# fast mini buggy



## galderdi (Nov 17, 2015)

Hey,

Your plan sounds sort of similar to my two projects. Although mine are designed mostly for bitumen. You can see them here:

http://www.diyelectriccar.com/forums/showthread.php/aussie-ev-autocross-special-ii-185897.html


http://www.diyelectriccar.com/forums/showthread.php?t=166009

My first one weighed around 1155lbs and was a front wheel drive two seater. My new one weighs around 1008lbs and is a mid engined single seater. Unless you are continually stopping and starting I don't think your batteries will need to sit at more than 500 amps for long. 

For 25 minutes of hard driving you'll need at least 7kwh of capacity (that is what I have). But I recommend aiming a little higher.

I run a full gearbox, which adds to the weight but means gearing is no issue. If you choose to run without a gearbox I suggest aiming for the equvalent of 3rd gear. In my car 2nd gear gets me just around 60mph but 3rd would be more comfortable.

Wheelspin on dirt was a real issue for my first car as it was front wheel drive. You can see the videos if you search for "Full Charge Motorsport".

I can't help much with those CALB batteries. But let me know if you have any questions about the rest of my builds.


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## Jonbickford (Feb 27, 2018)

I read through your newer car thread a couple of days ago that thing is awesome! 

something similar to that for sure but a bit smaller and lighter and less powerful. I'm aiming for about 75mph top speed it doesn't really need to go faster than that for now. Being from Australia you might be familiar with Edge buggies, I want to do something kind of similar to their lightest weight suspended model. 

The battery pack is at about 5.1 kWh as I'm currently picturing it and the idea would be to have 2 packs with 48lbs of battery in side pods on each side of the driver and have a second pair of packs to swap out. Trying to stay on budget and in the performance envelope I'm aiming for is tough and means some over simplified suspension and various compromises like that for cost, and weight.

I hadn't seen your first buggy yet that thing is really cool too! I love the video where they have you doing slalom between two concrete walls! too many lawsuits in America to do stuff like that anymore! very cool.


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## galderdi (Nov 17, 2015)

Thanks, Yeah I am quite happy with how both turned out.


Sounds like you have a good idea of your target and a good plan.

If you skipped the gearbox you would probably bring the weight down to around 970lbs.
If you went with a lower power motor you might bring it down to 950lbs.
My roll cage and other safety features are designed to meet my sport's standards so you might save some more weight there.
My wheels, brakes etc are all designed to take the force of running on bitumen so you can probably run with lighter wheels, tyres and brakes to save more weight. 
My batteries are around 135lbs so you can probably save some weight there too.

I am also sure someone with more experience could build the rest of the chassis lighter than mine. But mine is built to take some significant forces and I am guessing yours would need to be similar. However if you build a good roll cage you can use to add strength to a light weight floor.


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## Jonbickford (Feb 27, 2018)

I am planning on doing just a chain drive, I may even do just a solid live rear axle on an ATV style swing arm to save a lot of weight. Not ideal for handling but in the spirit of "simplify and add lightness" I've also considered having the motor spin a jack shaft then running 2 sprockets on the shaft and 2 chain driven trailing arms in back. 

Anything to keep the weight down and the strength up at this point at the expense of tidy handling, at least the center of gravity will be very low! Sideways isn't fast but it is fun and looks good on youtube! haha.


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## brian_ (Feb 7, 2017)

Jonbickford said:


> Being from Australia you might be familiar with Edge buggies, I want to do something kind of similar to their lightest weight suspended model.
> 
> The battery pack is at about 5.1 kWh as I'm currently picturing it and the idea would be to have 2 packs with 48lbs of battery in side pods on each side of the driver and have a second pair of packs to swap out.


So, the Sidewinder Plus, I assume. This would be an interesting configuration. It would be nice to have better suspension, though... the upgraded front suspension and something independent (or at least articulated) at the rear.


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## brian_ (Feb 7, 2017)

Jonbickford said:


> I am planning on doing just a chain drive, I may even do just a solid live rear axle on an ATV style swing arm to save a lot of weight. Not ideal for handling but in the spirit of "simplify and add lightness" I've also considered having the motor spin a jack shaft then running 2 sprockets on the shaft and 2 chain driven trailing arms in back.


That's was the Sidewinder has, but the idea of a suspension which forces the whole vehicle to roll with ground irregularities wouldn't work for me. It's not so bad on an ATV such as a quad that you straddle like a motorcycle, because it can toss around without your body moving to match, but strapped in a seat is different.

Still, lots of inexpensive sit-in ATVs have used this design.



Jonbickford said:


> I've also considered having the motor spin a jack shaft then running 2 sprockets on the shaft and 2 chain driven trailing arms in back.


Well, individual chains per wheel worked for antique trucks... 
It actually does make mechanical sense to me in this case.


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## Jonbickford (Feb 27, 2018)

yes exactly! the sidewinder plus was the initial inspiration, but It would be even cooler to stuff the motor behind the driver's lower back since it's only 7" diameter and 14" long, then close in those nerf bars to where they are basically side pods to carry batteries on each side. 

I've only seen a couple of photos out in internet land with dual chain drives, It seems like a really simple and light solution and no worrying about cv joints handling electric torque... it might even be possible to make it weigh as little as the single swing arm since it doesn't have to take all the huge torsional forces though I suppose the jackshaft and extra chain and shock would take that advantage back.


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## Jonbickford (Feb 27, 2018)

for expediency sake I may just do the sidewinder plans with the motor on the side and try to break up the battery packs to counter balance it out. then once I'm really happy with the power work on another design from scratch but I also wonder, how much more effort is it to just do my original design the first time?

I would like to have it rolling by the end of summer.


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## Jonbickford (Feb 27, 2018)

there is also the option of doing something like the majority of cheap Chinese buggies do where they have the engine mounted to the swing arm, run two shocks and have some side to side absorption where the swing arm is sorta floating free a little bit. that's also popular for on road rc cars. 

the AC23 weighs 60 lbs but since it's so small in diameter I think it could be mounted right at the very top of the swingarm above the pivot so it doesn't move very far with the suspension and lessens the beating the motor takes and the adverse effect of unsprung weight as much as it possibly could.


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## brian_ (Feb 7, 2017)

*rear suspension*



Jonbickford said:


> there is also the option of doing something like the majority of cheap Chinese buggies do where they have the engine mounted to the swing arm, run two shocks and have some side to side absorption where the swing arm is sorta floating free a little bit. that's also popular for on road rc cars.


This generally sounds like some sort of live beam axle on a locating frame which also carries the motor. Once you allow articulation (roll motion, or different travel on left and right sides), the simplest construction uses a big ball joint at the front, an A-frame to the axle, a couple of springs and shocks... and something to locate it side-to-side, such as a Panhard bar, Watt's link, or various more strange contraptions. It's that last bit which causes all of problems and complicate the structure, and by the time it's done well, I think it might as well be independent... even if that means the simplest trailing arms.



Jonbickford said:


> the AC23 weighs 60 lbs but since it's so small in diameter I think it could be mounted right at the very top of the swingarm above the pivot so it doesn't move very far with the suspension and lessens the beating the motor takes and the adverse effect of unsprung weight as much as it possibly could.



If you do a single non-articulating (no roll) arm you can make the arm pivot on the same axis as the motor, or the same as the jackshaft (if using a two-stage chain drive); a differential would go on the axle line.
If you do two independent trailing arms, you can go without a diff or with a diff on the jackshaft (if using a two-stage chain drive or first chain stage plus half-shafts). If it is a two-stage chain drive you can again pivot the arms on the axis of the jackshaft.
Either eliminates any motor motion or chain length change with suspension motion at all.


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## brian_ (Feb 7, 2017)

*Side-mount motor?*



Jonbickford said:


> for expediency sake I may just do the sidewinder plans with the motor on the side and try to break up the battery packs to counter balance it out.


I was thinking of the motor behind the seat, but I suppose with a heavy motor it could sit on one side with the controller and every other bit of hardware needed, and the entire battery on the other side.

With the motor on the side, a first stage chain drive could go back to a jackshaft behind the seat, and whatever is chosen for suspension and final drive from there.

Whether there is no battery or only a small battery section on the motor side, it seems like a limitation on battery size, and awkward for packaging easily handled battery packs. Meanwhile, there's not much useful happening behind the seat.


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## brian_ (Feb 7, 2017)

*front suspension*

Would it possible, and expedient, to salvage an entire front suspension with hubs from an ATV? People must wreck these things frequently, but I suppose the front end bits might not survive very often; perhaps a used machine with a dead engine might be a more likely source.


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## Jonbickford (Feb 27, 2018)

completely agree on all points Brian! putting the motor right behind my butt with the shaft inline with suspension pivot is pretty much the most likely scenario I'm thinking, same concept as the sidewinder but with the motor in the middle of the swing arm pivots instead of to the side. I figure that would also protect the motor and chain a bit more and give me a lot of room to do what I want with the side batteries just like you said. it's also just a lot more elegant engineering and with such a small motor you don't really have to stretch the wheel base much at all from the sidewinder plans! on paper at least my design is actually a little smaller than the sidewinder in every dimension.

The dual chain trailing arms would be great, I could mount the jackshaft right behind the seat and the motor could be hung back behind that. 

of course, if I went with dual chains I could have the option of running dual motors! but I haven't really found anything small that can match the power to weight ratio of an hpevs AC20/23 motor.

I've absolutely been looking at atv suspension on eBay and craigslist! a lot of people hop up their RZR and sell the original shocks and suspension arms off for pretty cheap, there's also a big aftermarket of heavy duty widened atv suspension kits available. if I figure out what model I want to use as a basis I should be able to get a pretty nice front suspension that way if not also the rear.


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## Jonbickford (Feb 27, 2018)

how do I post pics on here? you guys seem to get exactly what I'm talking about but visual aids are always great.


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## Jonbickford (Feb 27, 2018)

this is the coolest looking 2 chain setup I've found on the web so far I wish I could find more info about the car, but honestly, that looks great!


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## Jonbickford (Feb 27, 2018)

these little cars are apparently a 600cc spec series in Finland, they have a side mounted engine and are pretty close to what I'm picturing. I've watched a lot of videos of them racing and the handling does leave something to be desired! at least in this case the batteries and motor will all be 8" off the floor and the only mass higher than that is roll cage and the driver's upper body.


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## Jonbickford (Feb 27, 2018)

I want to stick to the size of a Honda Pilot basically. that is a buggy you can carry in the back of a pickup truck. The driver could sit further back so that his feet are behind the front axle line for safety because it doesn't need the space for the large bike engine behind the driver, and with the batteries on the sides the mass will be concentrated nicely between the axles, with longer side pods I can slide the batteries forward and back to play with weight balance. or just play with bigger batteries...


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## Jonbickford (Feb 27, 2018)

in the case of the sidewinder, it's not ideal but it is the closest thing in terms of size, weight, strength and cost to what I had in mind for the original design goals that I have found! I could definitely make a fun buggy off of one and focus on the electric end not having to also worry whether my first ever blank page chassis design is sound.


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## Jonbickford (Feb 27, 2018)

back of Edge Sidewinder Plus.


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## Jonbickford (Feb 27, 2018)

a couple of rough sketches for scaling, I wanted to try and fit the whole thing within a 4'X8' footprint and did so pretty easily, the easiest way to make something lighter is to make it smaller...


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## brian_ (Feb 7, 2017)

Jonbickford said:


> ... of course, if I went with dual chains I could have the option of running dual motors! but I haven't really found anything small that can match the power to weight ratio of an hpevs AC20/23 motor.


Two motors would avoid a differential, but require two complete chain drives and two controllers. Unfortunately I don't have a suggestion for a suitable motor.


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## brian_ (Feb 7, 2017)

Jonbickford said:


> I've absolutely been looking at atv suspension on eBay and craigslist! a lot of people hop up their RZR and sell the original shocks and suspension arms off for pretty cheap, there's also a big aftermarket of heavy duty widened atv suspension kits available.


Good idea, but the take-off original bits won't include the hubs and hub carriers because the RZR owners re-use those... so you still need them from somewhere. At least if the stock bits are suitable for your machine, there's a ready source of replacement parts in case of damage.



Jonbickford said:


> if I figure out what model I want to use as a basis I should be able to get a pretty nice front suspension that way if not also the rear.


The rear as well would be ideal... but of course means using the original axle shafts and thus a somewhat different transmission/final drive setup. It would be easy to put the motor behind the seat without stretching the wheelbase when the motor can sit immediately ahead of the axle line.


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## brian_ (Feb 7, 2017)

Jonbickford said:


> this is the coolest looking 2 chain setup I've found on the web so far I wish I could find more info about the car, but honestly, that looks great!


It's hard to see fine detail, and in a Google search I didn't even find that image - let alone more detail - but it does look reasonable.


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## brian_ (Feb 7, 2017)

Jonbickford said:


> back of Edge Sidewinder Plus...


The stock rear suspension design certainly limits you to both a side-mounted motor and no axle articulation. That side chain would be unworkable if the axle were allowed to articulate (roll).

If you copy the size and general structure of the Sidewinder, but not any of the suspension details, you can avoid these limitations.


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## brian_ (Feb 7, 2017)

Jonbickford said:


> ... I wanted to try and fit the whole thing within a 4'X8' footprint...


Ah, yes, the "fits in a pickup truck" size!


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## Jonbickford (Feb 27, 2018)

yeah if I can keep it down to a truck bed size and the weight down to around my original target of 700 lbs I would be able to fit the car with batteries installed, two sets of spare batteries and some aluminum atv ramps in the back of a 1/2 ton pick up with no problem! if I can engineer that to where the whole caboodle comes in under $15k using new parts with repeatable results then I have hit all of my initial fantasy design goals! that would be amazing!

right now I know that my motor and controller are $3k, a set of adequate batteries costs $2000-$3000 depending on how I work it, the sidewinder plans CLAIM you can DIY a rolling chassis for around $3500 Australian which I think is about $3000 USD, so if I can match the price and weight parameters of a sidewinder build with a slightly smaller footprint then I have pretty much hit my initial goals exactly on the head! 

I don't know how accurate the rules of thumb are but according to the EV4u guy I should be able to get about 57 miles of theoretical cruising range out of a 900lb driver/car combo and a 5.184 kWh battery (72vX72ah). another rough rule of thumb would be that it takes 3x as much energy to drive hard and fast as it does to cruise at a constant speed, so if that knocks it down to about 19 miles of range of tire spinning, sideways jumping fun most Moto tracks and go kart tracks are less than 1/2 mile so that's approaching 40 laps which is plenty of adrenaline in between breaks to swap batteries!!

if my goal is to thoroughly outperform a sidewinder their recommended engine is a 650 Kawasaki that weighs 125lbs, then there's a big oversized gas tank on the left to try and counter some of the engine's weight... with a 60lb motor and 88lbs of batteries I'm at 148 lbs! so I'm probably right about on par with the weight of the ICE sidewinder! I also have MUCH better center of gravity and balance! the Kawasaki engine makes around 32hp so I would already have more than 30% more horsepower and while I don't know how much torque the Kawasaki makes it damned sure isn't going to be 105lb/ft at 0 rpm!!!

I'm really enthusiastic right now because I came up with the initial idea and design parameters I would want a couple of years ago but not knowing anything about electrical engineering and not much practical knowledge of chassis design I didn't really think I could check all my fantasy boxes and stay within the size/weight/cost/power/range requirements. but in the last few months my knowledge base has finally gotten to the point where WOW! I really think I can make this work! what started as thoroughly uneducated,"about yay much" measurements actually seems to make perfect sense on paper now and right on target! 

So now I HAVE to do it.


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## Jonbickford (Feb 27, 2018)

a couple years ago I even figured that if I could keep the battery packs down to 50lbs each that is an amount that anyone healthy enough to be ripping around in the buggy ought to be able to lift! I had originally figured on 3 packs, 24v each pack because that's a small enough voltage that it is fairly safe for people to fiddle with it. 2 packs on one side weighing 100 lbs and one 50lbs pack on the right in front of the 60lb motor in sidewinder configuration. but now I have got it down to 2 packs of 36v 11-12 cells and the cells only weigh 44-48lbs, by the time I add connectors, some kind of structure and a handle it's 50lbs each! another detail that is coming in exactly on my completely ignorant, "about yay much" early fantasy target!


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## Jonbickford (Feb 27, 2018)

AND I've been thinking the last couple days that if I leave enough room in the side pods for another set of batteries I could wire the packs on each side in parallel and add 100lbs while also doubling to a 10.3 kWh battery pack and the car still weighs 1000lbs with the driver and at that point It would have enough range to leave the short course and go trail riding with my dirt bike or sandrail friends! ...or, I could wire the extra packs in series and swap out a 144v controller, the damned thing would make 76hp at that point!

so you would have the option of running 20 minute "Moto" packs that you swap out or use both sets of batteries at once for, "endurance mode"

...or, I could wire the extra packs in series and swap out a 144v controller, the damned thing would make 76hp at that point! that's right on par with extremely serious alcohol fueled atv drag racers!

if you can't tell I'm REALLY getting excited about the way the numbers are starting to actually shape up!


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## Jonbickford (Feb 27, 2018)

as for a differential... certainly I could work a kart style differential into either the jackshaft or a solid rear axle easily enough, but I'm leaning against it at the moment. with so much instant torque on such a short wheelbase I expect to steer with the throttle pedal as much as the steering wheel! Sideways isn't fast but it sure is fun and looks awesome on youtube! the main problem I have with the diff is that I would then need two rear brakes instead of a kart/atv style single rear disc and of course that will run the cost and weight up. 

I figure if I crank up the regen on a live axle just taking my foot off the throttle abruptly should provide more than enough throttle off oversteer to turn into a corner! hahaha!


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## Jonbickford (Feb 27, 2018)

a few more thoughts about brakes, differential and the dual chain lay out. I've always cringed a bit when I see inboard brakes on a classic racer! trusting the c.v. joints to handle your stopping power always seemed a bit foolish to me... if I did the jackshaft dual chain idea and used an atv style single brake I would be asking the chains to handle all the braking force. I guess if one of them failed you would still have one rear wheel brake functioning. and on the flip side if I broke one of the two drive chains out on a trail I could limp home with 1 wheel drive so that's pretty cool. without a diff if I had brakes on both wheels and one caliper failed id still be sending stop force to that wheel via chain from the other wheel so that's kinda cool too.

of course, if I have 3 chains in the driveline I'm 3x as likely to have a chain fail! I also have the cost and rotating mass of 3 chains, 6 sprockets, 2 brakes AND 2 coil over shocks instead of one chain and 2 sprocket direct drive, one brake disc and one shock! as much as I want to get fancy pants I keep reverting back to the simplest answer!


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## brian_ (Feb 7, 2017)

I think the straightforward way to get reliable and effective braking is just to use conventional outboard brakes. If there's no differential, that would give you braking redundancy as well... but personally I wouldn't want to either depend on chains for braking or put braking force on a chain in normal operation.


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## Jonbickford (Feb 27, 2018)

I think I may have come up with something last night that would give me side to side movement on a solid axle without becoming a complicated mess or adding too much cost and weight, a second shock, a small amount of extra metal and a pair of extra bushings would be all it would add to the weight. possibly a pair of small springs to provide adjustable roll control as well...


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## brian_ (Feb 7, 2017)

Jonbickford said:


> I think I may have come up with something last night that would give me side to side movement on a solid axle without becoming a complicated mess or adding too much cost and weight, a second shock, a small amount of extra metal and a pair of extra bushings would be all it would add to the weight. possibly a pair of small springs to provide adjustable roll control as well...


Suspension design is one of those areas where just about everything has already been done, and there's good reason if it is no longer being done, but I'm interested to see this idea.


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## Jonbickford (Feb 27, 2018)

I don't know what it is actually called so I'm calling it a T bar.

picture an atv style swingarm, this is attached at the pivot to a T shaped component, the lower part of the T is laid down on the centerline of the chassis and held with bushings. the T is allowed to swivel side to side say, 22 degrees or so, this lets the swingarm move side to side. unlike a ball joint and triangle to the axle design the T bar doesn't need any other assistance keeping the rear wheels pointed straight ahead.

the motor is mounted to the swingarm Chinese style but at the very top of the swingarm, above the pivot point, that way the leverage of the swing arm moves the motor the least amount possible and has the least drag on the suspension, the up and down movement of the suspension converts to a small movement of a few inches forward and back for the motor.

2 shocks would be used in pretty standard fashion, controlling up and down as well as side to side on the swing arm.

in sand dunes or rock crawling you want as much articulation as possible but then you're dealing with body roll in corners on a grippy surface, I started thinking about how a sway bar would work and decided I could use sway springs instead... if the T bar has a tab sticking up on the center shaft you can put walls on either side of that tab and use adjustable bump stops to control just how much side to side travel you have, but you can also place springs on either side of the tab that would act as anti-roll control... stiffer springs create more roll resistance and does it completely independently from the up and down motion of the swing arm! that way a softer more compliant spring rate can be used at the swing arm and body roll is completely separate, the 2 shocks would still absorb motion side to side in a dampened way so the roll springs wouldn't feel harsh or bouncy I don't think.

this would allow me to use a cheap atv axle and single rear brake the only extra weight and cost one a sidewinder style swingarm would be the second shock, bushings for the T bar, the metal itself and some undampened smaller springs.

another thought I had is maybe a little more far fetched... if the 60lb motor is mounted on the swingarm above the pivot, under hard acceleration the weight of the motor would be pushing backward which would be pushing the swingarm downward... perhaps a little bit of inertia based anti squat?? under hard braking the motor would want to swing forward, lifting the swing arm, perhaps that has an anti-dive effect or perhaps it just means the rear wheels lock easier?

pardon the sketches I whipped them up real quick, I never took drafting my sketches have only ever had to make sense to ME haha!

T bar is in red, figure 1 is from above connecting chassis and swing arm, figure 2 is from behind showing the T bar swivel and how it can be controlled with springs and bump stops, figure 3 is from the side showing how the motor mounts atop the swingarm pivot.


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## dain254 (Oct 8, 2015)

I've been slowly working on an updated design of a mini buggy I built a couple years ago - my goal is to create plans that will allow it to be built in gas or electric. From what you have described in your previous posts it is exactly what you are looking for. It could be built with many different motor/controller options and can fit 2-8kwh of Chevy Volt batteries either in a 50.4V or 100.8V setup. The first one I build will likely run 4kwh and 100.8V to keep it light and fast - and use a Motenergy ME1507 and a Kelly 96601 600A controller. That setup should give me 40-50hp easily and be overkill for power. Based on a couple of my other projects 4kwh should power it for a half hour minimum, or about 15 miles. We have a car show at work every year that I build something new for... so I will have it completed by August. Attached a pic of my CAD model for updated and a pic of the completed fuel powered variant, with only a 13hp engine it works great!


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## dain254 (Oct 8, 2015)

I should also mention that weight will play a big factor in your performance as well - utilizing racing ATV suspension parts helps keep weight down for a 1 off build, but for something that the masses can reproduce in their garage I will be using off the shelf, heavier components for front suspension and will go to a 1.25" OD .120 wall tubing instead of the 1" .095 and have eliminated all of the bends. The fuel version weighs in a tick under 380lbs and I expect the electric to be around 425lbs.


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## Jonbickford (Feb 27, 2018)

yes, very much like that!! do you have any other pics of the chassis, how the engine connects in back and that looks like a single a arm in the CAD but you went with double on the front in real life?

VERY cool! pretty much that but with the feet behind the axle and side pods to carry batteries.

at 72v/72ah I'm looking at 5.1 kWh for 96lbs of battery which seems like a real decent set up. 60 lbs for the HPEVS ac motor should make 42.6hp and 106.8 lb/ft which should definitely be enough to fly!

where are you located? let's race! haha


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## dain254 (Oct 8, 2015)

Located in Iowa, would certainly be down for a race! 

The CAD model of front suspension is not complete - I am still designing the front spindles and upper control arm, the lower arm that is in the image is the correct arm. The rear swingarm is completely custom made to withstand the torsion of cornering within the swingarm itself, on hard cornering the buggy will actually carry the inside rear tire if it is gripping hard and not drifting. The jackshaft is mounted underneith the engine at the point where the rear swingarm pivots so the chain does not change tension through its travel. The design allows for the electric motor to be mounted on the same axis where the jackshaft would be, and the chain is tensioned by threaded heim joints that connect the swingarm to the chassis. 

As I'm sure everyone will tell you on this forum as well, the amount of power is directly proportional to how much money you will need to spend to make it, and sometimes becoming exponential. To do a 25-30hp setup for a vehicle like this including a 3kwh Chevy Volt Lithium Module could be done for about $1200 assuming you are buying the Volt modules at pack level prices which is about $85/kwh (I just buy complete Volt packs when I need more). A Motenergy ME1003 brushed DC motor and 72V 400-500A controller along with pedal and things like that would get you moving nicely. 42hp on your ideal setup would be plenty, and I plan with my setup to be able to wheelie on command


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## Jonbickford (Feb 27, 2018)

That does sound almost exactly like what I’m thinking! Putting the motor in line with the swing arm between the two mounting points is my most likely scenario as well. I will probably use pretty heavy tubing from the get go so I can bounce off rocks in the desert...

I am Interested in the Montenegy motors as well, I know more about hpevs ac motors and they seem comparable in price a little more expensive for motenergy kits though the motors seem to be a good bit lighter.


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## Jonbickford (Feb 27, 2018)

My car will be in California but perhaps some time a grudge match can be arranged! Haha

I’m leaning towards CALB cells, they will cost more than going with Chevy packs but can be bought new and packaged the way I want in simple to remove boxes.


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## brian_ (Feb 7, 2017)

dain254 said:


> The rear swingarm is completely custom made to withstand the torsion of cornering within the swingarm itself, on hard cornering the buggy will actually carry the inside rear tire if it is gripping hard and not drifting.d


A non-articulating rear suspension has very high roll stiffness (not infinite only because of the tires), while the articulated front allows roll, so inevitably almost all of the lateral load transfer will occur at the rear, to the point of the inside rear tire lifting if there is enough lateral acceleration. It also means that in a corner the outside rear tire gets most of the traction - at the expense of the inside rear tire - which is a good combination with rear wheel drive, no differential, and a loose surface.


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## brian_ (Feb 7, 2017)

Sorry for the slow response on the suspension idea - I've been a little sidetracked and wanted to think about this...


Jonbickford said:


> I don't know what it is actually called so I'm calling it a T bar.
> 
> picture an atv style swingarm, this is attached at the pivot to a T shaped component, the lower part of the T is laid down on the centerline of the chassis and held with bushings. the T is allowed to swivel side to side say, 22 degrees or so, this lets the swingarm move side to side. unlike a ball joint and triangle to the axle design the T bar doesn't need any other assistance keeping the rear wheels pointed straight ahead.
> ...
> ...


One way to think of this is articulating the chassis on the longitudinal axis, and using a simple swingarm on the rear chassis section. I think the challenge would be building this to be stiff enough, so that the swingarm doesn't "steer".



Jonbickford said:


> in sand dunes or rock crawling you want as much articulation as possible but then you're dealing with body roll in corners on a grippy surface, I started thinking about how a sway bar would work and decided I could use sway springs instead... if the T bar has a tab sticking up on the center shaft you can put walls on either side of that tab and use adjustable bump stops to control just how much side to side travel you have, but you can also place springs on either side of the tab that would act as anti-roll control... stiffer springs create more roll resistance and does it completely independently from the up and down motion of the swing arm! that way a softer more compliant spring rate can be used at the swing arm and body roll is completely separate, the 2 shocks would still absorb motion side to side in a dampened way so the roll springs wouldn't feel harsh or bouncy I don't think.


The roll (or "sway") spring only affect roll motion, as with any stabilizer bar. If I understand correctly, the two shocks are to have coil springs on them, to support the vertical load. That means that they also resist roll, as with any conventional suspension if you removed the roll springs, the whole suspension would still not roll freely. Although you can exert roll control with the pair of springs at the T-bar, or with a torsion bar along the centreline controlling the T-bar, you can also use a conventional stabilizer bar.

I don't see a problem using just the two shocks to control the suspension in both rotations... that's what most suspensions do.


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## Jonbickford (Feb 27, 2018)

the primary coil over shocks would be handling movement in both directions, but in the interest of having a longish suspension travel of around 10" I would like the springs to be pretty compliant so they aren't chattering your teeth out. but with that much travel on soft springs body roll will be pretty bad in some circumstances and a roll control separate from the soft spring rates would be necessary to have both a grippy compliant ride and level cornering ability. it would be a fun thing to play with. the t bar springs would be doing what a sway bar does but maybe with less harshness and more adjustability. chances are I'm just going to go with a solid swing arm design but I would want to experiment with this some time after the car is up and going.


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## dain254 (Oct 8, 2015)

The bushings that connect the swingarm on my buggy are rubber - so it has a little flex between that, itself, and the chassis. It also makes for easy power transferring when a person doesn't have to worry about that added dimension of movement. I've considered making it articulating... mounting the jackshaft to it and using the belt CVT to take up the difference so the chain doesn't have to twist... but at the end of the day the driving experience of the machine is much more fun with it rigid. Here is a quick video of a buddy of mine driving it - he was afraid to leave the ground  

https://www.youtube.com/watch?v=Sz5qe88vjJw


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## Jonbickford (Feb 27, 2018)

that's awesome! there's a lot of videos out there of swing arm buggies really getting pushed hard it definitely seems like the best bang for $/weight. I guess the low air pressure high sidewall atv tires take out a lot of high frequency vibration as well.

after your buggy video it went to a powered parachute video no THAT is fun!!! I took a lesson on a 2 seat pegasus a few years ago so great! I definitely want to get into that in the future!


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## brian_ (Feb 7, 2017)

Jonbickford said:


> the primary coil over shocks would be handling movement in both directions, but in the interest of having a longish suspension travel of around 10" I would like the springs to be pretty compliant so they aren't chattering your teeth out.


Classic off-road suspension consideration.



Jonbickford said:


> ... but with that much travel on soft springs body roll will be pretty bad in some circumstances and a roll control separate from the soft spring rates would be necessary to have both a grippy compliant ride and level cornering ability.


This is why most automotive suspensions have a stabilizer bar (or "swaybar") separate from the springs. Recent race suspensions (such as in Formula 1) even have three-spring arrangements, with one (called the "third element") handing collective motion, and the other two handling individual wheel motions, while there is still a stabilizer bar for roll control.



Jonbickford said:


> the t bar springs would be doing what a sway bar does but maybe with less harshness and more adjustability.


I don't see why it would be any less harsh. Conventional stabilizer bars are very adjustable, by changing the position of the end link on the bar end.



Jonbickford said:


> ... it would be a fun thing to play with.
> ...
> chances are I'm just going to go with a solid swing arm design but I would want to experiment with this some time after the car is up and going.


This is one advantage of off-road vehicles - you can play with designs and not need to ensure that each version is suitable for public road use.


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## dain254 (Oct 8, 2015)

Jon - the powered parachute video is my Dad flying his own machine for the first time after he took training - I shot the video from my electric UTV!


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## Jonbickford (Feb 27, 2018)

Brian, the 3rd spring in formula one and indycars is where the idea came for the anti roll springs on the t-bar! not exactly an Adrian Newey car though...

I was thinking I could use large ammo boxes as the shells for my battery packs, it's almost the perfect size for 12 calb 72 cells with a nice size air gap in-between and a bms I think. You could even stuff 15 cells into one of them for 48v packs but I am still wanting to keep weight and cost down... how much airflow would I have to create through the box to keep batteries from over heating? could I just get away with some louvers or would I want to have a fan or two to pull air through? any chance I could leave them sealed up and weather proof?

that powered parachute was SO cool! we took off and I took the controls at altitude and flew around the valley for awhile no problem, when we got back to his dirt field he asked if I get motion sickness, then we spent about 20 minutes doing touch and gos, corkscrews, flying right on the deck, he said he would follow his dirt bike friends right over the trails and pull up to clear oncoming traffic! it was awesome! the really cool part is that you're never going over about 45mph so unless you have a total chute failure they are pretty survivable! as my instructor said you will probably survive the slow crash but maybe not falling out of the tree afterwards! lol


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## Jonbickford (Feb 27, 2018)

I saw this buggy pop up on Craigslist with a dual chain rear suspension design, the add says it is a roketa but I haven’t been able to find another one like it yet.


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## Jonbickford (Feb 27, 2018)

so it's a roketa gk-33 for the single seater, found more pics of the dual chain design.


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## Jonbickford (Feb 27, 2018)

it says it's a single speed forward and reverse, so I'm guessing cvt and this box on the back changes forward and reverse? can't tell how the engine connects.


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## brian_ (Feb 7, 2017)

Among the Roketa buggies for which http://www.roketapartsdept.com shows parts (which strangely does _not_ include the GK-33), several have trailing arm independent suspensions, and the GK-13 and GK-29 have dual chains (the rest have jointed shafts). The parts listings give a good indication of what bits are needed; although I haven't sorted through all of the transmission pieces, it looks like they use a Reverse Gearbox (part 23 in the Engine/Exhaust Parts for the GK-13; part 10 for the GK-29), separate from the engine and CVT assembly (part 24-08 for the GK-13; part 21-01 for the GK-29).



Jonbickford said:


> it says it's a single speed forward and reverse, so I'm guessing cvt and this box on the back changes forward and reverse? can't tell how the engine connects.


I assume that the photo shows the Reverse Gearbox, which is inline with the CVT output, which is ahead of the engine. Logically, a motor could sit where the engine does, with chain drive instead of the CVT, and the reversing gearbox used only if the chosen motor doesn't reverse readily.


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## Jonbickford (Feb 27, 2018)

BIG NEWS! 

I bought a chassis today! it is a triple E stadium superlites chassis from the early 90's, the class they used to race in the mickey Thompson stadium races! the seller estimated around 450 lbs with the 460cc 2 stroke engine that is in it. I didn't believe him at first but I can lift the front axle far off the ground gripping it with one hand, I can lift the rear axle a couple inches off of the ground by myself as well so it is VERY light (it's a superlite after all) it has a differential and transmission, it's hard to climb into but once inside it is very comfortable and roomy considering it's size. it has enough room behind the seat to fit the motor and all the batteries I want to carry and since it's an offroad race car it should be plenty strong enough to handle the weight.

I also got a great deal on it that puts me under budget which means more power! I'm not crazy about the lack of front brakes but that can be adapted down the line. 

when I originally started on this concept the thought was, "something like the superlite buggies they used to run in the mickey Thompson series" as it turns out it actually IS a stadium superlite that I am adapting! 

it won't fit in the bed of a truck, but other than that it's just fantastic and I can't wait to start wrenching!


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## Jonbickford (Feb 27, 2018)

here it is home safe! this superlite is already awesome with the 460cc 2 stroke engine. it will be a complete riot with electric torque and a lower center of gravity! 

it's 6'3" wide at the rear tires and has a 6'6" wheelbase so it's basically a square footprint with a differential so it ought to corner like a beast!


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## Jonbickford (Feb 27, 2018)

More big news on the build, the motor kit has been purchased, go big or go home. HyPer9


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