Tuesday, June 28, 2011

Jigging the Caledonia chassis

Chassis on jigI'd hoped that the chassis construction for Caledonia would be quick and simple. It's got 6 wheels and I wasn't planning on any of that fiddly compensation stuff, so how hard could it be ? Better still, if I stuck the thing on the Hobby Holidays jig, assembly ought to be a matter of a few minutes work ?


First up I laminated the rods. These are very thing in places as per the prototype. No complaints there although I suppose the tags holding them to the etch could have been a bit thinner.

Then I used these to set the axle positions on the jig. The holes were too small for the ends of the jig axles but I reckoned I'd got them set properly anyhow. Despite this I had to move one axle bearing over 1mm inboard by filing the ole out a bit. At least the jig kept things flat I hoped.

Then with the wheels fitted, I tried the rods. They bound. OK, so try one pair of wheels at a time. After lots of hole opening I managed to get these to rotate. Then the third axle. More hole opening. At the ends of the rods, the holes are oval slots rather than round.

The chassis now runs when pushed along the bench but I have a nasty feeling that a new set of rods will be required to get it moving under power. What I can't work out is where the problems come from. Did I set the jig up wrong ? Is there a problem with the kit ? Was I just having a bad day ?


Alan.Halse@btinternet.com said...

Hi Phil,

In addition to your three suggestions, I would add that it could be the wheels. If the throws aren't exactly the same the rods will bind.

However given that you said you had to adjust one axle bearing, I would put my money on it being the set up of the jig that was wrong. I would suggest checking the chassis using a flexi chassis jig ie long axles with pointed or stepped ends over which you fit the rods. If they don't fit it's the chassis. If they do, check the wheels...

Alan Halse

Phil Parker said...

The wheels are Romfords so I don't expect there will be any crank throw discrepancy, or at least if there is one it will be beyond my ability to measure it.

My suspicion is that there is a combination of dodgy jig setup and possibly an error on the etch. I'll go with the jig though as at least all the axles are square and flat. I can make new rods to fit if required.