FITTING 2 CHASSIS LEGS

[fussyoldfart]

Fitting Chassis Legs: Xref - http://www.mmoc.org.uk/viewtopic.php?f=4&t=37282 and http://www.mmoc.org.uk/viewtopic.php?f=28&t=37359

I have one more question that needs an answer before we begin welding. We can't seem to get everything to fit.

If we put the eyebolts at precisely the correct distance apart according to specifications, and put the gearbox support in place with a couple of bolts loosely fitted to the new chassis legs, the front crossmember, the very frontmost one, does not want to fit. It seems to be about a quarter inch too long for the remaining space.

The front crossmember establishes the spacing for the motor mounts so if we narrow this space it will be very difficult to put the engine back in. If we separate the chassis legs to 15 ¼"" (400mm) between the bolt holes for this crossmember to bolt in, either the eyebolts are forced to a wider distance or the gearbox support will no longer fit between the legs.

How have others dealt with this problem please?

We, Chris and I, would really like a quick response to this one please.

Darrell McDonald

[bmcecosse]

I suspect 1/4" is neither here nor there in Minor chassis construction..... Fit the front member as is - and the wide stance eyebolts will help to eliminate any positive camber!

[taupe]

Hi

If its any help... from the front end jig drawing the front engine mounting bracket holes (inner) should be 15.186" apart (hole centres) and the outer holes a further 3.375" out from them on each side.

At the eyebolts the gap between the chassis should be 15.874"... I suspect 15 7/8" with 1 thou clearance!! however I dont know whether the fixture was designed to be tight to the chassis at this point so a wider dimension is possibly correct.

Taupe

[fussyoldfart]

Thank you Roy, and Taupe for a valued opinion and some exact information respectively.

Perhaps I am living up to my name and being too fussy. I have attempted a camber calculation based on a circle centered at the top trunnion pin. I know this is inexact in a system with unequal arms but, over short distances I hope it is good enough. Here it is:

The distance between the top and bottom trunnion pins is approximately 33cm. Using that as the radius of a circle the circumference will be about 207cm. Divide by 360 degrees and each degree covers .576cm or nearly a quarter inch. I can double that to 1.15cm on the eyebolt separation because it applies to each side of the car. So, roughly 7/16 of an inch extra will change the camber from +1 degree (for rubber bushed suspension) to nil which was the original specification for the MM. (Shop manual, general data 5).

This appears to be a much wider tolerance than I had expected. It bears out your opinion Roy and relieves my mind from the worry that a millimetre or two would upset the geometry seriously. I am "thinking out loud" and publicly here in the hope that it may help others. Also, if anyone who knows better can tell me I have my head up the tailpipe we need to make that public too!

Darrell fussyoldfart McDonald

[DAVIDMCCULLOUGH]

I would suggest refitting the front panel in place, this gives a valuable reference point for attaching the the new engine bay floor in at the right angle and you will also be able to line up the exsisting holes bolt holes with the new crossmember.

Also bear in mind that the panels may not be an exact fit, all too often they have to be trimmed to fit and sometimes even re shaped.

[chickenjohn]

I would follow Taupe's measurements and David Mc's advice. Set the chassis legs in the correct place according to measurements and gearbox x-member fit etc, bolt the front panel to both inner wings and then, if necessary adapt/modify the front crossmember to fit.

[klm]

I just read with interest the discussions on replacement of chassis legs and information on chassis dimensions. Over the past few years I have been collecting critical dimensions from various sources and my records show that the gap between the chassis legs at the eye bolt as 16 1/8". This is 1/4" more than the jig dimension given by Taupe. Does this indicate the front end fixture would have a gap of 1/8" on either side at the eye bolt hole?

I have an original front end fixture manufactured by BMC in the 50's and I am happy to provide any information if anyone hopes to fabricate one. I live in Australia and my car and front end fixture are in Sri Lanka. I am happy to obtain and provide any measurements or details when I visit there in June this year.

klm

[taupe]

Hi Klm

I think its quite possible that there should be a gap either side of the fixture when in place it is after all for 'checking' the position of the holes etc and is not intended to be an assembly jig. The jig drawing does specify for example a 1/16" gap between the fixture and the engine mounting holes (I have fitted a 1/16" steel spacer on mine between the jig and the panel) but no clearance is stated for the eyebolt holes location.

I have just measured mine with the jig in place and the jig is a snug fit between the chassis legs with perhaps a few thou clearance on one side. I have one replacement chassis leg clamped in place and not yet welded but it is an original Leyland panel... everything lined up exactly at the front engine mounts, eyebolts, gearbox crossmember and at the original main crossmember.

The gearbox crossmember is 15 7/8" wide where it fits between the chassis legs and that also fits snugly and just slides in between the chassis legs. So I reckon that 15 7/8" to 16" apart is correct though 16 1/8" may still be within tolerance.

Taupe

[klm]

Thanks Taupe for the information. I have with me two new chassis legs manufactured by HENRIC in 1989 which I guess the second best to original BL panels. During my next visit I could set up the two legs, a new front cross member and gearbox crossmember on the jig to check how it would all fit. As Minors were originally manufactured to the nearest 1/8" I agree that a gap of 16 1/8" will be within tolerance.

klm