47 replies to this topic

[Isaac S.]

That's very cool. Is the Riggen guide flag you described earlier just a copy of the Dynamic? Cobra spur? Not to be nit-picking but it doesn't seem your motor has the brass post protectors, these should be on that motor. Again, just trying to be helpful. 

 

Great job, it looks fantastic. 

[ajd350]

The Riggen sure looks like a Dynamic. Maybe they acquired the mold. I don't know what the history of that Mura is. It is just the way it came to me. I have some of those protectors. I'll probably put them on. Yes, Cobra gear.  Thanks

[Bill from NH]

I ran both Cox & Cobra gears on weekly race cars back in the 70s. The Cobra spurs were thicker/wider & I thought ran truer than Cox. I've heard recent complaints about the Cobra, but I have no idea what was used for pinions or if maybe there was just a bad batch of gears out there. I never experienced any problems running them. In the 70s, here was  also a clone of the Cobra spurs by a company called G&W. 

[tonyp]

Cobra spurs were noisier because the material I believe was harder. We ran them with the cobra pinions


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[Pablo]

Not to be nit-picking but it doesn't seem your motor has the brass post protectors, these should be on that motor. 

 

I'd like to nominate Bill as Official Historian of Slotblog, and Isaac as Slotblog's "Vintage Police"   

[Bill from NH]

When it's stuff I never had, I probably wouldn't know about it.  I haven't kept up to date on much of anything in the past eleven years.

[ajd350]

On closer inspection, the post protectors are in place, just with enough patina to be hard to notice. I don't think the motor has ever been opened.

[Bill from NH]

If the motor still has pintabs, you're probably correct Al. It's not been opened previously.

[Isaac S.]

Very good, thanks.

[ajd350]

If the motor still has pintabs, you're probably correct Al. It's not been opened previously.

You mean I'm the only one who puts them back in?...LOL

 

Yes they are, and not scratched up.

[Bill from NH]

Yes, you're the only one I know!    The first thing I use to do to Mura motors is pull the darned things out & replace them with screws. In my slot box today is a pair of fingernail clippers with mangled cutters that I used to pull them out. 

[Pablo]

What Bill said, exactly. I have a special name for those pin tabs, but I can't say it on a family forum LOL

[Bill from NH]

Let's just say they weren't very "user friendly."   I used to throw mine away so nobody else could reuse them.

[ajd350]

I had a chance to run the car on my friend's hillclimb last week. Fun car to run and plenty fast . I ran modern tires with light glue (it's what he had on hand) and it would chatter coming hard off the turns which I heard is characteristic for these chassis types. We cleaned the glue from the tires and it was much better until the tires picked up the glue again. It was fun just to see what it drove like.

[Pablo]

Brace the motor to the axle tube opposite the gear end and the "chatter" (I call it "bunny hop") will end. Here is an example, although in the photo mine is just tacked in temporarily and mine's a can drive. But the idea is the same - secure the motor opposite the gears so the motor cannot wiggle up and down

 

 

 

If you want evidence what I'm saying is true, grab the car with one hand, the shaft opposite the gear end, and try to wiggle the motor up and down with your fingers. If it's not braced (which I think it's not based on your photos), you will be able to feel what I'm talking about. Anglewinders always need that bracing. How you do it isn't as important as just doing it. I recommend Aero paste flux so you won't splatter acid over your rear end 

[Rotorranch]

I always preferred a low mount brace. It just seemed easier to change a motor.

 

Rotor

[Pablo]

I hear ya Jeff. The low mount has the advantage of lower weight, albeit minimal. It all depends on the chassis design and what type motor. On 70's chassis when motor boxes were obsoleted by one straight rail under the EB side and one bent rail on the gear side, can drive soldered to left rail, I prefer the brace up top because it's not only opposite side, it's opposite end. Makes it even less prone to wiggle, is my theory.

 

Modern FK motors get by just fine with the extra brace down low. But they don't have near the amount of torque, weight, and heft of a 70's Mura 16D. 

[ajd350]

I looked back at the last pic I posted and the angle of the shot makes it difficult to see the brace from the axle tube to can. There had been one before and I placed it back on similarly to yours. Thanks for validating what I thought should be there. I think a different tire compound and maybe some strategically placed weights would get the rest under control.

[Pablo]

I still say it shouldn't be chattering. I have more ideas:

 

-try a new axle

-worn bushings/BB's

-worn motor bushings/BB's

-axle bushings have come loose from the axle tube

 

Doctor Pablo

[Isaac S.]

I would agree with Pablo, before trying weights make the motor box as sturdy as possible. Solder axle bearings in the tubes if not already, replace worn bushings, or the axle is worn or even slightly bent. Chatter, especially in anglewinders is due to flexibility. So increased bracing in the motorbox area will most likely fix the problem. 

[Mike Patterson]

Nice job on the body Al. Did you paint it yourself? I think that body is a BRM.

The body is a Lancer Cooper repop.

 

You also might try narrowing your rear tires to help with the chatter.

[ajd350]

Thanks for all the suggestions. The axle is true on a flat glass plate, runs in new close fitting bushings that press fit in the tube. I see that an L brace on the lower front left side of the can should take out the rest of the motor box flex. Be that as is may I will leave it was when is was built originally. I don't race these cars, just putz around and admire the old builds. It can always be added later.

[Pablo]

new close fitting bushings that press fit in the tube. 

 

Bingo, there is your chatter problem. The bushings need to be permanently secured with solder to the tube.