Thanks for the heads up Nigel. I've added fillets to all the fold lines and joints, but that unsupported forward motor mount is suspect. Maybe I'll tack on a structural support for insurance.
The aft motor mount is fixed on three sides so it should be sturdier than the forward mount. If the forward mount snaps off, I suppose I'll drill holes in the aft mount and use screws to fix the motor.
Post by Andrew Rowland on Mar 2, 2020 1:48:54 GMT -5
Once it's all bent into position run some solder filets up the joints and vertically where surfaces touch. Haven't built one for nearly a decade but that was the solution I found and they still run well. Andi
Post by David Mitcham on Mar 2, 2020 3:26:09 GMT -5
Looking good. To emphasise what Andi writes if you make sure all the joints are well soldered you will have no problems. I recently had two cars in a proxy with PP chassis (mandated undertake rules) and they ran without breakages as did the other 15 or so cars with similar set ups. I think I would consider putting screws in the rear motor mount as insurance and to make sure the motor doesn't move - either that or solder the motor to the bracket.
Thanks for the tips. I've already soldered all the joints and folds but as noted, that forward motor tab is still suspect, even after running a fillet along the fold. The tab is very rigid but that is what makes me suspicious; it is completely rigid with no flexibility. I'd guess that it might hold up well enough to snap the motor into place one single time, but I wouldn't want to remove and re-install the motor more than once. Oh well, if it breaks, it breaks
Post by Peter Seager-Thomas on Mar 4, 2020 17:40:33 GMT -5
I cannot get my head around a metal chassis which must be 'sprung' to fit parts, either motors or axle bushes. Plastic springs if it is soft enough, metal in such situations, does not. The (PP) chassis would have been far better if made with a screw mounted motor. The idea of any rear axle bush (other than one which is soldered) in the 'push in' axle mounts is laughable.
I think the concept of these chassis is brilliant. The detail design work is awful.
I do have two tucked away in case I should need them. They WILL be modified.
Sticky tape...lol. It may come down to that. It is a good starting point for a chassis, in that one doesn't need to design and cut out all your own chassis elements. Lots of people have been using this chassis for many years with great success, so it must be okay. So it's up to me to make it work.
This chassis came with a kit. I didn't know if I would ever use it, but imagined that it might be useful for a quick simple build. Fold it up, slap a body on it, and away you go! But of course, it is never that simple. I've now spent a few hours on the thing, and it still needs more work.
I'd agree Peter; a nice concept in which a few of the details could be improved.
Maybe the forward motor tab could be a separate piece, in the same way as the front axle/guide assembly is a separate piece. Then the motor tab could be movable and slide into position to capture the motor boss.
And holes for motor screws or marking the drilling locations would be helpful. Of course, I could have anticipated this and drilled holes for motor screws if I had been paying closer attention. If I ever use this chassis again, I'll drill the holes before bending the tab up into position. Drilling into the now vertical tab at an oblique angle is going to be a sloppy operation.
The guide holder needs some work. The hole for the guide post is quite a bit larger than any guide I have, so the guide is flopping around in the holder. It will need to be sleeved with a brass tube, and of course I don't have the correct size. I suppose I could solder on some washers or a chunk of brass and drill it out to the correct diameter.
I have a few of these chassis and I think they are great, the guide holder is the only thing that I think needs improvement, although improvements in other areas wouldn't harm. The only proxy race I won was with this chassis and it beat Taffy, what more can I say, very proud of that feat. The motor was only held with the tabs also, the latest one I am using has the aforementioned engineering modification of some electrical thermistor heat resistant tape to assist in securing the motor more securely. Regards Nigel
Sorry folks, forgot to wrap this thread up. This car did eventually get finished. The PP chassis works well. I can see using more of these chassis kits, they are useful items. I've done thousands of laps and it is slowly getting better. It was a bit stiff at the beginning but it is now starting to loosen up and run more smoothly.