Go Fast

[makaveliks]

I decided to build a go fast toy. I had this HPI Mini Trophy lying around. I hate it. It's very reliable, with the traxxas 550 it goes faster than it can handle and never broke anything. But the steering is horrible, it has no suspension and drags itself around banging off whatever is on the ground spinning it's tires and rolling over every 5 seconds.

So I took it apart. I separated what I liked from what I didn't and came up with this. The like pile is the tiny pile next to the yellow truck. The rest is the garbage pile.





So then brainstorming happens. I brainstorm with aluminum. I liked the layout, but 4wd seemed dumb to me. I'm not going to use this much because it's fast and I don't like to go fast. I'm also not a person to do things how there usually done. So this truck will be a buggy. And I was originally thinking independant suspension, but these dogbones don't give you much to play with, so next on my list is casting a solid rear axle housing for the HPI bits. If it breaks, no big deal I can cast another and swap parts quick. This buggy will not be too scale like my last one, but it will be realistic looking. I'm not modeling after anything in particular. Just going to make my own design of a cool looking buggy with trophy truck style suspension. Why not? This one is just for fun, and even if it isn't the greatest, building it will be more fun than keeping the HPI on the shelf!

[makaveliks]

Axle is molded. First I cut apart the rear knuckles on my bandsaw. Then I used them and the diff, and made a clay piece to go in between. This was to give room for internals.





Once this was done I put clay over it and sculpted it into a horribly ugly axle casing half. Once that was cooked, I put the internals in to check fit and then added more clay inside where I felt appropriate. This way when I cast a plastic one it'll be beefy. Hopefully beefy enough to survive.

After the first half was done, I put clay in over where space was needed for moving parts. Then used the other diff and clay to sculpt the rear casing. Once both casings done, I took them apart and threw some mold putty on the exterior. When that cured I sprayed some mold release over it and put mold putty over the internals. Now it's curing. This used the last of my mold putty. No more casting parts for a while until I fit more into my budget. It likely won't be hard enough to demold tonight. Tomorrow I plan to cast the new casings. Then I'll spray some paint on them and show you how horribly ugly they are. Sure, I could have made them look ok, but with that huge diff, and need to be beefy to hopefully survive, there was no point. So I made it fun! LOL


Here's the molds curing...

[makaveliks]

Here's the ugly clay buck and the molds ready to be poured! Should look sweet for such an ugly thing!

[makaveliks]

I came up with a theme... UGLY! This is gonna be that bad ass you see at the bar and don't make eye contact with!

So today was time to get the axle cast! I started by bending up these .071" 6061-T6 aluminum tabs which will be my link mounts. I bent like this so I could have a maximum amount bonded into the resin so they don't come loose!




Next I warmed the molds in the oven at 170 degrees for about 10 min, then used Alumalite Performance 80D resin to cast them. I do not have a vacuum chamber to debulk the resin so it's got lots of air bubbles!




Then I painted the outside of the axles, and left the insides bare. Then the axles needed to be built! I pressed in the bearings for the input on the diff, then put the diff in. Once this was in I just needed needed to pop in the dogbones and outputs. What you don't know is that I made the width a little wider than it originally was. So to keep the dogbones centered so they wouldn't pop out I used these o-rings that I have been pulling out of my RC4WD scale shocks for years! They finally have a use! They'll also quite the dogbones down.





Then using a 1/8" drill bit in my dremil I machined out the recesses nice and smooth for the screws and nuts that hold this together. I put a very thin bead of shoe goo along the mating surfaces of the axle. I did this for 2 reasons. 1, to hold it in place while I drilled it. 2, to make sure it's sealed. It's thin so if it needs to come apart shouldn't be to much trouble. Then I drilled my screw holes and screwed this sucker together! Now I have an ugly solid axle from independent suspension parts!





Last I made up some quick ugly rear suspension lower links. They are made from scrap left over from my FJ! they are 1/4" 6061-T6 for the main body, and the plates that act as shock mounts are .071" 6061-T6. They are long! I might be overdoing the suspension... O well, it'll be fun! I also bolted in my 110mm RC4WD King shocks. I need to make up the front suspension, then get everything mounted so I can work on my shock mounts!

[rustneversleeps]

Hey man thanks for the thread.Looks like a go fast TT cool .one of a kind great job.....

[penneyma79]

Like it! Have some set of brass ones to make your own, very cool! Looks beefy.

Sent from my SCH-I545 using Tapatalk

[makaveliks]

My wheels/tires came in the mail. Got them mounted up. pin mount has a bigger ridge than original hex. Seems to pinch the bearings. I'll need to grind this ridge down a little to be about as wide as original I think. Tightening nuts as it is and the wheels don't roll well...






The rear is super close to the trailing arm. I may need to turn wheel inside out. It'll look cooler that way anyway I think. We will see when I get this all together and can see if it rubs.




But all that is just small peanuts. I can mess with on final assembly. I need to build stuff! So the big task for today was getting the front suspension made. I can see how everything sits so I can make the back to kinda be similar. Don't want 10 inches rear travel and 1 up front. That would be goofy!

So first step was to make some c's. Originally it just had ball ends in the end of the arms that mounted in the hubs. This obviously limited travel to the range of motion of the ball end. So I made some c's from 10mm delrin plate. These will allow the hubs to turn and allow me to hinge the arms so they have a bigger range of motion.

Then I made the arms. I made the upper out of 7mm plate, and the lowers out of 10mm. Wanted them beefy. I used the original pins from the HPI to hinge them to the mounts, and 3mm screws everywhere else. I'll need to make some plate to screw over the poins to hold them in place. I hate fiddling with e clips, and want to make this user friendly since I am the user. LOL

Last was the mount and shock tower. This is prettymuch solid. I just stacked the 10mm delrin and screwed it together with long 3mm screws and sanded the layers and used shoe goo between the layers. This is as good as one piece. It's ugly. Goes good with the rest of the build!

In the end the front is 10 inches wide, and has about 2 3/4" travel. And this is with 110mm shocks. I probably could have gotten it over 3 by making the arms closer in the center, but then it would need more support, and I could have gotten a little longer arms on the other end if I made shorter c's, but that would limit steering. So I felt this was the best compromise of maximum steering, travel, and strength. Also, if this were a 10th scale trophy truck it would actually be right on the scale money... So now when I do that back, I'm going to try to keep it near 5".

It has too much camber. I only made the upper arms 5mm shorter, figured it would help in turns, but seeing the actual stance, it's ridiculous. Tomorrow I'm going to cut the upper arms in half and make them adjustable so I can put my camber where I want it.

[makaveliks]

First today I ground down the hubs. Now the wheels spin freely!




Next, I wanted to get the rear arms mounted.




After those were mounted I mounted my motor/transmission so I can see where I have room for my upper links. There wasn't much... I ended up making them really short. It looks like it works well though. As the axle swings up and down it also rotates and keep the driveshaft lined up well. I'm sure there's something bad that will come from it that I'll find out when I drive it, but I'll go with this and see what happens. Without moving the motor either to the center or further forward it's really the only option. I would normally move things to make it ideal, but with this being so small, using big motor/battery this wasn't much of an option to keep the center of gravity low.

I also cut my front upper arms and threaded in a long set screw to make them adjustable. Fixed the camber issue, and now I can mess with it if I want to change it at all.

Next I'll need to do the rear shock mounts and steering.

Here the front is all the way up, and the rear is on the ground.





Here it is all the way up. It obviously wouldn't be able to drive like this because the shaft is almost at a 90 degree angle from the transmission. So somewhere in between is where I will have to limit it.




This is about where I expect to have when resting.




Here's the front end. The camber is much better. The one on the right might need a little adjustment still.





And here you can see where I cut the arms to put set screws in.

[makaveliks]

Got the rear shocks mounted. Just made a quick aluminum shock tower. I think I may flip the lower arms around to push the shock mount further out toward the axle. This will limit it a little more. Right now it's super soft too. This should stiffen it slightly, but I also have other springs, and the adjustable shock bodies too to play with. I won't worry about tuning them right now though. I'll wait until it's got all it's weight.

[makaveliks]

Don't have time for pics today... I did get the steering done, might need some tweaking. I just made a simply delrin servo arm to hold both steering links. Links are like all others and just 3/16 aluminum rod drilled and tapped with long set screws and plastic RC4WD links. I got it running. I found a couple wierd things.

1st is the way the rear axle swings, the torque makes the rear of chassis go up and pushes axle down. So when using any throttle the rear goes in the air, all weight goes to front tires, rear has very little traction. So I'll need to fix this by making new rear links near length to the lowers. I'll probably first try to use my rear shock tower for a mount and see how that goes.

Other problem is the rear end itself. I when I get on the throttle the rear gears skip. I've been shimming it a little at a time for the last hour and it's getting better. I'll try and do some more tomorrow. If the rear end is not holding it's shape under throttle and this problem doesn't go away, this will go on hold until I can just get a new axle. I can't imagine this thick stuff is moving that much and not breaking... Hopefully it's just my casting process left some play between the housings which I can't see without xray vision. We will see after some more shimming.

[makaveliks]

So here's some pictures and a video. The video shows the problems I had with the original rear suspension.

This is my steering. You can see it's 2 simple links and a delrin block I cut and screwed onto an existing servo arm to hold the 2 link ends.




The servo is just mounted to 2 delrin blocks and screwed to chassis.



Then once it all worked I took it outside and gave it a test run! I took it really easy, hit top speed(nothing crazy because I put a 10t pinion, original was 18, in to keep electronics cool), hit some small bumps. This video shows all the problems I had. Shows, the rear end lifting when I hit throttle, dropping when it hits the brakes, and then the rear end skipping gears at the end.




These problems obviously needed to be fixed if It was gonna be worth continuing to build. First I tried shimming the bearings int he rear end, problem with gears did not go away, just took more throttle to make it happen. I think the plastic was flexing and letting the mesh change and gears skip.

What I did was take the rear end apart, grind out the forward casing to fit the original front diff cover inside it. I figured the back half is pretty solid, and the front with the input shaft most likely has the play. Once it was ground out, I JB Welded the original cover into the front cover. I did this so hopefully strength in the casing does not drop too much. The rear of the housing is then screwed onto it like the original back cover, and all the screws I put the axle casings together are also installed. Seems to work great now!


The other part was the links. I looked up some link set up stuff online and found out you need to figure out instant center, cg, and some other things, and then eyeballed some new better looking angles. I used the rear shock towers for mount locations. The motor was kind of in the way for the passenger side link so I had to bend it to look kind of funny.

Took it for another test run and it now runs great! The rear end is completely neutral! it does not go up or down, and there is no noticeable torque roll! I don't know how I managed that, but I guess I got lucky! It could also be since I'm running the paddles on a harder surface right now...










So now I need to do some fine adjustments to the front and get a video of it running in the daytime. After that it will all be down to making it look cool.

[makaveliks]

Slight changes for today. I adjusted the front camber, installed the new bearing, and, I made some new shock mount plates for the rear links. Just did this to shorten them so the tires don't rub, and adjust the shock mount position for a little more travel. Because of this to let the shocks bottom out when the chassis does I had to move the upper link mount back to the original position. Seems to run great. Will need spring adjustment and probably some different shock oil when done, but until I get the body built with all the extra weight it's not worth messing with that now.




And here's the video of it running. Much better.

[makaveliks]

Not a big update... I've been debating what I want to do next. I came up with a way to increase travel using same shocks. To do this, I'd need to make some more parts, not a big deal, and then make more parts for the steering to also increase it's travel because suspension cannot drop more without the steering going with it.

Either that or just move on... LOL I might just move on.

But my 2.2 RC4WD steelies and paddles came in, so I got them mounted up. They'll fit the look much better. Bigger so truck will have a little more speed and clearance, and it will look more the rat rod look with being larger than the front.

[makaveliks]

Today I began messing with the front again. I decided I wanted more travel. I know it doesn't handling, yada yada yada.... But if nothing else, it'll look cool banging around!

I was thinking of using an arm and a link to essentially make a movable upper shock mount that moved with the suspension allowing the shock more travel than it really had. So the first step was to remove the shock, move it inboard to make room for my link which was going to go where the shock was mounted. In doing this and clearing out room on the arm for the shock to fit I had found that my suspension arms are at the perfect angle. Just moving the shock inboard and using the original upper mount The upper travel has not changed, it still allows chassis to bottom out, but give more down travel.

One side is done. I'll need to do the other, then redo my steering setup to allow this. Now the front has right around 3 inches travel, maybe a little over. In the below picture the buggy is on a 4" box and the suspension is at full droop. The rear tires are touching the table top, and the front are a little under an inch from touching. The angle of the arms looks like about all I'll be able to reasonably get from them.




This pic I'm not holding up the tires, I'm just holding them straight. The right side is the one I just fiddled with, and the left is how it was before.

[makaveliks]

I figured an easy to get my steering to work with the higher angle, so I got that taken care of before before modifying the second side.

To get it working I put a 45 degree ball end on the wheel side of the steering rods. This ends up with the ball end hitting it's limit both when compressed and drooping but with the suspension hitting it's limit at the same time.

The other part of it was my servo arm. When turning at all and at full droop the arms were hitting the body of the servo arm. To eliminate this I made a new one. I used a regular servo arm and made an aluminum t for the end of it. The aluminum t is screwed to the servo arm and the links bolted to that. I also moved the holes on the t about 10mm closer. Now when the arm spins there is nothing in the way of the links.




So here's one side done, the other still needs to be modified.




So I haven't completely decided on a paint scheme yet... I could go quite a few ways with it. I have a lot of vendor stickers I have been wanting to use so I might go more of a racing theme, I may paint it flat black with a mouth and teeth and some kind of nickname on the door, or old and rusty looking.

This is going to be what I'm going to be shooting for with the body but I'll put a hood on it:



This is how my rear end is, and I'll build the tubing and rack for spare tires. It will have the bedsides from the above picture on it.



And this is the type of front end suspension I have. Now you should have an idea of how I'm mixing the 3 types of vehicles together.

[makaveliks]

Today I did a little more work on this. It took me a while, but I came up with a plan. First I decided to make the biggest pieces that the rest of the cage will integrate with. These pieces will stiffen the chassis so they go end to end. It will have more in between to tie everything together and finish the overall design. Each of the side rails have 3 mounts to the chassis.

[makaveliks]

Today I finished my cage. It was a pain. I built the cage drilling and tapping some parts, then others using wire like my last FJ45 pickup, and I used a combination of 1/4" rod and 3/16" rod so in some places I could drill the 1/4" and just put the 3/16" through it. This way I could removed the cage and it would stay together, but without drilling and tapping everything.

Then I brazed it all together. I was going to do a little triangulation in the back between the 2 diagonal bars that run from the cab roof to the back of the bed, but I had put off lunch and needed a snickers and didn't realize until I snapped my 1/16 drill bit. I didn't feel like driving 2hrs round trip to town to get a bit so I skipped that. The rest is done, I'm happy.

During the brazing I tried using brazing rod that I have used before that melts at a very close temp to the aluminum melt. It has a really strong bond. But on the first joint I melted the front drivers side lower corner of the windshield area. So I remade the sections I melted in half and just used my lower temp, softer, not as strong stuff. I kept a cooler full of water nearby and as soon as I was done brazing I kept moving the torch all over the cage to try and make sure it was all hot, then dunked it in the water to quench it. After this I stuck it in my oven at 400 degrees for an hour. This was an effort to heat treat and artificial age the aluminum to try and get some temper back. When brazing temper goes bye bye. It seems to have worked. While I am sure it is not quite T6, and likely not even, it does seem much stronger than aluminum rod I've brazed before.

Next I'll make the body panels. I've again changed the overall plan. Still going for rat rod, but instead of an actual rat rod, I figured I'd go more of a racing theme and just like the race cars I'll make a removable hood/door panel and a separate roof panel. I'm doing this for ease of fabrication and strength it will add to the cage.

[makaveliks]

I got the hardest panel made. The front end! I made a paper template, then traced it on to .025" aluminum, cut it out, formed it over the body, drilled, tapped the rod behind it, and BAM! The rest should go a little quicker... Except maybe the one in the front. The grill might be tricky, but the roof and bedsides will be super easy. This will need 2 more mounts right behind the steering links and some minor trimming. I'll take care of those things after the rest is made and I take it apart for paint. I don't think I'm gonna worry about making small panels to block the openings around the front of this panel. Maybe if I wanted to get crazy, but this is for fun and will take some beatings so I'm not going to waste my time on them. Who knows how many crashes this will even take... LOL

[W1ck3d0n3]

Ok this is goin to look sick as hell if what i see is what u see.

[makaveliks]

I don't know what you see, but I think the same thing... LOL