27 replies to this topic

[Rick]

I have been of the opinion that a motor bracket should be stout to start out with. This is why I have always made mine from .050 thick material and to use direct fit oilites or bearings, with no need for 7/32 tube. The bend area, IMO, is very important for the integrity of the unit and the more mass here the better. Of course this makes for a heavier unit. With the rend to add things in the rear of the chassis, such as a backatcha etc, I really didn't see the logic to make the brackets lighter and lighter. BUT, BUT, racers/builders like to lay their car on a scale and come up with as light as possible to the 100 gram minimum.

I then progressed to a couple of scallops to remove some high weight but still leave enough material in the bend area to be robust and still not rquire any extra bracing. Weight now about 8 grams.

Still many carve up the my brackets and want to save more weight? MInd you I have to work inside the paramters set down by my bending die, so I have to be aware of that. Some don't like the blunt edges etc.

Ok a new generation of my bracket must be born. Today I looked as some blanks and started a R&D project to remove a little more weight and still keep the integrity of the piece and not require any extra bracing. It must also still work with the backatcha piece and still use my punch and die set.

SO here is the latest evolution of the R-Geo bracket*. This is probably not the final version but closer to what some of the carvers are doing now. It's down to 6.2 grams true weight.



Now my discussion part:

Do you prefer a light bracket like the Dubro, for example, and lots of bracing or one that is thicker material and does not require bracing to provide integrity?

How rigid does the motor bracket have to be? IYO

Have yo ever weighed the bare bracket and then weighed it again after the bracing is installed to see exactly how much weight the bracing has added? How much?

DO you prefer the 7/32" tube to hold your oilites/bearings more than a direct fit and why?

* This is not for sale yet and when they are avilable, I will post in Parts Counter with the final version. Lastly, the oilite holes will now be done differently to be much more accurately located and will be avialable hypoid and straight...........

[slotcarone]

Good questions Rick!!! My own feeling is that no matter how thick the bracket is if you hit it just right it is going to bend unless there is some kind of bracing. I also prefer to use axle tubes with a minimum of spacers since this will hold a gear mesh better IMO. The axle tubes also give you an area to solder the chassis rails/bracing to.

[Mopar Rob]

For 1" I prefer .040" with 3/16" holes for bearings. I think the 040" is a good compromise for strength vs weight. With the 3/16" hole one can install bearing directly into the bracket and if one prefers or the build requires an axle tube one can always ream out the hole to accomindate as long as there's enough material around the axle hole.

[Mark Wampler]

All my brackets start out .032. As was mentioned, brackets will bend without bracing and for me in planned key areas. .032 is easier to configure. Because its light, I have more options to add weight where I want for lower center of gravity/ traction purposes. I line the inner/ upper portion with .055 rod and of course the bottom is surrounded by a minimum of .062 main rail. Depending on how wide I choose to make the bracket, double wall axle tubes provide plenty of stout against wall shots .

[Cap Henry]

I like using axle tubes. I don't like using the rear collars do to my 1:1 racing beliefs on always trying to reduce rotating weight. But it's prolly a mute point, as Hershman runs them with MUCH success.

Another thing with the axle tube is that it leaves less axle hanging out to deflect or bend during regular racing conditions. Again, just another thing from my 1:1 racing. But if you look at alot of the newer flexi cars, the rear uprights have gotten wider...

[Hipsticker]

its early morning and since any opinion is veiwed here ill chime in ...As CAP said in his post ,real race cars tend to keep the rotating weight to a mimimum,i cant ever go against that overall reality.No matter how big or small ,rotaing weight has to be slowed down and sped up,that takes energy.It aslo has to be rotated left and right for corners,that makes the pendilum effect grow at a huge rate,Rotating ,swiinging weight in the rear of any race car unbalances it probly a lot more than we think it does.[look at real oval track cars how much they fool with placing and shape of the fuel cell]Seems in looking at the "fast" cars ,the 3/4 wide box with longer tubes is popular with builders.But also on other hand as CAP stated Hershman uses collars and kicks rear any day,so mayby were all thinking too hard ,...lol Myself i just want the motor to BOLT in properly,square with axle,im way against heat and solder on any motor,just a peeve i have. I have sat here and llooked at all my cars from different builders,thought a bit ,have a bunch of different configurations to look at ...One thing that pops in my head is the "sound" different cars make ,ive noticed that ..i dunno why or any technical stuff ,but the small 3/4" box cars always sound more precise and "perfect?" for lack of words than wider box cars ,,mayby all the moving pieces are spead out further reason? i dunno just adding data to ponder ...thanks hip
i bet if Duffy chimes in we will have thoughts to wonder.

[Old pink can guy]

After a 18 year layoff I have only built two kits A JK and A Warmack. I also have some BPR rear brackets. So far I will take Bryan's over all the rest. It is stout and square no muss no fuss. Rick your's looks great. When I get a job I would like to try one and order some more goodness from you. The Jig and wire bender O do I wish I had them 40 years ago! Ken. They work great thank you.

[Duffy]

i bet if Duffy chimes in we will have thoughts to wonder.

That's nothing, I wonder at my own thoughts three times before breakfast!
Actually, where I don't have the race cred to command listening, I see a couple things worth thinking about here.

The joke used to go--maybe still does--that if Cukras won with a yellow car on Sunday, by Tuesday practice everybody'd be running yellow cars. What works for one guy's fine, but just maybe it won't work for another. The best setup for anyone oughta be one he understands fully, so he can see what's going on in there and also one he responds to well--think of it as a combination of systems & structures that mete out qualities of both aggressiveness and forgiveness suiting just one individual driver.

Dunno what was getting used for axles before I wandered in here; but I've seen cutoffs from ejector pins and thru-hardened core pins packaged as axles by some suppliers, and both are stiffer than "music" wire but still bendable. When we went more toward reamer blanks for axles, we got a lot stiffer.
The different requirements of the two make different demands on bracket and extenders: a bendable axle needs support close to the area of probable impact, and unsupported axle length just becomes more leverage for a bend. The rigidity of drill blanks is way higher than the other stuff, and since they maintain their straightness over a greater length, you actually take advantage of their springiness to move your bearings inboard and let the axle flex in a high load, spreading the impact out in time and distance: a bearing right out by the wheel would be just a hard stress riser, a snapping point.

Something to remember when making choices about structures: adding things on to add rigidity or to redistribute mass is also increasing points of possible deformation and breakage--you're adding ways the structure might fail, and adding places you might not notice a failure when it happens. That doesn't mean built-up is wrong, it just means you gotta think what might fail as you build. A gross example is, bracing on the outside of a crushable bracket invites solder joints to pull away and tear, while a wire on the inside will just compress. And so on.

I'm currently somewhere in the middle with this stuff, making mucking great .062" brackets and laying 'em into the frame--and then cutting back down again with my Dremel until I figure it's about right. It's not a logical way, it just makes me feel more secure during the build; and I can then judge what I think I've got at the end of things and whittle or brace with the whole chassis to look at. Just my way.

Duffy

[Old pink can guy]

Duffy thanks I never ran the same color bodies That John or Mike And Terry Ran. But I did make my Mom drive me to Speed and Sport to pick up the latest copy of MRJ. That was my go to for builds. Great post by you. Many things to ponder over. Thanks Ken.

[Mark Wampler]

Something different, rough experiment.

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[Duffy]

How'll you get a gear in that thing? See, you didn't think this through.

[Duffy]

Okay, that was fun. But--actually, Mark, this shows great potential for guys not fixated on every gram above the bedding plane. Using the bent cheeks for shear strength along the extenders like that, you can go to much thinner material in the bracket; and you're not depending on wire-to-brass joints back there. & once everything's in place, you can pare away up above and make it look more reassuring again. Interesting.

[YetiSRP]

Rick, my man,

I'm going to be using the thinner REH-purchased brackets on my new in-lines for a very good reason; I have a lot of them left!

However, the 'fault' in them turns out to be an asset. Because I'm using my standard guide plates (they're not really drop arms, are they?) I place a piece of .063", same width as the guide plate, under the notch. While I'm still adding a brace up top, this layout has the advantage of keeping the extra weight of the .063" material down low.

While there are pros and cons for the tubing layout, I could either use tubes (pural---2 thickness to reduce down to for the bearing) or leave the hole for 1/8" axle and use the step-down bearing for 3/32". Got a lot of them, too. The advantage I see to that is the you buy a chassis from someone set-up with the tubes, put some of your special tires on it, measure, and it's like; 'Oh...poop'. Or words to that effect.

Which is why I'm including a pair of those reducer bearings with each chassis now.

The other advantage, because the hole is that large, you can add your own tube(s) and change the track clearance, if you're of the mind.

Just sayin'.

[Hworth08]

Eventually wide brackets will win out (pun intended). Just like anglewinders's main rails kept getting wider so will inlines.

Slot cars handle better with most of the weight on the edges of the frame. Someone will win a big race with the rails spread an inch and a half or so wide, then the rails will get as wide as the tires allow.

[Bill from NH]

Jim, those 2-thickness reduced-down holes will fit both 3/16" dia. Slick 7 3/32" & 1/8" bronze bushings. Only if someone wants to use 1/8" axle bearings or 1/4" O.D. bushings will they need to use the REHCO bracket holes or ream them out to fit 9/32" tubing.

[Mike Patterson]

Rick,

I have always liked your motor brackets and their ability to remain true. I have had hits hard enough to pop the balls (can I say that?) out of a bearing, but the bracket has remained unharmed. I use a 1/16" U brace, and that's it.

I prefer axle tubes simply because they get the bearings out closer to the wheels, and reduce the effects of wear on the alignment. At least, that's MY theory.

To start some thread drift, is your new avatar by Frank Frazetta? Looks like it from here.

[Phil Smith]

Here's my thoughts--for what they're worth--on motor brackets:

If you just look at building a structure to connect the motor to the axle bearings--which regardless of how it's done, that's what the rear of every chassis does--a narrow motor bracket with axle tubes is a very inefficient and indirect way of doing it. Ideally you would go from the motor mount to the bearings in a straight line, which would require a motor. bracket with side plates that angled out directly to the bearings, eliminating the axle tubes. Well building a chassis with an angled motor bracket is a pain in the butt. An easier way to eliminate axle tubes is to build a wide motor bracket, which I see a lot of guys do.

So my thinking is, whatever width you want your axle bearings to be, build your motor bracket that width so you don't have to use axle tubes,

[Mark Wampler]

I’ve done both with fairly good results. If you build a super wide bracket, then plan on your main rail to also be wide. Light chassis with narrow pans work good. If you need wider pans, then the main rail(s) will also have to be narrow practically speaking. You can stab narrow rails into a wide bracket, but its not my 1^st choice. For a narrow bracket with conventional mainrails, extended, double wall tubes work very well.

[One_Track_Mind]

I'm going to be using the thinner REH-purchased brackets on my new in-lines for a very good reason; I have a lot of them left!

Bigger problem I see there using these Jim, is that there is no motor mounting holes to fit the smaller motors.When they are drilled out there so close to the original holes,not much meat is left there to hold them securely.

PLUS! there not a hypoid style bracket!
Got's to get the motor LOW as you can go!

[Duffy]

...a narrow motor bracket with axle tubes is a very inefficient and indirect way of doing it. Ideally you would go from the motor mount to the bearings in a straight line, which would require a motor. bracket with side plates that angled out directly to the bearings, eliminating the axle tubes.

It gets me wondering if we've thought ourselves into a corner, with these inline chassis.

It looks to me like this: way back at the beginning of things, we sorta willy-nilly divided the floppy pan width by the motor space and just used that proportion from then on. Right? Now, we've made that convenient: we run more-or-less straight to our nosepiece from that narrow space, and then we gotta jump through all kinda hoops to spread out from guide to front wheels--but we're used to that, so we just take it on as a necessary part of the process, like flossing, or Michael Moore.

But is that the only way?

Just for a moment, set aside that outboard area we normally fill with pans or whatever--that'll only muddy the problem--and consider: what're the challenges we might face by making a PROPER WIDE bracket/rail chassis?

Here're the points that jump out at me:

First, if we go to a ~1.6"-or-whatever-wide bracket, we've given ourselves an unsupported flat span across the bracket's motor-face or web plane. there's a max. .550" per side of thin brass sheet from the attachment screws to the bend to the bracket cheeks, and unsupported flat sheet bends & flexes & vibrates mos'unharmoniously, and we'll need to rigid-ize that quick.

Okay: rails off the cheeks, like we use now, that'll get some of the flex cleared up. Some. --But inboard of those cheeks, the mass of the motor can still swing like a bell clapper on that wide flat span, making flex in the place some argue we need the most stability: the motor-wheel unit.

So, okay, now let's fix THAT: brace the face. Cantilever-brace from face to cheek (still easier than a four-bend angled bracket!) and toss in a nice wide rearguard plate o the bottom for good measure.

All righty then. Added mass, added failure points, all for good reason. Informed choice.

BUT now let's look forward, and--where do our rails go? Splay out to axle mounts, a sort of Ample Tripod? Or inboard to the narrower guide tab? --Anybody? Anybody?

--And THEN we can talk pans!

I like this kind of problem.
I like when my own design paradigms get shook and I must mull over what-might-be about some attractive alternative or other.
What I'm doing here is trying to raise some Mullable Moments--I'm sure some of this has been tried and some has probably been dismissed or elevated to paradigm status, and I fully accept that this is completely Geeky Dumb Fun and in no way do I demand it be mandatory study to everybody this side of a Persistent Vegetative State, Texas for example, but--

Might be fun to puzzle out, to try out.

Duffy

[James Wendel]

Isn't there a law against using the word "paradigm" twice in the same paragraph?

[Duffy]

After tonight, going forward: yes. There will be.

[Mopar Rob]

What I'm doing here is trying to raise some Mullable Moments--I'm sure some of this has been tried and some has probably been dismissed or elevated to paradigm status, and I fully accept that this is completely Geeky Dumb Fun and in no way do I demand it be mandatory study to everybody this side of a Persistent Vegetative State, Texas for example, but--

Might be fun to puzzle out, to try out.

At first I thought 15 year old Duffy might have went to the Urban Dictionary but it was empty? I thought it might be a typo and should really be malleable, but then I was trying to figure out if it was pun intended or not? I guess as long as you're not refering to it as hooptie were safe?

[Duffy]

--Cool! Closer to mutable, maybe, but in a considerably more mentacious way. Why be limited to mere semantanalogopedagogics, anyhow? Go to sleep willya, it's a school night!

[Mopar Rob]

Go to sleep willya, it's a school night!

Not bad advice. I'm too tired to come back with anything other to say that you're obviously adept in the English language and not prosaic.