1962 Lotus Seven Radius Arm

[TEM]

Hello All,

 

Same car different problem.  While investigating the rolling issue I noticed the u-joint connecting the prop shaft to the diff was hitting the A-frame cross bar.  The diff input shaft was not parallel to the ground, it had a distinct nose down attitude.  The suspension U-bolts were also leaning forward.  I found the right side upper radius arm was damaged, bent over where the natural bend occurs.  Not sure of this is my only problem but this radius arm will need to be replaced.  Does anyone know where I can source one of these?  Does RDent or DB carry Seven parts?

[SENC]

Check with Tony Ingram at lotus7.com and with Chris Mintoft at Redline in the UK.

[TEM]

Thanks, will do.

[MV8]

Adjustable length (on the straight, forward end) would be nice for pinion angle adjustment. If you can't find one or a set, new can be made from the old ends or just used as a pattern, with known, good eye to eye measurements.

 

Here is a pic of a good upper arm.

Edited September 25, 2023 by MV8

[IamScotticus]

Heh, its on upside-down 

Edited September 30, 2023 by IamScotticus

[MV8]

[IamScotticus]

OK, ive seen otherwise.  

I think it was S1

Edited September 27, 2023 by IamScotticus

[TEM]

Why is there a bend in the arm?

[TEM]

Thanks MV8 for the picture, very helpful and a beautiful car!

 

I see that the axle U-bolts are not perfectly vertical.  Is the diff input shaft horizontal to the ground or does it have some small upward angle?

 

Found a new set from Chris at Sevens & Elans.

[MV8]

Yes it is but it is just a photo I found. I don't own a Seven.

 

The bend maximizes clearance to the U bolts that changes in cornering roll.  

 

I don't know what the operating angle is but I would expect it is probably supposed to be parallel to the transmission output shaft. Ideally it should be less than 1.5 degrees and the same at both ends of the driveshaft to prevent velocity changes with each rotation.

 

A digital, magnetic base angle finder is about $13 on ebay. Since the axle perches are fixed/welded to the axle tube, the only way to adjust the pinion angle (directly versus trans mount shimming) is with arm length. I don't know that anybody bothers to check or adjust. May be fine with good arms.

Edited September 26, 2023 by MV8

[SENC]

13 hours ago, TEM said:

Thanks MV8 for the picture, very helpful and a beautiful car!

 

I see that the axle U-bolts are not perfectly vertical.  Is the diff input shaft horizontal to the ground or does it have some small upward angle?

 

Found a new set from Chris at Sevens & Elans.

 

Remember that the axle is unloaded in the picture, so that bit of angle should be expected.  Once the car is sitting on its wheels and carrying weight it should be approximately horozontal, allowing some movement in the vertical plane in either direction. 

[TEM]

Good point on the axle being unloaded.  I'm sure when I get the new radius arms on that the alignment issue will be solved.  Not looking forward to pulling and disassembling the axle though.  Pulling the drive shafts out sounds like a nightmare.

[IamScotticus]

The removing of axles and pumpkin don't require special tools and come out without too much effort.

Its the disassembling of those sub assemblies, like bearings from the shafts and changing pinion, crown gears and differentials, that require the special tools.  You shouldn't have to do any breakdown for a refresh and bearing greasing.

If the brake cylinders have been sitting for ten years, check those bores for rust.  Have a tube of brake grease ready for the reassembly if you get lucky.

Get a tube of black silicone sealant for the hub mount and back plate sealing.

 

Theres a neat product , Quick- Glo, for rust removal and polishing.  good for spot cleaning and parts like the Park brake rod.

It comes in different grits and leaves a protective wax coat.

 

Edited September 30, 2023 by IamScotticus

[TEM]

Looks like an interesting product but the company appears to be out of business and the product seems to be only be available on ebay.

[fotsyr]

Nice copy of the photo of the BRG 7 that I am restoring. 

[TEM]

Yeah, I don't think that one is going to buff out.