How to straighten Monogram brass chassis (warning, lot of pictures)

[oz10k]

I won an auction for a Monogram Ferrari with a customized way to mount the can-end motor:



I've removed the odd parts and want to mount an end-bell motor, which I believe is what the car originally came with. But the rear part of the chassis is not straight, and I'm pondering the best options to fix it. Here's a bunch of pictures showing the issues:


















The best I've come up with is to slowly spread it apart and hope it returns to being square. I was thinking putting a long screw in the bushings, then slowly rotating the nuts to expand it, kind of like this:




Your thoughts?

Thanks,
Ron

[4424ever]

I think your on the right track but if it were myself I would clamp the cross bar at the back with the body mount solid in a vise so each side could be spread out separately
This way you could bring out each side to square with out buckling the mount or inducing a diamond into the frame

[noddaz]

Yeah, what Dave said. Also maybe screw the body mount to a block of wood that fits the the width of the chassis if you don't have a vise. And then slowly and gently tap with a punch and small hammer to bring the back of the chassis straight on both sides of the body mount. Then slowly work you way up each rail, alternating sides. You might want to find a piece of steel that that fits in the unbent part of the chassis rail (Like your ruler but fits snugly) and use it to slowly straighten each rail out. If you have a square you can use that as you go along to see how the chassis is coming along. You might find yourself doing all sorts of crazy stuff to that chassis while fixing it. Like clamping the right side rail down to something and gently using pliers to bring the upright back to vertical near the right axle bushing. That chassis has been well played with!

Take your time and good luck!

Scott

[oz10k]

Thanks Dave, Scott. I did spend probably an hour on it. It's not perfect, but an axle now spins freely, so I'm pretty happy with the results. Ron

[chrisguyw]

Hi Ron, It is unlikely that you will get the chassis back to perfectly square and flat (not that the Monogram chassis ever were !!)........but, you can overcome any minor tweaks when soldering in the bushings.

Here is a procedure if it helps.....

1/ Use a round/half round file to slightly enlarge the holes in the axle uprights so that the bushings (all 4) have just a small amount of movement in the holes.

2/ Install the bushings and axles, and use some gears/wheels etc. so that the chassis sits off of your set-up plate/jig. The front and rear gears/wheels, do not need to be the same size front to back, but, they must be the same diameter left to right.

3/ Make sure that all 4 gears/wheels are touching the jig/set0up plate and solder the bushings in place..........this will ensure that both axles are on the same horizontal plane, and this will overcome any minor bends/tweaks in the chassis.


If you do have a jig, it can be used to also ensure that the axles are also parallel.........if you do not have a jig, you can make one, or use a piece of graph paper (taped to your set-up block) to help ensure that the axles are parallel.


Cheers
Chris Walker

I do not have a handy pic. of any of my vintage chassis on a block, but the attached pic of a plastic chassis, should illustrate the alignment using a jig.

Blocks, gears, wheels are used to ensure that the chassis sits "off" the jig surface, with all 4 blocks touching the surface............the jig also allows me to align the axles so that they are parallel.

[oz10k]

Chris, thank you very much for the excellent idea and clear instructions! I do have a jig that I bought from Chris Briggs years ago, I'll give your idea a try. Ron

[chrisguyw]

Ron , Mr. Briggs' jig will be just fine ,........you may want to consider adding a few braces to the Monogram chassis as they were notoriously flimsy,.....it will prevent future bends, and will considerably aid performance/handling.

The major areas of concern are the guide tongue, front and rear uprights, as well as the overall longitudinal flex of the chassis.

Here are a few shots to give you some ideas.........

Cheers
Chris Walker

This is a 1/32 Monogram chassis, which had the same "flimsy" attributes.



Some .047 piano wire running the length of the chassis




A brace for the really flimsy motor mount.



A front end brace, and piano wire "L's" to support the front axle uprights, and , they are trimmed to act as guide rotation stops.




The finished roller.......



A .063 brass pan was cut/mounted to the chassis bottom with brass screws....it has silicone washers between the top of the pan and the chassis plate bottom, to reduce vibrations/noise.




And an AMT chassis with a front axle tube, added , rear piano wire axle brace, and a few other not so obvious braces..

[oz10k]

Thanks for the suggestions Chris.

Wow, the quality of the work you do is absolutely outstanding! I know mine won't look as good, but I think I can get most of the functional improvements.

I do have that AMT chassis sitting in a parts bin. You've given me some incentive to take another look at it.

Thanks again for all of your support!
Ron

[chrisguyw]

Ron, build that AMT !!,..it was arguably the best production brass chassis of the time,........it will run rings around the Monogram

[Model Murdering]

Kinda late, sorry!

Dents and bends should always be approached using the "worst is first" method. A small square is the ticket for eyeballing as you work. A set of dividers allows you to cross measure easily, so you can tweak your corrections.

In this case, I'd start by standing the good part of that 90 degree tail kick bracket in a non marring vise, and focus on straightening the two 90's; as well as the vertical drop between them. The vertical drop from the top 90, the bottom 90 and the small 90 degree single ply transitions; are where the bulk of the stress is stored.

For the interim, release the screw/gusset, so that the frame rails can flex out from their pinched position. This will exclude the added stress of trying to force them into submission, while executing the primary correction bends. Due care and caution should be exercised at the single ply transition points between the tail and the longitudinal fame rails. Brass fatigues easily, bent brass, more so. For this reason it's best to putter along, and never try to take too big a bite.

I never strike with anything harder than the frame material. Pine or nylon bits are used to deaden the blow and help prevent marring and stretching. Alloy jaws for ones vice is good. I have a favorite set of old pliers that were near toothless. I didnt take much to smooth them. Leather pads or common masking tape in a pinch, allows for gentle manipulations.

As the gnarly bends come right, the little stuff often experiences preload towards re-direction, and becomes waaaay more cooperative to your efforts.