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TT MTA4 S50 conversion

I grew tired of my E-Revo and bought a 6T and converted it and I'm real happy with it. I felt I wanted a MT anyway and spotted a Thunder Tiger MTA4 S50, same as the AE MGT 8.0. Luckily the guy with the S50 was up for a trade so we met up and I switched my ERBE for the S50. Crazy some might say but the ERBE has been shelved since early spring.

Anyway the S50 only had 4 liters through it so it's in pretty good shape. I know that y'all want pics so here goes:

https://lh4.googleusercontent.com/-F...0/DSC_0866.JPG

https://lh6.googleusercontent.com/-X...0/DSC_0867.JPG

https://lh4.googleusercontent.com/-P...0/DSC_0868.JPG

A bit cleaner and with engine, tank, pipe, servos and linkage removed. My youngest son is helping me.
https://lh3.googleusercontent.com/-R...0/DSC_0869.JPG

https://lh4.googleusercontent.com/-a...0/DSC_0870.JPG

https://lh5.googleusercontent.com/-F...0/DSC_0871.JPG

https://lh3.googleusercontent.com/-6...0/DSC_0872.JPG

https://lh3.googleusercontent.com/-k...0/DSC_0873.JPG

FOC and locked in second gear:
https://lh4.googleusercontent.com/-t...0/DSC_0874.JPG

https://lh3.googleusercontent.com/-z...0/DSC_0875.JPG

That's nice indeed, very tidy conversion :yes:

There are a few things on the to-do list:

convert to 17mm hexes and 8mm stubs
other knuckles
new steering servo
new body
new wheels
RPM arms
sort out shocks & springs

I've read that the upper arm mounts can be a weak spot as well as the shock towers. I guess I'll have to wait and see how it holds up to my abuse :) Fullforce RC has the upper mounts on sale right now but spent waaay to much money on RC's this month already.

Destroyed my 6T's rear diff housing, wing, the 5mm alu brace across the chassis along with the carbon fiber shock tower on a really bad landing=really expensive!

That MGT mount of Mike's looks really nice - and the 1717 looks like the right motor for the job.

Very nice!

Sexy! Mike's mount looks great like all his other work!
Looks like a fun one to drive.

What a nice clean simple conversion. It makes me want a MGT again.

Thanks for the comments guys :)

It'll be a slow build as I'm swamped with work right now so most of my spare time is dedicated to my kids.

Anyway, waiting for a Stampede 4x4 radiobox and I got a set of, according to the seller, 7075 alu 17mm hexes in the mail yesterday. Well, they are 17mm but is it 7075 alu and what grade? Made for the MTA4 and were dirt cheap. They do have one major flaw though and that's that they don't have any support for the hole in the center of the rim.

But for $15 shipped I figured I could try them out until I figure out what knuckles and drive shafts to use.

I hope to get some wrench time tonight when the kids are asleep and more pics will be posted of course.

very cool, I love this conversion :yipi:

but I'm a really big fan of the MGT :mdr:

can wait to see a vid

FFRC made great stuff, I had 4 upper mount on mine and they hold just fine all the bash :whip:

have you got a link for the 17mm ??

Of course, here's the ebay auction: http://bit.ly/oUzOMC

Quote:

Originally Posted by j.f.s (Post 413191)

They do have one major flaw though and that's that they don't have any support for the hole in the center of the rim.

If they are made for threaded axles, then that is normal, right?

Sure, but the stub axles aren't threaded apart for the very tip of it. The hexes slide on the 6mm axle and are held in place by a pin. Like on the 14mm Traxxas or HPI axles. I'll take some pics later on to better illustrate what I mean. :)

I think I may have missed your point a bit there Brian. I just assumed that all adapters/hexes has the support for the rim since Axial ships adapters with their rims and those adapters has extra support for the center of the rim. I could buy HPI's E-savage hexes since the flanged nut HPI provides has the support for the rim built in to them.

Quote:

Originally Posted by j.f.s (Post 413208)

I could buy HPI's E-savage hexes since the flanged nut HPI provides has the support for the rim built in to them.

Yes, those are the type of nuts I was thinking would be used with these - since you are using the threads on the axle to hold the wheel on - instead of other hex designs that hold the hex on with the axle nut and then use another nut (17mm) to hold the wheel on.

So you could just buy the HPI nuts and use them with these hexes, right?

Yes, that's what I'll use until I find a set of beefier axle carriers that wont throw off suspension geometry.

A few parts has found their way to my house:
https://lh5.googleusercontent.com/-i...0/DSC_0915.JPG

Notice the Revo knuckle... (more to come on that topic)
https://lh5.googleusercontent.com/-k...0/DSC_0916.JPG

This is what the front of the truck looks like right now:
https://lh6.googleusercontent.com/-g...0/DSC_0917.JPG

Differential complete:
https://lh5.googleusercontent.com/-L...0/DSC_0918.JPG

Some progress has been made!

I mentioned earlier that I would swap out the knuckles for some beefier stuff. I went with the Revo knuckles and LST XXL drive shafts. Thanks for the guides and sharing your knowledge mistercrash!

This alters the suspension geometry a bit. The CC between the pillow balls on the stock knuckles are 35mm (~1.4") and the E-Revo measures 45mm (~1.8"). I can see some bumpsteer going on but it's not too bad. I'll be trying different shims and see if I can tone it down. I'm using Mugen MBX6-T hexes. I cut off 5mm from the a-arms so the axles will sit in the middle of the drive cup. This mod with the 6T hexes adds 50mm (~2") in total width.

https://lh5.googleusercontent.com/-r...0/DSC_0961.JPG

https://lh4.googleusercontent.com/-m...0/DSC_0962.JPG

New hole drilled in the stub axle.
https://lh4.googleusercontent.com/-I...0/DSC_0964.JPG

https://lh3.googleusercontent.com/-H...0/DSC_0963.JPG

https://lh6.googleusercontent.com/-P...0/DSC_0965.JPG

Stock vs mod
https://lh4.googleusercontent.com/-N...0/DSC_0030.JPG

Liqiud RC was clearing out their old GPM parts so I bought the following:
1 ea. AGM1012AF08 Silver Alum. Fr Gear Box Brace - 1pr
1 ea. AGM1012B08 Silver Alum. Fr/Re Gearbox Tightener
1 ea. AGM1013AR08 Silver Alum. rear gear box brace
1 ea. AGM1014A08 Silver Alum. Fr/Re Chassis Mount
1 ea. AGM1331F Blue Alum. Skid Plate W/Steering Mou
1 ea. AGM1331R Blue Alum. Rear Skid Plate - 1pc
1 ea. AGM1048 Blue Alum. bushing Steering Blue

I know GPM doesn't have the best rep (on par with Integy perhaps) but for $25 shipped I couldn't resist. Figured the would be stronger than the stock plastic parts at least.

Ball bearing steering:
https://lh6.googleusercontent.com/-e...0/DSC_1001.JPG

Front differential
https://lh3.googleusercontent.com/-e...0/DSC_0960.JPG

Rear differential:
https://lh6.googleusercontent.com/-p...0/DSC_1000.JPG

GPM vs stock
https://lh5.googleusercontent.com/-3...0/DSC_0032.JPG

https://lh6.googleusercontent.com/-c...0/DSC_0057.JPG

More parts are on the way. Updates will follow. :)

Very interesting!
I have never thought of going to the newer revo knuckles on a Monster GT.
I was just looking at mine today.
Maybe this will be my new project.
Out with the Gmaxx and in with a new improved MGT.

I cant help but notice how similar the MGTs are compared to the emaxx/tmaxx.....like some parts seem identical. Did traxxas or Associated make their truck first?

I like it. :)
Nice looking project.
How does them new turnbuckles handle?

Good looking truck! I know you said the bumpsteer isn't that bad, but you might be able to reduce it some. If you buy the "Hollow Ball" kit for the Revo (part #5355X) you can adjust the height of the rod end of the tie rod in the steering knuckle. It looks like you have the rod end in the center right now, I'd try lowering it so its parallel with the lower arm.

You must get a pretty big increase in camber as the suspension compresses too. Is there any way to raise the upper arm mount at all? If you could, it would definitely help with your bumpsteer issue as the rising camber is the main cause of it.

Quote:

Originally Posted by coolhandcountry (Post 414980)

I like it. :)
Nice looking project.
How does them new turnbuckles handle?

Thanks :smile: I haven't run the truck at all. Hopefully I'll be able to do a test run soon. Won't be much of a test though since we've finally got snow here.

Quote:

Originally Posted by Overdriven (Post 414983)

Thanks for your input! :smile:

Yeah, I've been thinking about the Revo hollow balls but haven't gotten around to order them so thanks for posting the part number and saving me some time!

You're probably right about camber. I haven't paid much attention to any angles at all really other than looking at how much bumpsteer I got. It would probably be possible to raise the mounts but doing so would also raise the shock tower so new mounting points for the shocks would be required. Might be worth looking into though.

I'll try and shoot a video of the suspension articulation once I've set toe and camber.

wow nice work, really !!:yes:

love your catch on the shock

can't wait to see it on a vid :intello:

Looking at the pics I can see the upper arm is pointing up while the lower is horizontal. Now look at the arms like a compass and draw an arc at the ends. As the suspension compresses the upper arm essentially gets shorter faster than the lower, creating the rising camber. Since camber is the knuckle moving in and out from the truck, it always effects toe. Making sure the tie rod is as close to parallel to the lower arm will help, but raising the upper arm mount is the best fix.

Whether or not the issue is bad enough to be bothered is up to you. I don't know much about MGT's but I kinda figured you couldn't get away with just shimming the mounts, that would be too easy! Maybe flipping the mounts over? Just throwing out ideas.

I greatly appreciate the input! Both the rear and the front upper arm mount are bolted directly in the frame. The front ones are mounted in an angle though. I'll take some pictures later on :smile:

Just realized that clicking the images wont show them in the original size so for anyone who wants to zoom in here's the album link: http://bit.ly/s5G5fv

Camber rise can be a good thing, especially on a heavy MT that has quite a bit of body roll, the camber rise will cause the tire to stay more perpendicular to the ground, as a result it maintains a larger contact patch as the chassis rolls away from the inside of the corner.

With camber rise, say you are moving pretty quick and make a hard left turn, the chassis rolls to the right, and the right side (outside) suspension compresses, causing the camber to rise up which keeps the outside tires to stay more perpendicular to the ground, maintaining a larger contact patch and thus more traction in the process, which means you can go faster through the corner.

Now the same situation without camber rise, you make a hard left turn and the chassis rolls to the right, and the right side (outside suspension compresses, the camber doesn't rise and it actually tilts the wheels towards the outside of the corner, greatly reducing the amount of area the tire has in contact with the ground, less contact area means less traction, resulting in the truck wanting to lose grip and push to the outside of the corner. Be it a banked or flat corner on a track or just bashing in a dirt field, camber rise is beneficial to handling in all situations.

Take a look at a 1/8 on road race car (Mugen or Serpent for instance), you'll see that their rear upper suspension links are angled very steeply, high at the hub and low at the chassis, so as they corner the camber rises quickly and keeps as much of those fat rear tires in contact with the ground as possible. Camber rise is very good in on road situations and its just as good in off road situations, it's not something you want to try to get rid of, however you can have too much and there is a fine line between just right and too much, but don't try to eliminate it.

I think your MGT will handle much better than a stock one with the addition of those Revo knuckles, if there weren't anything else factoring in to the handling there, I would say that alone would make a big difference.

Also, as far as being able to adjust camber rise, well that can get a bit confusing. If I remember correctly, changing the camber rise at the knuckle/hub (which would be changing the spacing of the upper and lower arms at the wheel) will not affect the car's roll center, but changing the roll center (distance between the arms upper and lower arms at the chassis vertically, as well as horizontally) will affect the camber rise, while typically very minimally, it does change the camber rise. So if you were to raise or lower the upper arm mounts on the MGT, you would be changing the roll center directly, and the camber rise would be changed as a result of changing the roll center.

I say run with it like it is, my MGT turned like a semi truck (stock knuckles, etc.), I'd imagine yours will handle alot better even if it does have some minor bump steer. And if you want some more info on suspension adjustments, download a copy of the Hudy Off-road & Truggy Set-up Book, tells all about that stuff.

Now, this is why I like the RCM Forums; you get high quality answers :yes:

Krawlin, thanks for an easy to understand explanation. I do have the Hudy book in PDF format so I'll start reading tonight :smile:

Here's a short video. May not tell much but I did notice I had some binding in the rear arms so I fixed that last night.

That damn camera really need great lighting to show it's full potential so there's a bit of noise in the video. 1080p available if played from the tube website.

[YOUTUBE]h8NO4DCWmyA[/YOUTUBE]

Krawlin: I've never had an MGT, I just noticed the geometry had been changed quite a bit with the knuckles and bumpsteer was mentioned. After seeing the video, altering the geometry any further probably wouldn't help things. Good point about roll center btw, got caught up in the other elements and forgot about that aspect of it.

Sorry if I came off as rude in that post, wasn't trying to be or imply that you were supposed to know that. But I agree that any more separation at the suspension arms, or changing the roll center, would not do much good without making quite a few other changes or truly knowing what effects it will have on the truck's handling.

However, I noticed in the video that the front end had very minimal bump steer, in my opinion not enough to be noticeable when driving a truck like this, but the rear seemed to have enough bump steer that it could clearly be seen in the video, and rear bump steer is not good thing, that can cause some very strange handling characteristics.

J.F.S, I would suggest focusing on getting rid of the rear bump steer first, as you can always "drive through" the front bump steer by correcting with the controls, but since you can't steer the rear wheels you can't as effectively correct any strange things the rear end does while driving like you can with the front end. Unfortunately due to your modifications, even if RPM offered their true-track kit (basically converts to a lower H arm and eliminates the toe link) like they have for the Revo and Maxx trucks, it wouldn't really be able to work for you as it would revert back to stock width and geometry, so you'll just have to work on getting the toe link set up right.

Maybe it would it be possible to do a lockout system similar to what the crawler guys do on steering axles in the rear of their crawlers. If all of the planes were correct, you could in theory run a short linkage from the steering arm on the knuckle to one of the now unused shock mounting tabs on the suspension arm. I just roughly mocked this up on my MGT with a short steering linkage from a 1/8 buggy and with the stock MGT knuckle it seems like it could work, I'll actually bolt it up and post a picture soon.

I'd also like to bring up ackerman angle, the MGT is known for having terrible steering geometry, where it will turn the inside wheel to full lock and barely turn the outside wheel, a common fix for this is a longer drag link which spaces the mounting points of the turnbuckles at the drag link farther apart, which greatly helps in getting the outside wheel to turn in more. Obviously you want the wheel on the inside of a corner to turn in more than the outside wheel, but the longer drag link makes the ackerman angle less extreme and more like how it should be.

I am curious as to what the Revo knuckles did to the ackerman angle, if they helped or made things worse. I know you used the stock length aluminum drag link with your steering, but do the Revo knuckles have a longer arm than the MGT knuckles? On my MGT, stock knuckles, I used an OFNA Ultra MBX Comp 1/8 buggy drag link modded to work on the MGT (just drilled a couple holes in the right places), and it improved my ackerman angle quite a bit over stock, and actually helped out on the bump steer.
With the steering at full lock (left or right, take your pick), at the inside wheel I only get very slight toe in (1 degree at the most) at the halfway point in the suspension stroke and as the suspension continues to full bump (full compression) the inside wheel toes back out to where it would be at full droop, and for the outside wheel the exact same thing happens with the wheels still pointing in the same direction, slight toe in at the halfway point, about 1 degree, then at full bump the wheel goes back to where it was at full droop. Again though, this is with a longer than stock drag link, but stock knuckles, so J.F.S's system may work just fine.

When you check for bump steer I would do so throughout the steering range, as this is where it's going to be noticed when driving, and here's why.....

....First, a scenario where bump steer will typically not be noticed when driving -

- Lets say you are going in a straight line, hit a jump, fly through the air and you land with the wheels pointing straight ahead, and you will continue on after the landing in a straight line. As you land, the suspension compresses, now since the suspension is exactly the same on both sides of the truck, both sides do the same thing. If you have bump steer, the wheels on both sides of the truck react the same, be it toeing in or toeing out (or both) throughout the suspension up stroke, but because you are going in a straight line and the suspension is the same on both sides and thus reacts the same, all this bump steer does in a straight line is scrub speed due to the wheels toeing in or out, which is unlikely to be noticed.

Now, two scenarios where bump steer will typically be noticed when driving, both include weight transfer but one is much more extreme than the other-

- Lets say you are about to hit a jump that is just ahead of a corner. You plan to land with your wheels turned slightly after landing the jump. So you hit the jump, fly through the air, and you are approaching flat ground with your wheels turned, ready to dart into the corner. The corner is going to the left, so you land with your wheels pointed at nearly full lock to the left, but it's not a perfect landing, you land first on the front right wheel. Now as soon as the tire touches the ground the suspension starts to react by compressing, and as noted earlier, bump steer occurs and changes throughout the suspension stroke, so as the front right suspension compresses, going through its entire range of motion with the wheels turned to the left, the wheel in this instance will toe out at a pretty extreme angle of 5 degrees, but most of the truck's weight is on that front right corner as it lands, so naturally the front right tire dictates where the truck goes because it has the most traction and largest contact patch at that moment, but it's just toed out at 5 degress because the truck has some pretty bad bump steer and that was the first corner to have it's suspension go through its range of motion. So now even though you are inputting left steering, your steering geometry says no and sends the truck in the direction that the first wheel to make contact with the ground is pointing, which would be more like straight ahead to the mid point of the corner, and the outside barrier of the corner. This means the truck did not react as you wanted it to, it reacted as the steering geometry wanted it to. This is very common in offroad vehicles with bump steer, landing from a jump with the wheels turned and the truck wants to veer away from the corner (in extreme cases), or turn less than the steering angle at full droop.

(See next post, had to edit because the post was actually too long! :tongue: )

Scenario two is much less confusing than my rambling sentences in scenario 1. In scenario two, you are going full speed ahead down a straight away on a track and about to enter a large, high speed sweeping corner, and again the corner goes to the left. Assume you are driving a car with a high center of gravity and soft suspension. As you slow down slightly to enter the corner and begin to input steering, the vehicle (and thus obviously the suspension) react, and you begin to turn through the corner. As soon as you input steering, the suspension reacts from the weight wanting to continue in the same direction, so the weight transfers to the outside (right side of the vehicle) and the chassis rolls (vehicle leans to the outside of the corner). The suspension is reacting to this by the car's left side (inside) suspension drooping and the car's right side (outside) suspension compressing. In this case, the bump steer would be toe out as the suspension compresses. So the as the weight shifts, the suspension reacts as the chassis rolls, and at the same time that the right side (outside) suspension is compressing, the outside front wheel is toeing out. This causes the car to under-steer, as the outside tires have the most traction, and the front outside wheel/tire toes out as a result of the suspension compressing and making bump steer show its dark side. You have to basic walk a fine line between losing it/spinning out and compensating for this bump steer, which is basically over correcting if the bump steer were not there.

So the point of all of that? Well, not much point other than just to spread the knowledge, because really we are just dealing with a monster truck, not an F1 car, and I think the only bump steer you will likely notice any ill effects from would be the rear bump steer, as you can't correct that by direct input to the rear wheels as you go. There are at least 2 digits worth of things you have to factor in here, and trying to make them all right would be like trying to polish a turd, because its just an MT and its suspension and tires are going to be numbing enough to the feel of the truck that you shouldn't notice much difference.

If you so much as adjust the camber on simple geometry pillow ball suspension like the MGT has you can affect bump steer at the same time, as well as camber rise, because you have to lengthen or shorten the arm (threading the pillow ball in or out of the arm counts as changing the length of you arm, as the pillow ball is 1 of the suspension's pivot points), and lengthening or shortening the arm changes the height difference between the upper and lower arm which affects camber rise, and changing the camber will affect the kingpin inclination angle which affects how bump steer changes throughout the suspension stroke at any given steering angle because kingpin inclination angle causes the arm on the knuckle to swing in an arc, which alters the plane of the steering linkage in relation to the lower arm throughout the steering range of motion and suspension's range of motion, etc., and things like this should be given some thought when trying to eliminate bump steer, and realistically unless you can completely redesign the suspension and steering geometry, you may not be able to get rid of all of the bump steer, in many cases though you could work with it as a tuning tool or a driving aide (Remember, bump steer is not always bad).

The simplest way to reduce bump steer to where it does not affect the vehicle or can even be noticed when cycling the suspension on the bench, is to play around with the height of the link at either end, now in the rear you can't adjust that since the bolt goes through the turnbuckle horizontally, but you can change the height of it at the knuckle, and in your setup you can shorten or lengthen the link and change it's mounting point on those CF link mounts you have to fine tune it. I will try out that lockout setup on my MGT now and post a picture later tonight and let you know if it works well on the bench (my MGT is in the roller and for sale stage, can't really run it).

Enough rambling, just thought I would throw some information out there since changes to suspension and steering geometry on our RC cars are often not given the thought that is given to changing the suspension and steering geometry on a 1:1 real vehicle, and 1 change can affect so many other things at the same time and not always in a good way, and even though we aren't dealing with an F1 car, the same things still apply. If you have a question about it, just ask, I'm no expert but I'll try to help as best I can, as I've had alot of experience to say that I've "been there done that", especially with trying to improve suspension/steering geometry, I own two Mugen MBX5 series cars (5R and 5T), so I know all about bump steer issues.

Just some food for thought. :great:

Any updates to this or did I kill the thread with all the suspension/steering geometry talk? :lol:

I think you may have temporarily stunned it.

lol, no worries. Family, weather and a persistent flu has kept me from tinkering with the truck.

I've connected all the electronics and calibrated the ESC to the RX but that's about it. Still have to set the slipper and set the torque control. Then there's the crazy weather preventing driving with rain and storm winds and temps in the 50°F range. We usually have around 20 inches of snow and temps around -4°F from the middle of November.