Hangar works #18 – Soundproofing and sealing the cockpit

Yes, we know it: the Morgan 3-Wheeler is a noisy car. Nothing strange, as it’s a fully open cockpit powered with a huge V-Twin 2 litres engine with loud exhausts. In fact, this is precisely one of its charms. If you buy such a machine you can’t complain about the noise it makes!

However, it has some parasitic noises that are not so attractive. Once you know your 3-Wheeler, your eustachian tubes start to detect them. Here and there, a rattle, a clonking, a rubbing, a squeaking… We have a permanent battle against metallic rattles and vibrations. The difficulty to cancel these is to find the source. But once you find it, these kinds of noises are easy to solve. With a little effort and persistence, the 3-Wheeler stops sounding like a maraca.

Then there is the most famous noise: the bevel box situated just behind the seats.

For those who are not familiar with the 3-Wheeler powertrain, the bevel box is a simple gearbox that transforms the movement of the transmission shaft into the rotation of a pulley at 90º on which the transmission belt that goes to the rear wheel grips. Here below you have a nice scheme of the 3-Wheeler’s transmission (built 2014 and on), with the bevel box in the red circle.

Some describe the bevel box’s sound as a whining, others as a howl, or like a whistling… Others say they don’t hear it at all… It depends on every car, and I guess it depends on the pilot’s eardrums too. Some bevel boxes happen to be much noisier than others, without a clear technical explanation, but don’t get me wrong: the bevel box’s noise, if you can hear it driving your 3-Wheeler, is not as loud as a WWII air raid siren. It is a permanent white noise, inherent to its mechanical characteristics and design, and many are not bothered at all with it.

Some owners try to reduce it using different methods, such as an oil type / brand change or filling it to a different oil level, with more or less success. But it’s a noise that can’t be fully cancelled. Fortunately, in our 3-Wheeler it’s quite discrete; or at least we don’t notice it that much.

The most common way to reduce this bevel box noise, and many others, is to do a proper soundproofing of the cockpit using sound and vibration absorbing materials. The most popular is the Dynamat Extreme. It’s defined as “a light-weight, elastomeric, butyl and aluminum constrained-layer vibrational damper“. You can find it very easy on the Internet and acquire enough sheets to line the 3-Wheeler’s cockpit for less than 200 €. In our case, I bought three packs of what the brand calls “door kits”. Each one has four sheets of 910 x 300 mm. It showed to be more than enough!

There is another task to do once you remove all seats and panels. And it’s as important as the soundproofing; or even more in my personal opinion: to seal the cockpit.

What do we mean by sealing? The Morgan 3-Wheeler cockpit suffers from permanent ingress of dirt, and water when it rains, because there are gaps between the panels. So, the dirt and dust (and water) lifted by the rear wheel and the aerodynamics of the car sneak into the cockpit through these gaps. It’s not a major issue, because the dust getting into the cockpit is little. But little by little, it becomes a lot… To seal the larger gaps, I will use a 10 mm thick and 50 mm wide very dense neoprene self-adhesive tape. This material is more resistant than any other kind of foams, and it lasts and repels water much better. For the thinner ones, I’ll use a classic self-adhesive aluminum tape. The combination of both tapes will dramatically reduce the ingress of dirt and water into the cockpit, according to the comments in the Talk Morgan forum. We hope so!

Let’s go to work! I come down to the garage and download the 3-Wheeler from the trailer where we keep it safe. I move our SUV to make room for the Morgan between it and the trailer.

For this occasion, I have a new toy: a superb 50W LED working lamp on a telescoping tripod. If you plan to do any job in a garage as I do, I recommend you get one of those!

The first easy task is to remove the seats and mats. A small portable vacuum cleaner and some wet rags to clean the floor, and we’re ready to continue with the dismantling of the backrest and the propshaft cover.

The backrest of the 3-Wheeler is made in two pieces. To take them out, you need to remove the four M6 screws that fix the upper part from behind the upper closing panel where it lies on. And to access them you must first remove the boot tray. Easy task. All screws are accessible. First surprise: our four M6 bolts of the upper backrest are very loose. So loose that their big metallic washers move quite free. This was a source of a metallic clinking for sure! One more detected and solved (while all back in place).

The second step is to unscrew and remove the seat belt buckles from the side panels. Otherwise, it won’t be possible to take out the lower part of the backrest.

Then, the way I take out the backrest is as follows: gently, I pull forward the down part of the lower backrest while I punch downwards its upper part. The lower backrest then, little by little with every punch, tilts and slides down and forward-out. As you see in this next picture, this maneuver is to liberate the two aluminum plates screwed to the lower backrest, that are inserted behind the upper backrest.

After removing the lower backrest, again with gentle punches I push downwards the upper backrest, so it slides out as it is wedged between the rear upper closing panel and the body profile. Now the seat bulkhead panel (lower part) and the upper closing panel (upper part) separating the cockpit from the rear wheel area are totally visible.

In my car, built in December 2019, I can see that the Morgan Motor Company has already put a sound insulation kit over the seat bulkhead panel, to reduce the famous noise coming from the bevel box that is just behind it. It’s a hard layer of dark grey material. I ignore what is it, but it’s nice to see they’re improving and trying to solve known inconveniences.

At this stage, I could stop removing parts and panels, and simply put the Dynamat sheets over the floor and the visible panels. But I want to do a reinforced soundproofing and sealing with the neoprene tape as many gaps as possible. So, I keep removing parts, such as the propshaft cover, the seat bulkhead panel, and the lower side panels. Of course, cleaning as much as possible during this process is mandatory. Now the interior is ready for a deep soundproofing and sealing!

The first piece I work on is the detached seat bulkhead panel. I put Dynamat on both sides. Even over the factory sound insulation kit, because this is the panel that gets over the bevel box.

The Dynamat Extreme sheets stick to any clean surface really well. In fact, the product is so sticky that you have to be wise and very precise while putting it! You need to measure the surface and cut to shape the sheets with high precision. Using paper or carton templates is the best way to assure you don’t do a mess over the difficult surfaces. Because if you make it wrong, removing a sheet is not easy and will leave a mess of black sticky paste on the surface.

To work with these Dynamat sheets, you’ll need large scissors and gloves. Be careful with the edges! The aluminum is very thin and sharp. You can easily cut yourself if you don’t wear gloves.

The result on the seat bulkhead panel is very satisfactory. The Dynamat sheets are flexible enough to adapt to curves and edges. However, I prefer to cut some specific pieces out of them, for very precise spots of this seat bulkhead panel, as its shape is complex just where the bevel box is covered.

Now it’s time for the propshaft cover. I put two layers inside this cover, as there is enough room for it, and because this tunnel is open on both ends to the front (gearbox) and rear (bevel box) areas below the car. So, air currents carrying dirt and water can ingress this area. The Dynamat layers will reduce the noise and protect the piece against this dirt and possible water ingress.

Now I come back to the car. It’s time to cover the grooves through which dirt and water seep into the cockpit. Neoprene thick tape in hand, I start filling the big ones. In some cases, I need to put a double layer of this neoprene tape! In the following picture you can see that just behind the seat bulkhead panel, you can see the tarmac below.

From there, the dirt can ingress between the side panel and the aluminum body through a massive gap. Here below you can see I blocked this gap with the neoprene tape, sticking two layers one over the other and applying pressure to insert them there.

To fill the grooves between the edge upper closing panel and the body, I continue using the thick neoprene tape. I manage to block almost every gap around its edge. This tape is really useful and seems to be really tough. I hope it lasts for long.

After looking for every little gap, I come back to the Dynamat. Time to do the floor. It’s probably the easiest area as it’s flat and the shapes are almost rectangular. Few cuts with the scissors and the floor is done quite fast.

Only the area of the front mat on the pilot’s side takes longer, because I have put some industrial 3M Velcro strips to avoid the mat moving around in front of the pedal set. So, I have to cut small pieces of Dynamat to be fitted in between the Velcro stripes.

The last areas to be covered with Dynamat sheets are the upper closing panel and the sides. Cutting first some carton templates, the upper closing panel is relatively easy, and I use the aluminum tape to make sure the very thin grooves around it are sealed. I avoid overlapping the seat bulkhead panel, so it can be removed for maintenance without damaging any Dynamat area.

The inside of the body sides are probably the most difficult parts because they have an angle rear side, the two plates and bolts supporting the exhausts, and a chassis vertical bar at the front. I manage to make those with a single long Dynamat sheet. I first cut the sheet to the exact shape, then cut holes for the nuts, and finally stick it sliding very carefully the sheet between the front vertical chassis’ bar and the aluminum body panel. A delicate move with such sticky material!

With all soundproofing and sealing works done, I re-install all panels, backrest parts and seats. It is relatively easier than dismantling them. The whole process, working alone, took me about seven hours.

Looking at the cockpit with all back in place, you can’t notice any of these works.

Then we take the Morgan for a test drive. And we can’t be more satisfied! It really works! The car is truly more silent. This improvement is one of the best we’ve done!