Mini Buggy Build Log

[jman231994]

Hi everyone,

Bit of an essay sorry but wanted to explain it properly

As some of you may know I have returned from a year of forgetting to come on here and uni, and have now started building a smallish off road buggy inspired by the Taipan from Edge Buggies

For those who haven't seen the Taipan it is a small single seater space frame buggy, designed to take up to a 250cc engine. No suspension, just nice chunky tyres for suspension Though the design lends itself well to a rear swingarm and front a arm suspension, which is one reason I like it so much.

The frame itself is being made from 25mm and 20mm rhs, both 2mm wall, and was designed by me in Autodesk Inventor.....but is basically just a copy of the Taipan. I did my first year of mechanical engineering this year and wanted to see what I could do with what I've learned rather than buying plans ( sorry guys, won't be giving out the cad files out of respect for Edge Buggies business and any liability etc)

I've done some very basic stress analysis on the frame and it seems to be quite strong, with a force roughly equivalent to 2 tonnes pushing on the rollcage only causing an 8mm deflection in one beam, and a few others deflecting slightly less. I'm comfortable that this will still just flex the steel rather than buckle it.

Engine is hopefully going to be a 250cc 4 stroke bike motor, otherwise I already have a 110cc bike motor as backup.

Rear wheels are 22x8x10 quad wheels that I picked up for $12 from the local scrap yard....best score yet And haven't found fronts yet haha

I think that's about it...I'll try to post some pics of where it's at if tapatalk agrees with me (first thread on it lol) Ignore the blow holes every now and then in the pics haha....it's all stick welded and I hadn't got it dialed in right for a few of the earlier welds.....gonna borrow fallenleopards mig to patch them up if she lets me

EDIT: okay tapatalk said no so heres the pics from my computer

Just in case anyone asks, first pic is not my buggy, its an actual Taipan. Pretty much what I'm aiming for.

Also, out of interest, does everyone prefer me using the forums photo uploader or embedded photobucket photos?

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[firemanjim]

Thats a great start. And the way you got tbe pics up now is just fine for me.....


EDIT all you do is hit edit icon, then go advanced. Then upload more pics to same post....

 

[jman231994]

Thats a great start. And the way you got tbe pics up now is just fine for me.....


EDIT all you do is hit edit icon, then go advanced. Then upload more pics to same post....

Yea I did try that and it didnt seem to want to play nice...my computers a bit moody today so maybe thats why

I think I'll just leave it as is, odds are I'll only be posting one or two pics at a time from now on anyway

 

[DMCdesign]

Uh-huh, the taipan. Are you planning to add any suspension to it?

 

[OzFab]

More Pics, can I add these to the original post somehow?

You can add up to 10 pics per post; once the first lot load, simply repeat the process. To add later, edit/go advanced/manage attachments, browse & upload...

No need now, I've done it for you

 

[jman231994]

You can add up to 10 pics per post; once the first lot load, simply repeat the process. To add later, edit/go advanced/manage attachments, browse & upload...

No need now, I've done it for you

Awesome thanks, I'll do that if it arises again....mod powers at work haha

Uh-huh, the taipan. Are you planning to add any suspension to it?

As I said in the original post, nah, not at the moment. Trying to keep costs down and if I went suspension I'd want to use decent shocks which would blow my budget out of the water haha. It's gonna be a bumpy ride I know, but I'll cope for a while

BUT, at the back it will simply be a matter of cutting 4 joints, and then making a swingarm and mounts for rear suspension.....and I wanna tweak the front end in the future anyway so I'll just remodel it to take suspension then

 

[mysteryboy28]

bumpy ride? try dangerous too. cheap used quad shocks on the rear of your buggy (like $40 for a pair of polaris sportsman rear shocks) would be WAY better than not having any suspension at all. having those shocks on the rear absorbs the crazy bouncing effect that may cause you to lose control and crash/flip. the rear shocks really help stabilize the ride!

it is REALLY worth it to do the rear suspension NOW, rather than later. spend $40 on some cheap used quad shocks. your a$$ will be happy you did!

 

[jman231994]

I get where you're coming from but honestly I'm happy with it without suspension for the time being. Rear tyres are rated for 7 psi, so that should absorb a fair bit to start with. And on top of that its going to be running a little 110cc to start with so wont be geared to go quick at all, and will pretty much only be driven on flattish loose gravel. Once I get a 250 I'll at least build a rear swingarm though haha

My problem is that over here in Australia finding that $40 set of polaris shocks is pretty much impossible. Anything I could get in that price range would likely be bent old ones off a chinese quad

Though if I do come across some half decent shocks I will build a rear swingarm....would only take an afternoon to convert over, its just at the moment its either hardtail or half built, so I'm going hardtail

EDIT: Actually, I had a good idea, I'll build it with the swingarm hinges in place and the rear reinforced as if it had a swingarm, and then just weld in struts from the swingarm up as though it were hard tail....then when I find shocks I just cut out the struts and mount up the shocks. Easy as

 

[firemanjim]

Uhhh...... NO...... Build it as a swing arm, with the shock mounts and all. Then make a tube for each side the length of a shock that BOLT in..... A piece of bar and a piece of flat stock welded to each end.... Swap out shocks when you get some, and it goes from hard to soft tail in minutes......

 

[jman231994]

I could, but I'm worried that there would be more force on the mounts than if there were shocks in. That's probably completely wrong but just in my head it seems like there would be excessive strain without the shock to absorb some of the load.

That and I don't know what size the shock end would be, are they more or less a common size?

EDIT...again: I thought it over a bit, your way is so much easier that it's worth it even if there is more force at play.

In that case, I now have some questions haha

Is there any particular angle i should be mounting the shock at?

Have any particularly good ways of mounting the shocks turned up or just straightforward mounts?

And would motorbike shocks work? I have a single rear shock off a ct110(one of a pair)that would be long enough, the matching other one was bent at the scrapyard annoyingly
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[OzFab]

Shocks from a postie bike will probably be too light; when it comes to shocks, the most important measurement is the spring tension or load...

IMO, the best way to mount rear shocks is to have the same angle at both ends; if the angle is equal, the load will be close to equal, meaning that it'll be less likely for either mount to shear

 

[jman231994]

Shocks from a postie bike will probably be too light; when it comes to shocks, the most important measurement is the spring tension or load...

IMO, the best way to mount rear shocks is to have the same angle at both ends; if the angle is equal, the load will be close to equal, meaning that it'll be less likely for either mount to shear

Righto, I might do some rough calculations to work out a good spring tension anyway, and then test the postie bike one to compare.

And what do you mean by the angles are equal?
The angle the shock makes with the part it's mounted to?

Thanks for the help so far


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[OzFab]

And what do you mean by the angles are equal?
The angle the shock makes with the part it's mounted to?

Correct.

If the shocks are mounted to the horizontal swing arm & a vertical frame upright, the angle of the shock should be around 45°. if you have a support bar connected to the base frame to a raised rear extension at a 36° angle (as seen in pic below) then mount the shock at a 18° angle to the swing arm & the support bar. (this is only one example, actual measurements may vary)

If anyone wishes to disagree with my theory, please feel free to do so

 

[jman231994]

Thanks, that makes sense. How you described it is pretty much how the back end will be, so that should carry straight over with a tweak of the angles


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[mysteryboy28]

here's a video of my buddy nearly losing it cuz of a little bump and no shocks. he said it did NOT feel good. lol.

www.youtube.com/watch?v=R8ZfWn1Y0Hk

 

[jman231994]

Yea, I'm not gonna be going over anything that rough until I get a 250 though, mostly loose flat gravel. Once I get a 250 I'll give it a go on sand and will definitely want shocks, at least on the back, maybe all round.

But you guys have swayed me regardless, I'm liking how it will look with a rear swingarm anyway

Did a bit more work on it today, cleaned up a few welds, finished some welds etc. Hopefully start the roll cage tomorrow

 

[jman231994]

Got a decent amount of the roll cage done today, top came out slightly wonky, only a few mil though just enough to annoy me haha

Couple of bits need fixing up where I got the angle a few degrees wrong, I think I'll gusset it too cause of where it is.

I was a bit worried with how the shape was coming out but it turned out alright in the end.
Hopefully get the struts off the back of the cage done tomorrow and some of the front semi aesthetic bits



Edit: Do you guys reckon it would be worth it trying to mount the engine seperate to the swingarm?

I know I'll get much better suspension response that way, but I reckon it would be a pain with how my sprockets are going to be located cause of the bike motor



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[firemanjim]

You can mount the engine stationary, but it will require more fab work. You will w have to use another axle to use as the pivot point of the swingarm,(using heim ends and locking collars to attach), and for the secondary drive sprocket will go on. Secondary drive sprocket will drive the axle sprocket. Doing it that way, you will always have correct chain tension, during full suspension travel.....


And Fabroman is correct..... I would put the rear shocks at a 45° angle. Look at the production karts.... look at the angles.....

 

[jman231994]

Yea I understand how to do it, I'm just not sure if the benefits would be worth the extra work cause I'm going to have to run the chain back then forward to get it around the engine.

Thanks for the explanation anyway haha

I'll go sus out some production karts now too


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[jman231994]

Back struts went on today...was a 35+ degree day so didn't get a whole lot done haha




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