A Question for you Scalextric Experts...I Give Up!

[strummer57]

Here's something I haven't seen before. This recently acquired BRM runs really well; as long as the upper half of the shell is not attached.

I run it off a 9volt battery, and everything is fine; but if I try to lay the upper half in place, the motor will begin to bog down, and if I continue with the process, the motor will stall and quit running completely. It doesn't matter if I start at the front of the car, or the back: the results are the same.

Obviously something on that upper half is pressing down on the motor, but for the life of me I can't seem to find out what it is. Since this is only my second vintage Scalextric car (and my first BRM), I don't know what a "healthy" example should look like.

Am attaching a couple of photos; maybe you will see something I don't...



As always, thanks in advance.

Mark in Oregon

[chrisguyw]

Mark, check to see if the lead wires (both at the motor brushes and the guide pin) are not frayed, and have good solder connections,...and secondly, sometimes the top half of the body can come in contact with the grommet holding the lead wire/motor brush, lifting it off of the comm.

Cheers
Chris Walker

[strummer57]

Thanks Chris. I know the wires are OK, so I will look into the other thing. I'm wondering if the posts that hold the windscreen in place could be the cause; I see they are pretty long...

EDIT: Nope, not it. I trimmed them back flush with no results. I'm wondering if the entire lower half is slightly warped, so when the upper half is attached, both halves are trying to aline themselves with each other, and causing the binding...(?)

Mark in Oregon

[chris]

In an earlier post you said when the BRM arrived it was missing the front pin to clamp the body to the chassis. If that is still missing maybe the body tilts back on acceleration and causes a bind? Its a great looking model, I have the re-release Power and Glory version.

Cheers,
Chris (in sunny Canberra)

[strummer57]

Hey Chris

A good guess, but I don't think that's it. This odd binding shows whether I latch down the back or not; and, as I mentioned earlier, it does same thing if I latch the front first. It seems to be happening when the center part of the upper body gets "snuggled" down to the lower half. I've tried re-routing the wires, adjusting the pick-up assembly, everything I can think of. I will say this does not happen if I remove the rear axle/gear, so maybe I'll look there next.

Since this is the first Scalextric BRM I've ever seen, it's hard to know what to look for; it's a puzzler, that's for sure!

Mark in Oregon

[strummer57]

I just spent another couple of hours trying to figure this out, but with zero success. The only difference I can see between this and the Lotus 16 I got a while back is that the (2) alinement pins on the sides of the Lotus are gone, and the ones on this BRM are still intact. Is it possible that these "pins" are causing the shell to somehow contract and "pinch" the mechanism? I know it's a stretch, but I've tried everything I can think of. I have attached a couple more photos of each vehicle.


So farI have:

Re-soldered all the connections;

Slightly trimmed the molding of the upper shell where it's supposed to contact the motor;

Trimmed the mounting pieces for the windscreen, as they were sticking down quite a ways;

Ever so slightly enlarged the molding clips on the lower half that holds the rear axle, as it seemed REALLY tight; (on the Lotus this connection is nowhere near as tight, and it doesn't have this binding issue)

Ran a file along the inside of the rear axle between the gear and the brass "cone-shaped" spacer, just to make sure there was enough play between it and the gear shaft on the motor;

Probably a few other things I don't recall right off.

Once again, it anyone has any sort of suggestions, I'm all ears, as this has me completely stymied!

Mark in Oregon

[Dodgefarmer]

Does the rear axle spin free by hand, with and w/o the top attached?

HTH
Randy

[strummer57]

Does the rear axle spin free by hand, with and w/o the top attached?

HTH
Randy

Good question, Randy

I just got home, saw your post, pulled the motor, and yes, the rear axle spins freely, whether the upper body half is attached or not; so I guess we can eliminate that possibility...

Please keep the suggestions coming!

Mark in Oregon

[Mike SoCal]

Could the upper body half be altering the tension on the two brushes?Binding or removing the tension.


mike

[strummer57]

Hello again.

2 (more) hours later, and this is what (I think) I found.

As you can see in this first photo, both top and bottom halves line up (more or less) correctly:



In this second picture, note the gap between halves:



It was much worse; what you see here is after I spent a fair amount of time carefully sanding the bottom half, between the front of the back axle, and where that vertical line is, just in front of the cockpit.

The motor will now run with the top attached, so I think the issue was indeed the lower half was "out of whack"/warped on that side for whatever reason...

I have tires on the way from Paul Gage, so I am looking forward to seeing it actually run!

Thoughts/comments/suggestions?

Mark in Oregon

[chappyman66]

Hi Mark,
A little body warp can happen, especially with clamshell cars. I have the new Gurney Eagle, and had something similar when I took the magnet out....I had to fiddle with it for awhile to get everything running freely again.
That much warp can definitely cause binding. I haven't worked with those cars, but sometimes a bit of boiling water and a twist will straighten things out.

[strummer57]

Hi Mark,
A little body warp can happen, especially with clamshell cars. I have the new Gurney Eagle, and had something similar when I took the magnet out....I had to fiddle with it for awhile to get everything running freely again.
That much warp can definitely cause binding. I haven't worked with those cars, but sometimes a bit of boiling water and a twist will straighten things out.

Thanks Chappy.

What did you have to do to get your Eagle healthy? It might be something worth sharing...

On this thing, the "warp" was on one side only, so I'd guess the "hot water" treatment probably wouldn't have worked; in any case, I'm happy I was able to get it to where it is now, as the motor runs really strong.

Mark (still) in Oregon