Mutocel and Underfelt in (later) XK 120 OTS

Bob_K1 · November 28, 2022, 10:36am

The subject has been partially dealt with on this Forum, but still some questions remained unanswered. I dug a bit deeper and found more information. It’s not enough for an article in one of the magazines, so I put it here for “those interested”.

Mutocel over Gearbox Cover.
Jaguar XK 120 SPC J.11 (1958) refers to Mutocel BD.3864 with suffix 6 to 12, as the five pieces of Mutocel required for the insulation of the early Gearbox Cover BD.3168. Only two pieces of Mutocel BD.4596/7 are required for the later Gearbox Cover BD.4078. The latter pieces of Mutocel measure 32” x 30” (81 x 76 cm) each, according SPC J.11 (FHC) and J.13 (DHC). .

Urs Schmid shows the (later) Gearbox Cover BD.4078 with the original Mutocel pieces. One is placed on the outside and one on the inner side of the Cover: cuts have been made to obtain the right shape. Bifurcated rivets are used as an extra measure to keep them in place.
Underfelt is placed over the Mutocel.

Although not mentioned in the SPC’s, Mutocel was also used on the inside of (later?) doors: a longer strip of about 16” long and 6” wide was used along the top of the door (partly behind the horizontal section). In addition, at the inside of the door panel a piece of underfelt of about 6” x 12” was glued in the centre.

Mutocel was a “sound deadening” material manufactured by the Ruberoid Company, originally from the USA but with activities in the UK as well. Mutocel was developed in the 1930s and used by a number of British car manufacturers. Mutocel is described as “consisting of several layers of felt, bonded together with bitumen”. See example as presented by Wolseley for their 1937 model “12”.

Note that (unlike modern similar materials) Mutocel didn’t have a self-adhesive back, but was glued to the panels to be covered.
In Europe similar materials (with the same “diamond” pattern) are supplied by various companies like 3M (08840), Terodem/Teroson (by Henkel), Dinitrol (by Dinol/Würth) and many others.

Underfelt for XK 120 OTS
Three pieces of underfelt are used (according the SPC) for the XK 120 OTS (see photo below).

The piece in the middle (coded BD.4596/6), fits over the gearbox tunnel and measures 32” x 30” (81 x 76 cm). The other pieces are for the toe boards: BD.4589 for the RH side and BD.4590 on the LH side, the latter having a cut out for the dipper switch. All part numbers related to LHD cars. Unlike the FHC and DHC, the OTS had no underfelt underneath the floor carpets.

We already mentioned the piece of underfelt used on the inside of the door.
The “Panel for Lubrication of the Propellor Shaft” (as used from December 1952 onward), bolted to the side of the Gearbox Cover BD.4078, had a piece of underfelt cut to the correct shape (see very first photo).

Bob K.

XK-SS · November 28, 2022, 2:55pm

If you check the gearbox cover carefully, you will find the holes where the inner (underside) sound deadening was attached with split rivers. Photos show alloy gearbox cover but steel cars were the same,

Original material was about 1/8" thick, stiff but moldable and rubbery. I used thick roofing felt as a replacement.

Bob_K1 · November 28, 2022, 3:56pm

Thanks for your reaction and additional info regarding the early (alloy) cars
Yes, I’ve seen the small holes on various places on the Cover where the “bifurcated” rivets were positioned. See also pic below with some holes in the Cover of my 1954 OTS.

It is clear that the first 184 cars used 5 different pieces of Mutocel for the early Gearbox Cover like you show But are you saying that this “Mutocel” arrangement was continued on the early steel cars as well?

The photos that Urs Schmid shows in his book “Jaguar XK 120 The Anatomy of a Cult Object” are of a “post December 1952” Gearbox Cover and has a single piece of Mutocel on the outside of the Cover.

Bob K.

XK-SS · November 28, 2022, 7:51pm

Bob,
I am fairly certain the material was used both inside and outside the gearbox cover on all 120 models 49-54. I am not so certain about the 140. Photos from I believe a 52.

Bob_K1 · November 29, 2022, 9:45am

Yes, that would make sense. The dimensions of the 2 pieces of Mutocel are far too big to cover only one side of the Gearbox Cover. So both sides are covered with Mutocel, most likely glued and with the bifurcated rivets as an extra measure to keep them in place.
I’ve changed the text of my original contribution so any reader that will read this item, won’t have to check for any changes made later in the discussion.

Bob K.

Rob_Reilly · November 29, 2022, 7:33pm

Ruberoid, wow how did you find it?
I searched all over the web and couldn’t find anything about Mutocel.
Here is an advert from Grace’s Guide dating to 1907.

However, there is no mention of Mutocel.
https://www.gracesguide.co.uk/Ruberoid_Co

Bob_K1 · November 29, 2022, 8:15pm

Rob,

I had the same problem: couldn’t find anything on Mutocel. Until I found an article related to Loudspeaker Boxes of the 40’s and 50’s and their wooden housings. They used Mutocel to avoid certain resonances. In particular the British brand Wharfedale provided information on “how to build you own Speaker Box” of course on basis of Wharfedale loudspeakers. See here:

Than all the pieces started to fall in place. But also a brochure of the Wolseley 12 (1937) had a reference towards Mutocel, although they refer to “Mutocel on top of noise-deadening compound”. May be the author didn’t fully understand what he was writing.

As I said, Ruberoid (US) became also active in the UK in the 1930s and possibly Mutocel was even developed by Ruberoid UK, hence the lack of information in the USA.

Bob K.

Bob_K1 · December 1, 2022, 6:27pm

As an update, I show these pics of my Gearbox Cover with a new layer of “Mutocel” or better a modern replacement. The material is so new and shiny that it looks more like I have a “carbon fiber” Cover. But the “Mutocel” will “age” quickly without doubt.
As I couldn’t find a piece of 32 x 30" that would match what Jaguar used, I had to use smaller sizes which nowadays are either about 10" x 20 or 20" x 20". In both cases I have to accept that there will be lines visible between the individual pieces.
Still had some “Bifurcated” rivets and will use them. See second photo.

Bob K.

Kendoo · December 1, 2022, 9:25pm

Bob,

You have now set the standard for restoring the gerbox cover. That is no doubt better than new.

Bob_K1 · December 2, 2022, 9:27am

Thanks Matthew,

But there’s always room for improvement: I copied the cut-out section for the access panel at the top from the one in the underfelt (new), but that was wrong as the opening in the “Mutocel” is much smaller than the one in the underfelt. You can see the hole for another Bifurcated rivet that became now meaningless.
See also the pics from Mike (XK-SS) of the Mutocel at the inside of the Gearbox Cover.
Better next time…

Bob K. ,

Tunnicliffe · December 2, 2022, 3:49pm

Mutocel: Just to add fuel to the fire, my 1946 edition of The Trader Handbook lists Mutocel (anti-vib, strip) as a proprietary name belonging to Gliksten Bldg. Materials.
Earlier and later years fail to mention Mutocel, but the 1947 edition does list the address of Gliksten Building Materials as Carpenters Road, London, E.15 (phone: Amherst 4444).
BTW The Trader Handbook was an annual “Legal, Technical and Buying Guide for the Motor, Motor Cycle and Cycle Trades”, published by ILIFFE.
Chris T.

Bob_K1 · December 2, 2022, 6:39pm

Chris,
Tried to find more on Gliksten Building Materials but everything is pointing in the direction that this was actually a large company trading in hardwood products. They also supplied these materials to the (pre-war) Britsih automotive industries.

During the 1961 Building Exposition in London, Gliksten mentioned that the following companies were part of their enterprise: see picture below

Is it possible that the company is mentioned because they sold Mutocel but were not the actual manufacturer?

Bob K.

Bob_K1 · December 2, 2022, 6:56pm

Did the inside of the Gearbox Cover today and also placed all the Bifurcated Rivets. Made the opening for the gear lever a bit smaller at the inside (see picture).With the Mutocel on the in- and outside, the weight of the Gearbox Cover has increased by at least 4 kg (8 to 9 lbs)…

Later in the afternoon I installed the Gearbox Cover in the car: fitted well. See picture of the area around the accelerator pedal. Note that the picture is a bit distorted due to the close distance of the camera. Tried to use the original round-headed slotted screws as much as possible.

Question: why isn’t there any seal behind the accelerator pedal? Although the bracket is a kind of closed box held by 4 screws, it certainly is not a closed box and water might enter via the accelerator mechanism.

Bob K.

Tunnicliffe · December 2, 2022, 7:57pm

Bob, I completely agree that the problematic Gliksten ownership raises more questions than it answers. I tossed it in though, because Trader Handbook is a pretty reliable source of period manufacturer data.

Is it possible that the company is mentioned because they sold Mutocel but were not the actual manufacturer?

Most unlikely because it’s a directory of manufacturers, not motor factors. I cannot explain the link and am very happy for the tenuous connection to be ignored until it can be proved reliable.
Chris T.
P.S. Loving the look of your tunnel.