Testing Chassis Flex On RC10 Buggy Variants

[morrisey0]

So, I got a little something something coming in for my FR01 based car, and the question of chassis flex came up. The ol' question of whether graphite chassis flex much more than aluminum tub chassis. I got to researching a bit, and it just became too bogged down, and too much opinion without facts, blah blah blah. I really just got bored of reading thoughts, and some of them that didn't make sense and contradicted themselves.

So, while sitting in a meeting this morning not paying attention to the meeting at all, I realized that in my office office,I have two basic tools for measuring flex at a rate ............... so I then "borrowed" them and headed home. I now have a force gauge and a dial indicator, neither very nice nor fancy, but enough to conduct base experiments.

So, I want to compare "flex" of various chassis. For this experiment, I want to measure the amount of force required to produce various amounts of movement within different chassis. I want to ultimately compare flex while holding the rear transmission area stationary, and creating various lifting forces at the front body mount hole, and measure movement at the front lip, or location TBD.

I am considering the back portion of the chassis, from behind the bulkhead, to be rigid. But I am looking at the two major differences in chassis to be separate here.

Aluminum tubs depend on the rear bulkhead and transmission for rigidity. The same can be said for the nose plates and nose tubes in the front. The aluminum tub creates it's toughness by effectively transferring forces directly from the nose plate back to the transmission case, and ultimately to the rear of the chassis. So, for any tests on aluminum tub chassis, the nose plate, nose tubes, bulkhead, trans (6 gear case at least), and trans brace will be installed to make sure the original intent is there. The plan is to literally place a clamp on top of the trans brace to hold it solid to the table, and apply upward force at the front.

The flat graphite chassis don't/can't do this. They have to rely on the rigidity of the chassis material itself, as it can't transfer force to anything else. Therefore, for my experiments, I won't have all of these components installed on the flat/graphite chassis. To keep it somewhat controlled, I will screw in the same bulkhead/brace/trans (maybe case) that I install on the aluminum chassis for testing, but obviously nothing for the front. In theory, I don't think these components do anything, and I could just clamp the chassis to the table at the location of the trans for the same results, but to try to keep it more fair, I will go the extra step. The plan is to literally place a clamp on top of the trans brace to hold it solid to the table, and apply upward force at the front.

Most of the chassis tested will be blank / empty except for the required components, but a couple will be built. Sorry, too lazy to take things apart to make everything equal. I don't think the accessories will have an impact. I have A B C aluminum tubs just for fun, but I would imagine any real differences in them would be because of use, and not because of original traits.

Oh, and I understand that I am conducting a pretty worthless test, and it means nothing in real world. I am not trying to prove anything here! Just pulling on chassis and recording numbers. Take that for what it is worth.

The contestants so far:

EDIT: added a ReRe and a ReRe stripped to the mix

[Frankentruck]

I noticed my TQ10 chassis is more flexible than my RC10 Graphite chassis. The FR01 would be interesting to compare.

[morrisey0]

I noticed my TQ10 chassis is more flexible than my RC10 Graphite chassis. The FR01 would be interesting to compare.

While just playing around with everything, I was just flexing all of them a bit, and found the TQ10 (with tight battery in it that is arguably a brace) to be noticeably flexier than the other graphites. But again, that is just impression. Need facts!

[Frankentruck]

The TQ10 is a thinner chassis too.

[morrisey0]

So, the first page of this post may just be me remembering/finding various chassis. I remembered I had a CC oval chassis (on a great project I need to get back into), so that adds an original CC to the mix. I honestly don't know what the straight carbon chassis in the original pic, if anyone wants to chime in.

I know I also have an original TrackMaster oval chassis in pretty bad shape, but if I can find it, it is going in the mix.

[JosephS]

It’ll be to fun to see. Especially if it compares built to unbuilt.

With the front nose tubes and a the rear motor mount and bulk head all connected I’d think a tub would be stiffest, unbuilt it would have the most flex.

[1911Colt]

It would be good fun to also test some of the chassis racers "lightened" (aka butchered).

[MarkyDents]

This is some good stuff, definitely interesting. In my mind I always thought that the whole big difference between the tub cars and the flat graphite cars in the way they would act in a racing environment would more so be their ability to twist flex.

[Dadio]

Cool idea , I do love putting lots of effort into testing things for worthless results
Only thing I might add to even out the results is to fit steering servos as they might well add stiffness.

[morrisey0]

I would love to test them all complete, as I think many accessories have an effect, but unfortunately, I think it will be years, if ever, that all these chassis get built. So I just gotta go with a base at this point. I will do a couple of complete cars at the end, as I am mainly interested in how the FR01 compares to a standard aluminum pan based RC10. How the FR01 compares may decide its fate in the long run.

I decided to scrap the dial indicator idea, because, well, what a pita. Instead, I am going with fixed heights, about 2mm apart. Basically, have an adjustable rod, and flex the chassis to that rod height and measure force just as it approaches this height, then adjust rod up 2mm, etc. Problem there is that the starting point is always different between the chassis, so I have made my rod adjuster mounts adjustable. I can then dial in the mount with a (maybe 1-2mm spacer) so that the starting rod height from the chassis is the same in every case. The staring point won't be the same height from the table, but the same height relative to the top of the chassis.

I built my adjusters to handle about 1" (25mm) of flex at the point where the front arms would be. Really don't think I want to bend the aluminum past that point if I even get there. They can always be built to handle more if it is deemed necessary.

Side note that I learned while putting this bulkhead / rear end in, that I never noticed when building before. Maybe it is just this chassis, or version of chassis, and I tried it with two different bulkheads, but with everything mounted except the bulkhead side screws, the chassis sits close to flat. But at this point, the side bulkhead screw holes are about half a hole off, and when you line them up and install screws, it puts more bend in the chassis. I will watch this more as I play with the others.

[morrisey0]

So I got into the testing this evening, and it started off great with the aluminum tubs, but then ran into a snag with the graphites. I am not a physics guy, so I don't know if what I am stating here is correct in the physical world we live in, but I am just reporting what data I have seen.

I started with all the aluminum tubs, mounted as shown above with the transmission brace clamped down, and I was happy with the results. No crazy outliers or anything, just believable data. As I was testing these, the entire rear portion of the chassis stayed tight to the board, and the flex or bend was seen in the chassis from forward of the bulkhead.

Then I installed the AE RC10 graphite chassis, using the same bulkhead / trans / brace set up, and clamped the same way. The initial heights required more force than the tubs, but then the force required seemed to stay the same as I raised the height, and I then noticed that I was "rocking" the clamp backwards and lifting the chassis in the back. Couple of grunts on the clamp ended up with about the same results. The graphite chassis was more rigid, and wanted to remain straight, and would rock/lift the clamp before bending any further. I then altered the testing apparatus and removed the trans combo, and simply clamped the rear of the chassis to the board, and repeated the test. With doing this, the rear of the chassis stayed solid to the board, and the only flex witnessed was in front of where the bulkhead would have been.

I am not sure how to continue testing with keeping the control variables relatively equal. And TBH, I really don't want to put too much more effort into this venture. I really just wanted to see how the flex of a FR01 compared to an aluminum tub RC10, which I haven't even done yet! From what I witnessed tonight, no matter how weird the data looks, I am convinced that an AE graphite chassis is more rigid across the board than it's aluminum counterparts.

The below is my oz to mm chart in raw form so far. The graphite numbers are with it hard mounted without the trans combo.

[Frankentruck]

The TQ10 flexes more than the Graphite. The G is a super still chassis.

[JosephS]

It makes sense to me the carbon fiber is more rigid than aluminum. That's it's thing. It will also have less elongation if you decided to stretch it. It's just once you get to a certain point of force it will fail catastrophically, where the aluminum tub will just bend.

[morrisey0]

Data. Use at your own risk. I ran the FR01 chassis test twice. Weird that as a bare chassis, the FR01 seemed much more rigid than anything else, but as a complete assembly, it kinda fell right inline with the others. The aluminum pans really do benefit by bracing created by accessories; servo and mounts as Dadio suggested, and I even think battery stays help. Hmm, maybe I will run another chassis test of an aluminum chassis just as above, and then add just a servo combo and battery stay.

Again, the whole purpose of the testing, for me, was to determine if the FR01 would flex more than a typical aluminum pan. The methodology here is loose, and no data should be considered truly accurate, but it provided a result for what I wanted to test. The next phase for the FR01 can commence.

[RogueIV]

Data. Use at your own risk. I ran the FR01 chassis test twice. Weird that as a bare chassis, the FR01 seemed much more rigid than anything else, but as a complete assembly, it kinda fell right inline with the others. The aluminum pans really do benefit by bracing created by accessories; servo and mounts as Dadio suggested, and I even think battery stays help. Hmm, maybe I will run another chassis test of an aluminum chassis just as above, and then add just a servo combo and battery stay.

Again, the whole purpose of the testing, for me, was to determine if the FR01 would flex more than a typical aluminum pan. The methodology here is loose, and no data should be considered truly accurate, but it provided a result for what I wanted to test. The next phase for the FR01 can commence.

The sides of the tub being bolted to the bulkheads essentially acts like a double-decker chassis would.

I find it interesting that everyone likes to claim the RERE chassis is ultra flexible compared to the old chassis but here it is being incredibly close to the numbers from the OG A stamp.