should make HI range pretty normal.

I was thinking of using either a Toyota or Mitsubishi IFS for the portal diffs, and cutting/shutting the axle in the middle of the CV's with tube to make them longer. Any reason this couldn't work? Any reason i can't fit High misalignment heims to the stub axles of a Hilux or Pajero to make the stub outers join to the fabricated housing to imitate king pins?

Could use the engine and gearbox from a small front wheel drive car. Weld the diff would give you low gearing with the engine longways the orginal left and right drive shaft could be use for front and rear.

this might give you some ideas

http://www.pirate4x4.com/forum/showt...ight=kid+buggy

GT Starlet motor / diff
low ratio hilux diffs

rockcrawler31 wrote:Can anyone recommend some divorced transfercases that i can mount back to back that are light and compact? I was thinking something out of a suzuki or something. I need to be able to get the hi/low gearing so that in top gear i can still do 40-50kmh but in low/low/first it will crawl. They need to be divorced tcases so i can just bolt a driveshaft or chain sprocket to them as i don't have the facilities to fabricate a spline drive.

Lada Niva.

But, I agree with others that a car engine is a much better idea than the motorcycle engine.

chimpboy wrote:

rockcrawler31 wrote:Can anyone recommend some divorced transfercases that i can mount back to back that are light and compact? I was thinking something out of a suzuki or something. I need to be able to get the hi/low gearing so that in top gear i can still do 40-50kmh but in low/low/first it will crawl. They need to be divorced tcases so i can just bolt a driveshaft or chain sprocket to them as i don't have the facilities to fabricate a spline drive.

Lada Niva.

But, I agree with others that a car engine is a much better idea than the motorcycle engine.

fair enough. The main reason is that the MC engine and trans combo is super compact and light. Even a small car motor and gearbox is going to be much bigger, and when you consider the fat bastard going to be wheeling it every bit of space counts

I did a bit of looking around, 35" tyres, 4.11 diffs, 4.88 diff transfer plus a set of 6:1 calmini gears in a zook transfer gives me 1.5MPH in first at 6000RPM and 50MPH in top gear high range. Does this sound reasonable? what is high range gearing in a zook transfer? i was assuming 1:1 when calculating it

bru21 wrote:GT Starlet motor / diff
low ratio hilux diffs

Any idea what rough physical dimensions/weight/power you're looking at with this?

Is it an east west motor? If so how would you go about getting the drive to a transfer?

AFeral wrote:Could use the engine and gearbox from a small front wheel drive car. Weld the diff would give you low gearing with the engine longways the orginal left and right drive shaft could be use for front and rear.

this might give you some ideas

http://www.pirate4x4.com/forum/showt...ight=kid+buggy

I've seen that and yes, it's sort of what i'm aiming at. I'd like to try and do something KOH style but on a smaller scale and price. Basically want to go out to 4WD park or mates properties and either crawl stuff or drive it like i stole it.

On that note - Will a zook transfer case with gears hold up to that kind of punishment with those size tyres? 35's doesn't sound super huge in the big scheme of things given that there will be at least 4.56 or 4.88 diff gears in front of them again

rockcrawler31 wrote:

chimpboy wrote:

rockcrawler31 wrote:Can anyone recommend some divorced transfercases that i can mount back to back that are light and compact? I was thinking something out of a suzuki or something. I need to be able to get the hi/low gearing so that in top gear i can still do 40-50kmh but in low/low/first it will crawl. They need to be divorced tcases so i can just bolt a driveshaft or chain sprocket to them as i don't have the facilities to fabricate a spline drive.

Lada Niva.

But, I agree with others that a car engine is a much better idea than the motorcycle engine.

fair enough. The main reason is that the MC engine and trans combo is super compact and light. Even a small car motor and gearbox is going to be much bigger, and when you consider the fat bastard going to be wheeling it every bit of space counts

I did a bit of looking around, 35" tyres, 4.11 diffs, 4.88 diff transfer plus a set of 6:1 calmini gears in a zook transfer gives me 1.5MPH in first at 6000RPM and 50MPH in top gear high range. Does this sound reasonable? what is high range gearing in a zook transfer? i was assuming 1:1 when calculating it

Zook high is a reduction setup. Factory it is round 1.2 from memory, but with 6.5:1 gear set it will be more like 1.6:1 or so. Most reduction gear sets reduce high by around 18%. Zook cases are okay if you brace the mounts and fit a case ring like Chris(rocktoy) makes.

Layto....

any comments on extending CV shafts with a bit of heavy wall DOM tube?

Would you do just a ring weld around the end of the tube, or add a couple of rosette welds along it too?

chimpboy wrote:

rockcrawler31 wrote:Can anyone recommend some divorced transfercases that i can mount back to back that are light and compact? I was thinking something out of a suzuki or something. I need to be able to get the hi/low gearing so that in top gear i can still do 40-50kmh but in low/low/first it will crawl. They need to be divorced tcases so i can just bolt a driveshaft or chain sprocket to them as i don't have the facilities to fabricate a spline drive.

Lada Niva.

But, I agree with others that a car engine is a much better idea than the motorcycle engine.

unless you have a 2.3 from a rocket lying around.
plenty of torque

Jes

rockcrawler31 wrote:any comments on extending CV shafts with a bit of heavy wall DOM tube?

Would you do just a ring weld around the end of the tube, or add a couple of rosette welds along it too?

yeah easy as, you not going to have enough minerals to break them,

What if you ran a FWD engine and auto in the middle, no transfer, straight out from the diff that comes with the engine to front and rear diffs at your wheels? Right out of the box it will have good gearing for driving from 0-50kmh or so, lousy gearing for any faster but as if you are going to go any faster. Less to break, less to weld, less to fark with.

Or is my speedy mental arithmetic stuffed.

what about series 1 rav4 engine,gerbox, + rear diff.

some of them also came with centre diff lock

they are cheap, light, and very ROBUST.

+ you have a choice of engines from the 3s series and others that will bolt up, and with a little modification you can bolt up a heap more.

you can get reduction from the " portals" your running.

Jes

chimpboy wrote:What if you ran a FWD engine and auto in the middle, no transfer, straight out from the diff that comes with the engine to front and rear diffs at your wheels? Right out of the box it will have good gearing for driving from 0-50kmh or so, lousy gearing for any faster but as if you are going to go any faster. Less to break, less to weld, less to fark with.

Or is my speedy mental arithmetic stuffed.

How would you ensure that the FWD diff locks up completely and sends positive torque to each shaft? I think without a transfer it would be too high geared still. They're designed to run what....22-24" tyres at at normal road speeds? 35's would be a 50% increase in gearing.

jessie928 wrote:what about series 1 rav4 engine,gerbox, + rear diff.

some of them also came with centre diff lock

they are cheap, light, and very ROBUST.

+ you have a choice of engines from the 3s series and others that will bolt up, and with a little modification you can bolt up a heap more.

you can get reduction from the " portals" your running.

Jes

I like the engine idea. There would be bugger all low range since IIRC they had no low range gearing but a diff as a transfer would solve that.

My portals idea have no reduction except for what is in the differentials

rockcrawler31 wrote:

chimpboy wrote:What if you ran a FWD engine and auto in the middle, no transfer, straight out from the diff that comes with the engine to front and rear diffs at your wheels? Right out of the box it will have good gearing for driving from 0-50kmh or so, lousy gearing for any faster but as if you are going to go any faster. Less to break, less to weld, less to fark with.

Or is my speedy mental arithmetic stuffed.

How would you ensure that the FWD diff locks up completely and sends positive torque to each shaft? I think without a transfer it would be too high geared still. They're designed to run what....22-24" tyres at at normal road speeds? 35's would be a 50% increase in gearing.

jessie928 wrote:what about series 1 rav4 engine,gerbox, + rear diff.

some of them also came with centre diff lock

they are cheap, light, and very ROBUST.

+ you have a choice of engines from the 3s series and others that will bolt up, and with a little modification you can bolt up a heap more.

you can get reduction from the " portals" your running.

Jes

I like the engine idea. There would be bugger all low range since IIRC they had no low range gearing but a diff as a transfer would solve that.

My portals idea have no reduction except for what is in the differentials

The FWD option works well. Just weld/spool the diff in the gearbox. But its not really suitable for speed work or tar/high traction surfaces. The gearing is okay especially an auto - you have the auto converter - then 1st gear, then the diff reduction then into your acutal car diffs. Say auto 1st is 2.6:1, diff is 3.5:1 and you use 5.29 lux diffs. There is 48:1 plus you have the auto converter.

Layto....

If you want ideas take a look at all the NZ buggies. Most run 35" tyres (35's are max for our comps) and depending on class, 4's 6's or 8's.

First choice you want to make is if you actually want it actually lightweight or just relatively lightweight.

If you really want it lightweight dont even waste time thinking about 35's or portals or toyota diffs or running a transfer etc. They all add weight.

If you want to run with a bike engine, consider hooking it up to a fwd gearbox. Then you will get reverse aswell as a whole range of ratios (a transfer case wont give you this). Though a bike engine will not give you the torque you want. A hayabusa motor would be awesome in one, but they are $$$

For lightweight, you can run a 1"nb tube for the main structure of the frame, and run smaller stuff for anything that is not bent.

I am building something similar. Ive got a swift gti motor and fwd box (I can just lift the whole lot off the ground and im not exactly large). Austin diffs which have alloy diff casings so are really light (i can carry the complete axle assembly around with ease, but really struggle with an empty lux housing. Im running motorcycle forks as shocks with an air fitting tapped into the top of them so I can individually lower and raise them (really light as it negates the need to have a spring and a shock, and they are primarily alloy). Mine is a two seater so is not as light as it could be, and the design means that it is not as light, but its my first time building anything this extensive so im learning for next time. It should end up well under 700kg.

Heres a few pics of some of the new nz ones that are getting churned out. All now running fwd gearboxes.

Turoa wrote: A heap of awesome tech

Thanks heaps mate. Exactly the tech i was after.

The V-twin MC engine gets reasonable torque for what it is. 98NM at 6000RPM standard with no tweaks to motor.

How hard is it to divorce the FWD gearbox from the motor itself? and how do you go about getting drive to the gearbox again from a normal engine or an MC engine?

rockcrawler31 wrote:

chimpboy wrote:What if you ran a FWD engine and auto in the middle, no transfer, straight out from the diff that comes with the engine to front and rear diffs at your wheels? Right out of the box it will have good gearing for driving from 0-50kmh or so, lousy gearing for any faster but as if you are going to go any faster. Less to break, less to weld, less to fark with.

Or is my speedy mental arithmetic stuffed.

How would you ensure that the FWD diff locks up completely and sends positive torque to each shaft? I think without a transfer it would be too high geared still. They're designed to run what....22-24" tyres at at normal road speeds? 35's would be a 50% increase in gearing.

Really? I haven't calculated it but hypothetically, the final drive ratio in (say) a Suzuki Swift is 4.11:1. So that is sitting there instead of your transfer case which for normal dollars is not going to be as high as 4.11:1, probably 2.x:1 at best. So you have nearly double the gearing there straight off.

Then you have 4+:1 again at your new diffs, so that is more than compensating for bigger tyres.

I am just shooting the shit here.

so a quick calculation

FWD motor doing 3000 RPM

2.6 1st gear
3.5 Diff
2.4 Zook transfer (in low range)
4.11 diffs (using shorter diffs for reliability)

= 89:1 reduction and 5.56 K/Hr

or in high range

.95 top gear
3.5 Diff in FWD gear box
1.2 zook transfer in high range
4.11 diffs

= 16.3:1 and 30K/Hr

does this sound like a reasonable compromise?

chimpboy wrote:

rockcrawler31 wrote:

chimpboy wrote:What if you ran a FWD engine and auto in the middle, no transfer, straight out from the diff that comes with the engine to front and rear diffs at your wheels? Right out of the box it will have good gearing for driving from 0-50kmh or so, lousy gearing for any faster but as if you are going to go any faster. Less to break, less to weld, less to fark with.

Or is my speedy mental arithmetic stuffed.

How would you ensure that the FWD diff locks up completely and sends positive torque to each shaft? I think without a transfer it would be too high geared still. They're designed to run what....22-24" tyres at at normal road speeds? 35's would be a 50% increase in gearing.

Really? I haven't calculated it but hypothetically, the final drive ratio in (say) a Suzuki Swift is 4.11:1. So that is sitting there instead of your transfer case which for normal dollars is not going to be as high as 4.11:1, probably 2.x:1 at best. So you have nearly double the gearing there straight off.

Then you have 4+:1 again at your new diffs, so that is more than compensating for bigger tyres.

I am just shooting the shit here.

What sort of rev range and peak torque/rev are we talking about here for these kinds of motors?

rockcrawler31 wrote:

Turoa wrote: A heap of awesome tech

Thanks heaps mate. Exactly the tech i was after.

The V-twin MC engine gets reasonable torque for what it is. 98NM at 6000RPM standard with no tweaks to motor.

How hard is it to divorce the FWD gearbox from the motor itself? and how do you go about getting drive to the gearbox again from a normal engine or an MC engine?

Have a look through this thread http://pirate4x4.com/forum/showthread.php?t=334588

Theres a few bits about an mc powered buggy in there. Not long after I started my buggy build i was given a smacked up v twin yamaha that I would have tried out the motor in my buggy had i not already bought the swift.

Most guys here don't worry about divorcing them as a good weight balance is mounting the motor low enough and back far enough to run a front shaft (so the front pulley is behind the axle tube).

BTW this spreadsheet might be handy for you; I made it ages ago.

You can add gearboxes, transfer cases, and diffs to the tabs of the spreadsheet and then just reference them by their labels. Other than that all you type in is the yellow bits on the front tab.

http://members.optusnet.com.au/~chimpbo ... ratios.xls

Those buggies look like they would be good fun, will be watching what you come up with here

Ok done the maths on chimps suggestion of a FWD Swift GTi motor with 4.56 diffs = 70Km/H in top gear doing 6000RPM

1st gear at 3500RPM (peak torque) is 9km/h - is this going to be slow enough?

Also, if you weld the FWD diff up, how strong is the output on that going to be? will it cope considering it will be going straight to the pinions on the diffs. with the diffs and tyres it will be similar if not slightly lower than what the car originally saw on the road, but then i've never seen swifts trying to climb rock ledges with the tyres wedged into corners giving it the berries either.

rockcrawler31 wrote:with the diffs and tyres it will be similar if not slightly lower than what the car originally saw on the road, but then i've never seen swifts trying to climb rock ledges with the tyres wedged into corners giving it the berries either.

With (say) 4.1:1 diffs and 35s, that is equivalent to running directly out to something like 8.5" diameter tyres.

Anyway what about just having LSD in the centre diff. http://grassrootsmotorsports.com/forum/ ... 299/page1/

But I dunno whether engine/gearbox out of an FWD vehicle will actually fit sideways...?

A motor cycle engine would leave you without reverse, this would be a big disadvantage in a lot of situations. Backing down a tricky rocky incline for another shot at it would be interesting with no reverse, or backing off a rock or out of a hole?

80's_delirious wrote:A motor cycle engine would leave you without reverse, this would be a big disadvantage in a lot of situations. Backing down a tricky rocky incline for another shot at it would be interesting with no reverse, or backing off a rock or out of a hole?

I saw an article on an offroad racer that was built using a big moto engine and gearbox, cbr1100 or something similar but with no reverse, that problem was solved by using a starter motor that ran onto the chain, he reckoned it worked great

what about the honda motors? they came with a nice auto, could be fun with the vtec

ive been thinking of a buggy like this for a while and was reckoning that a honda vtec+auto+welded diff +4.88 bundy axles + 35's would be fun

chimpboy wrote:What if you ran a FWD engine and auto in the middle, no transfer, straight out from the diff that comes with the engine to front and rear diffs at your wheels? Right out of the box it will have good gearing for driving from 0-50kmh or so, lousy gearing for any faster but as if you are going to go any faster. Less to break, less to weld, less to fark with.

Or is my speedy mental arithmetic stuffed.

thats the way... Mock's old OZrock buggy was set up like this, 4cyl out of a camry. worked well, except for high speed stuff.

no transfer...