Full Suspension Big Block Mini-Buggy Build

SquidBonez

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Finally got to work on the buggy again after a few weeks of being busy/bad weather and I got the roll cage on. Still needs more gusseting/reinforcement but it has already survived a small drop test with no damage. It is also surprisingly easy to get in and out of the buggy with the seat in place, which was a concern of mine. Little by little it's all coming together.
 

SquidBonez

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I've been picking away at this project little by little. I decided to cut all the tabs off the floor so I can just weld in a solid floor across the bottom instead. Also did some reinforcement to the main cage. My new rear axle came in, and I decided to set the rear track width to 55" (with the tires installed). So I bought a new 50" axle, cut it down to 45"", and welded the one wheel hub directly to the axle. This is how The Edge Products sells their axles, so I'm confident this will be fine. The other hub is still removable so I can still replace bearings/hubs/rotors if need be. The rear tires are 10" wide and are on centered rims, so each tire sticks out 5" off the axle.
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SquidBonez

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Today I made new spindles (with shorter spindle arms) and made yet another set of a-arms to match the wider width. These arms will move the spindle back slightly and shorten the overall wheelbase by 1.5". Also used square tube this time just because it's easier to work with. Still need to add shock mounts and reinforcements to the lower arms, but the upper arms are done. Looking forward to seeing how this suspension works on the buggy.
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SquidBonez

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Got the lower arms done minus shock mounts. Did a quick mock up with the tires on. Really liking the look of the double a-arms!
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Also got the steering connected with my new spindles. The tie rods going from the linkage to the spindles are temporary (they bind fairly quickly, going to be making some custom ones). Check out that full lock angle!
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There is still some pretty noticeable bump steer but it's far better than it was with the single a-arm setup. Plus I believe that with the new tie rods I'm making I can tune a lot of the bumpsteer it currently has out. By the time I'm done it should be negligible. Also double checked all my measurements and they line up perfectly. Front track width is exactly where I want it (53"). As for the rear I was aiming for 55" but with the tires on it's actually 56"...obviously not the end of the world. Just wanted it somewhere over 50" and under 60".
 

SquidBonez

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Had a little time to work on the buggy today. Just got the new tie rods done. Not only do they not bind at all like the old ones, but the bumpsteer has been reduced to a negligible amount. Now it's just a matter of doing the shock mounts and then the front suspension is done.
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madprofessor

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Only just now ocurred to me................That wig-wag steering linkage to the tierods could have saved me a ton of work when I accidentally built a rack and pinion backwards. Ended up cutting it all off and starting over, wig-wag would have been so much easier.
 

SquidBonez

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Only just now ocurred to me................That wig-wag steering linkage to the tierods could have saved me a ton of work when I accidentally built a rack and pinion backwards. Ended up cutting it all off and starting over, wig-wag would have been so much easier.
To be fair it wasn't my idea, but it works great. A lot lighter and cheaper than a rack, plus it's tunable. Can be made to any size you like. Snowmobiles have a very similar setup.
 

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Sorry for the slow progress recently, just know this project hasn't been abandoned. I'm itching to get back to it but I have been busy for a month with work and other things. I'm adding another bracket for the other side of the upper a-arm as the single bracket flexes easily. I've also been toying with the suspension a bit, I'm now looking at a little less travel (a bit over 4" all around) but I will lower the ride height. Even with the engine elevated 9" from the bottom of the frame, this thing should be very stable thanks to the 56" width and lower ride height. Aiming for about 350 pounds completed which will give me a power to weight ratio of around 17lbs per horsepower.

I'm also trying to increase the rigidity of the base frame a bit. I was originally going to add side bars for rigidity but I want to keep the cockpit as open and easy to enter/exit as possible. So I drew up a quick sketch on my phone of where I'm planning to add more bars to the main frame instead. The idea is placing an X-brace in the center of the chassis and adding extra gusseting at each corner. What do you think? Pictures below:
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SquidBonez

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Got the torque converter on the engine! Definitely a few bugs to work out. I swapped out the 5/8" jackshaft I originally had for a 3/4" jackshaft. And it's a good thing I did because this engine has a lot of torque. So much so that it's become a bit of a problem for the torque converter backplate. This thing is made of 1/4" steel and it flexes under light revving (I'm talking 3000 - 3500 RPM). So I will need to weld two pieces of 1/4" flat iron on the side to stop it from flexing. Apparently this is an issue with these backplates that are just flat pieces of steel with no additional gusseting. Should be fine after I do this. You may also notice that the driver pulley is on "backwards". This is to make sure the belt does not misalign as it shifts through the ratios. The way GoPowerSports sells these 40 series kits actually cause belt misalignment since the driver pulley pushes the belt towards the engine, while the driven pushes it away. This configuration ensures the belt gets pushed away from the engine by both the driven and the driver and the belt stays aligned at all times.
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Also set a new RPM record for this engine. This is unloaded so I don't want to rev it too high yet, but I got 5770 RPM from just holding the throttle down for maybe half a second. The engine itself is running pretty good as far as I can tell. I'm running high octane ("super") pump gas. It starts after a few pulls and doesn't rip the cord out of my hand like the Predator 420 I had did. I don't even need to crack the throttle to get it running. I talked to GoPowerSports and a few other part suppliers to get an idea of what an engine like this is putting out. All estimates point to around 20 - 21 horsepower and 30 ft-lbs of torque!
 
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SquidBonez

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I noticed some play in the jackshaft when I got done running the motor. Apparently while the lock collars are good at keeping things from sliding out of place, they do not provide clamping force to hold everything tight. So I managed to find a 3/4-16 die that's hex shaped so I can create threads with a wrench or socket. Tough work, but it worked well. Now that it's being held with a collar on one end and a bolt on the other, there's no play at all! 20220623_194549.jpg20220623_194552.jpg
 

SquidBonez

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Weather has been BRUTAL recently. I work outside for work and sweat all day, so when I do come home I'm rarely in the mood to keep sweating in the garage. That and some personal stuff has been holding this build up, but I assure you it is still in the works. As it starts getting cooler this project should move along quicker.

I've decided to go back to the engine-on-swimgarm design for simplicity's sake. Not an ideal design but certainly effective as this is the route most people use. I've already got my measurements done and decided to use some huge 3/4" heim joints as the pivots points for the swingarm. This thing should be plenty strong. I'm also working on a custom gas tank made from a 1 gallon compressed air tank. I will post pictures with the next update.
 
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SquidBonez

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The heat finally let off this weekend so I got the rear swingarm built today.
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Pretty pleased with how it turned out. Of course some reinforcement is in order (especially where the heim joints thread in) but it looks pretty strong. The axle is going to mount 10" back from the front on the swingarm as seen here:
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Here's the full view with the engine in place:
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Next up will most likely be finishing the shock mounts for all the suspension and then reinforcing the CVT plate to stop it from flexing.
 

SquidBonez

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Got the torque converter plate reinforced. Just welded a piece of 1/4" thick angle iron and made a gusset from some 1/4" flat bar. Hopefully this stops the flexing.
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Also welded on the bearing hangers too. I might do another two in the center...not sure yet.
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SquidBonez

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Tested the plate today. On the bright side, the plate isn't flexing anymore which means my reinforcement worked. On the down side, my bearings are shot because the driven pulley is spaced out so far from the bearing. I looked at other 40 series kits that are run this way and found that they have a small piece of tube welded to the plate that brings the bearing closer to the pulley to reduce the amount of stress on the bearings, so I'm going to have to do the same. I'd rather find all this out now rather than later.
 

SquidBonez

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Replaced both bearings and got the new piece of tube welded on. Everything is tight and there's no wobble. If this doesn't work, I'm just going to buy a pre-built kit. But it was worth a try since this piece of tube cost me $5 and a new torque converter kit from eBay costs $200+, so it was worth a try.
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Here's some advice on these 40 series kits: if you ever want to run a Comet 40 series the way I am (with the driver facing inboard to keep belt alignment right through its travel), I reccomend you go for the eBay kits and save yourself the trouble. Just make sure you get the STEEL backplate and not the aluminum one as they are highly prone to snapping. The way the GoPoweSports plates are setup cause belt misalignment as the clutches shift into their higher gear. The 780 kit from GoPowerSports also suffers from this problem. These pulleys aren't made to run both facing outboard like the 30 series pulleys are. The driver and the driven need to be facing OPPOSITE ways (driver inboard, driven outboard or vice versa). Also make sure that if your driven pulley is facing outward, you NEED the yellow reverse-wound spring for it to work correctly, otherwise it will just instantly upshift as soon as the driver engages.
 

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Finished the A-arms today and got the back pivot brackets for the swingarm welded on.
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The A-arms should be plenty strong thanks to all the 1/4" thick flat bar I welded in. They're also surprisingly light despite how heavy they look.
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As it stands now the front will have just shy of 5" of travel (4.8" to be exact) and the rear will have just over 5" (5.2"). The rear might change if I have to fiddle around with the shock position, but I'm confident about it at the moment. All I have to do from here is weld the shock mounts to the frame and then we'll have a roller! I also bolted the swingarm in and it pivots very smoothly on these huge 3/4" heims.

From here we still have the gas tank to make, rear section of the cage, pedals, brakes, brackets for mounting wires/cables/lights/horn (yes, it's going to have a horn), weld in the floor pan, additional gusseting, and then finally paint (which I want to save as a surprise for the end for anyone who actually reads these updates). I'd say we're 65% there at the moment. Most of the "hard" work has been done.
 

SquidBonez

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Please don't paint it red, white, and blue....just a solid color please !

only my opinion....da Flash
I can guarantee it will not be red white and blue lol. The frame will be all one color and the suspension components will be another color. The rims, obviously, are white. So only two colors not including the rims.
 

SquidBonez

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It's officially a roller!
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First impressions: the shocks were VERY soft at first, but luckily these shocks are pre-load adjustable. After cranking them down they're a lot better. There is absolutley no noticeable bumpsteer which is a very pleasant surprise since I was expecting there to be at least a little. One problem is the heim joints; this is about as low as the a-arms can travel before the heim joints reach max angle, so this is as high as the front can go, which means that the front end sits lower than the rear. Normally this isn't an issue, but under full compression the front of the frame hits the ground. To fix this I'm going to swap out the 20" rear tires for some 18" tires of the same brand/tread (Carlisle Turf Savers).
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These are the additions I'm going to add to the frame to strengthen the cage (in blue). The rear cage section will be where the seat belt and gas tank mounts go.
 
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