Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 The reconditioned BVEL-BOX project is finished

Dear all

After 1.5 years of extensive research and test we can publish our M3W bevel box project.
We ourselves are flabbergasted about the results we got.

When interested please do PM me.

2025-11-04
The ‘Betty-Boop’ Bevel-box project.

“We” are a young British Land Rover Mechanic and Farmer here in France and myself [ slightly older ;-) ] : Herman.
Herman will step away out of this project after the tenth reconditioned Bevel-box.


Cause of the M3W Bevel-Box noise problems.

We have reconditioned now 3 Bevel-boxes.
We found that we nearly not had to calibrate the crown- and pinion wheels with less or extra shims.
The Timkin bearings used by Quaife are the best you can get for this purpose.
But they were all gone. Actually on all the 3 Bevel-boxes.

They are gone because of the extreme pressure of the belt-drive.
People have to tight them enormously and the rear wheel shaft nuts are tightened too with extreme force.
What everybody seems not to know is that most drive belts nowadays are reinforced with Kevlar.
Because the belt is so tight it gets extremely hot.
The temperature coefficient of Kevlar is negative, so the belt is even more tight with that heat.
https://www.linearmotiontips.com/wh...ed-belts-for-linear-motion-applications/
“Although Kevlar is suitable for a wide range of temperatures, it has a negative thermal coefficient of expansion, meaning that it shrinks as the temperature rises and lengthens as it cools. Since this behavior is the opposite of most other machine components (especially those made of metal) — which expand as temperature increases and contract as temperature decreases — Kevlar-reinforced belts may not be suitable in environments with significant temperature fluctuations.”


Bearings have a small toleration for tangential forces, so you are ruining them.
The chain drive protects you against this. When not using the car there is no pressure on the bearings And when idling - and that’s half of your driving time - there is also no tangential pressure on the bearing.
With a belt - when not driving - you are still pressing all the oil out of your bearings and when you go out for nice drive - for at least - the first km's you have dry bearings.

The other problem with the driving belt is that also the rear wheel bearings and the swing arm bearings get far too much tangential pressure. So you have to renew them also more often.
 

Leaking oil seals
The stories about are very simple to be answered.

The problem is the quality of the standard oil-seals used.
Standard oil seals will break down at max 80 oC.
Viton - the simple ones – to max 130 oC.
The top quality Viton to 220 oC.
The bevel box gets temperatures of 120 oC easy under power and 85 oC till 95 oC when driving. I tested this for the last 2 years.

Tests and temperatures
I am flabbergasted about the result of our reconditioned bevel-box .
The extensive driving tests showed us that we have no noise any-more.

The 'recon' has a lot lower temperature, driving cruising speed not climbing mountains : 65 oC to 75 oC.
That temperature difference explains also a lot.

We Installed a kind of air duct, which reduced the temperature most of time with > 30 oC., of course depending of the tarmac temperature.

I also tested thicker and more oil. ‘Amsoil 250 severe gear’.
Cooling is far better and the bearings are always at least half in oil.
Too much oil will not ruin the oil seals.
I experimented - for more than a year and over 12.000km - till 800 ml and never got any foam. I can easily see the building up of foam because I installed a separate filling tank.

Pricing
We found that doing a reconditioning of the bevel box is now in 2025 possible for around € 2550,- , materials, time , transport back etc. included
All prices are without VAT.
We cannot work with VAT because it is small French company. And like to keep it like that.


So we will offer a reconditioned Bevel-box to M3W owners.


When you send your 'to be reconditioned' Bevel-box :

You : The client
Has to make a strong wooden transport crate by yourselves. This crate will also be used for returning the Bevel-box.
Has to pay an advanced payment of € 1000,-
In case we can work with the send Bevel-box the advanced payment will be calculated in the final bill, which is for the first 10 Bevel-boxes - upon may 2026 - € 2550,- as mentioned above.
When we cannot work with it we will send your bevel-box back when you want and take some labour-time and post cost - around € 360,- - from that advanced payment. Or give the option to sell it to us to use good parts.

Standard :
- We deliver the Bevel-box back with the original top hole - BSP 3/8 - and close the side hole.
- We will give you a work report with pictures of the internal alignments
- We will only use the Viton with a toleration of max 130 oC when extra cooling is possible.
- We will do a 400km driving test.
- We will give a quaranty for silence for 6 month after return-delivery. [ Not included additional transport costs. To be paid by client ]
- In case you do not want to lose time on this project we will return an already reconditioned bevel-box [ ask for availability ] . So the returned will probably not exactly being the same which you have send. ( Normally we should have 2 tested Bevel-boxes in storage )
When the client asks for exactly the same bevel-box back, this will be possible but the reconditioning will take several weeks more time.
- We will use the old Quaife crown-wheel and pinion nuts.
When necessary or asked by client we can install new ones for € 100,- including a removable dust-stop – rear swing arm plug - for the left swing arm bearing.
Standard it seems there is only one dust-stop installed, but you need two to protect both bearings.
The new nuts are different from the original ones.


We advise to buy and install the following :
- A black aluminum filling tank with hose, support and fittings of 1 liter to make filling of the 750ml more easy and also to be used as a better air vent.
We can deliver : Extra costs around € 250
- Using Amsoil 250 Severe Gear oil and around 700cc
- A three wire PT100 thermocouple to be installed in the former filling hole.
We can deliver and install : Additional costs € 35,-.
Because everybody wants his own PT100 gauge for this, you have to buy and install it yourselves.
- “Stahlbus oil drain hole”.
We can deliver and install : Extra costs around € 65,-
This drain-system will make taking out the oil at oil-changes much easier and controlling the oil-level too.
- Getting Phil-Bleazey bevel box support, because it will cool the Bevel-box much better.
When necessary we have a modification for a more simply aligning of the bevel-box.
- We sincerely recommend but it is your own choice getting your Phil-Bleazey chain drive conversion kit. Remember an extra chain-oiler is necessary, you do not want to this by hand every 400km.
- 2 front rear wheel adjusters. To keep the rear-wheel in place and always be aligned.
Front adjusters are important. I drive now for a year with them - my own design - and I never have to tight the rear will nuts extremely tight and the wheel stays always aligned.
Taking the rear wheel out is simply done by taking the wheel shaft - spindle - out.


example of a reconditioned Bevel Box


Bevel-box-support-alignment and air duct


example of rear wheel front adjuster


Aft with temperature sensor and drain device


fittings to external filling tank and side stop in steel


fittings to external filling tank and side stop in steel

Good arguments for the chain conversion!

A very interesting and informative set of ideas on improving the original design, all of which seems very fitting relative to the expectations of both Morganeers and Morgan management/design of times past..?

Many thanks for providing such a detailed insight to your processes of bevel box improvement...

Herrie - a few questions if I can, as this is very interesting... and congratulations on your success!

1. When you say "We found that we nearly not had to calibrate the crown- and pinion wheels with less or extra shims" - do you mean you almost always had to change the shims? or that you found that wasn't the problem?

2. You also mention the bearings problem, which I can quite believe. But I don't understand your solution for belt-driven rear wheels: do you recommend just slackening the belt? I often wondered if a belt tensioner arrangement should be used. Or is your solution the increased level of oil in the bevel box to enable more oil to the bearings when the vehicle is stopped? I would expect (from your explanation) that the bearing change on the BB should be a regular service item.

3. I like the idea of your bevel box alignment rod. I remember asking Phil B about correct lateral positioning when I installed his bevel box mount.

4. I recall Emil / MorganCustom in the USA offered a bevel box oil cooler. I could not recognise your air scoop from the photo but it might be the extension to the bevel box mount to the transverse chassis rail? [My impractical thought (as there is probably no room!) would be to follow the German solution to Fw190 radial engine cooling in WW2: mount a little fan over the belt output to blow air over the bearing!]

5. Also on the recommended header tank for BB oil: is the idea that the BB is full of oil and the header tank is for expansion? Would be good to see where you suggest this is fitted - I would assume mounted against the back bulkhead under the luggage panel?

Many thanks for any reply!

Yes, Emil did offer a Bevel Box oil cooling kit I have one installed and it does help. I turn the pump on before moving off to give the bearings a spray it also increases the oil capacity up to the breather level you can see the level in the feed pipe. Maybe I should try taking the breather out block it off and fill it to the 700cc its currently at 420cc as the fill pipe has a breather on the end which would relieve any pressure.

From PaulV

Herrie - a few questions if I can, as this is very interesting ... and congratulations on your success!

My answers :
Of course here are some answers but unfortunately it became a long story to answer. Sorry for this.
We did a lot of research and a lot of tests to get this project done.

1. When you say "We found that we nearly not had to calibrate the crown- and pinion wheels with less or extra shims" - do you mean you almost always had to change the shims? or that you found that wasn't the problem?

Yes, we had to take out the old shims, but it is very important that we have to keep them apart – of both sides – so you know which were installed where.
But cleaning and controlling them with the crown-wheel teeth was most of the time enough. We bought several very thin new shims which we used for fine-tuning, we needed them.
But this part of the job was – unexpectedly - the least work after all.

2. You also mention the bearings problem, which I can quite believe. But I don't understand your solution for belt-driven rear wheels: do you recommend just slackening the belt? I often wondered if a belt tensioner arrangement should be used. Or is your solution the increased level of oil in the bevel box to enable more oil to the bearings when the vehicle is stopped? I would expect (from your explanation) that the bearing change on the BB should be a regular service item.

This is a more difficult topic to answer and has costs us the most research time to understand the problem and to be sure we were on the right track.
It is also subject to a world of discussions within the M3W family.


The belt drive
In our opinion the belt drive is the main reason for all the trouble.
I. You have to tight it too much. In that case there will be always enormous pressure on all bearings, not only the bevel-box bearings but also the rear-wheel and swing-arm bearings. And this pressure creates heat and ‘wear and tear’.
But the problem of the Bevel-box bearing is that you create a tangential very small bearing load-zone.



Timken : “The arc defined by the rollers supporting the load is called the bearing load zone. The load zone is significantly influenced by bearing setting or internal clearance, either radial or axial depending on the bearing type.”
“ A larger load zone gives longer bearing life.”
This drawing of Timken tells enough.

I made the conclusion that the bigger the load-zone the longer the bearing life.
With the high and tight axial pressure due to the belt drive you create a smaller load-zone: Just a few rollers will take all that the pressure-force.
And explains herewith why the life of the bearing in case of a belt drive is far shorter then with a chain-drive.

II. The other problem is that with that extreme tight drive-belt the tangential friction on the bearings will create heat too.
Timken :
“When heat must be carried away from the bearing, oil must be used. It is almost always preferred for very high-speed applications.”
Timken :
“HEAT DISSIPATION
The heat carried away by a circulating oil system.
In a splash lubrication system, cooling coils may be used to control the bulk oil temperature.”

III. With the current - only rear-wards - alignment possibility the rear wheel tents always to switch to starboard. How tight your turn the Spindle nut at the end you will always find after a while a slightly looser rearwards-adjuster at starboard.
Which will always give mis-alignment between the bevel-box-sprocket and the rear-wheel-sprocket. And which creates again extra friction and so heat with all the consequences.

IV. The oil is pressed out the teeth of the crown-wheel when you are not driving.
And because our M3W’s are fun trikes they do not make much mileages. So the time the rear-wheel is not turned, at the same time the oil will still be pressed out of those teeth. Not with a loose chain.
Do not forget that even MMC has changed the belt drive on the super-3 back to chain drive. And on motor-bikes it is only used in ( HD ) touring bikes. Even the nice Polaris-trike which have far more torque than our M3W uses a chain-drive.

So we do not recommend slackening the Belt-drive, because it will skip on his teeth.
When owners want to continue with a belt drive they should do, but not be surprised that the whining issue comes back after ??? miles.
A belt tensioner is not strong enough to handle the necessary torque on the belt. The teeth of the belts are too short.

Conclusion out of I , II, III, IV :
Actually the case is that you should get rid of this belt-tension, which seems to me is - with our current knowledge - not possible.
That’s why I installed a Chain-drive.

- The increased oil
Increased oil has more than one reason.
Frist it cools better and cooling the Bevel-box is very important.
I made an extra dashboard to check interesting temperatures and I have measured quit high temperatures in the Bevel-box. Even to a level that standard oil-seals cannot handle it.
Increased oil volume keeps also minimal half of the crown wheel teeth constant lubricated. The advised 300 cc does not even nearly lubricate the lower teeth, only by splashing.
Think about this when the M3W is not used for a period.

- Changing the bearings
This should not be a regular item as long as you keep the temperature low, half of the Crown wheel teeth lubricated and the mean bearings also at least half lubricated, like actually is the case at nearly all car-differentials I know.
But that said . . . Having a belt will damage the bearings of the Bevel-box, rear wheel and the swingarm faster than with a chain-drive.
All the moments you idle – which is approximately half of the time you drive - with a chain-drive and when the M3W is not used there will be no pressure at all on all of these bearings, with a belt always.


3. I like the idea of your bevel box alignment rod. I remember asking Phil B about correct lateral positioning when I installed his bevel box mount.

I found it necessary.
I changed already the design of the Bevel-box alignment device to a smaller and stronger version.
But for the same reason this alignment is necessary for the Bevel-box it is for the Rear wheel too.
In combination with the Bevel-box alignment device a Forward rear-wheel adjuster is in my opinion a very important device too.
You really have to see those in combination with each other.

And . . . this especially interesting for those who have a Belt-drive.
I am working on an article about this issue and will soon publish it.


4. I recall Emil / Morgan-Custom in the USA offered a bevel box oil cooler. I could not recognize your air scoop from the photo but it might be the extension to the bevel box mount to the transverse chassis rail? [My impractical thought (as there is probably no room!) would be to follow the German solution to Fw190 radial engine cooling in WW2: mount a little fan over the belt output to blow air over the bearing!]

- Emil
Yes he was a great inspiration for me. Unfortunately I could not ask him questions anymore.
My main question would be :
“Did you only make a oil-cooling device or did you also checked the interieur mechanics of the Bevel-box ?”
Because without the latter a cooling device will not help much. It is only a ‘symptom management’ but the cause of the heat is still there when you do not change the mechanics of the bevel-box.
And it seems to me that it is too complicated and too vulnerable.

The answer of Britmog/Bruce on TM - #837217 - is very interesting
“Yes, Emil did offer a Bevel Box oil cooling kit I have one installed and it does help. I turn the pump on before moving off to give the bearings a spray it also increases the oil capacity up to the breather level you can see the level in the feed pipe. Maybe I should try taking the breather out block it off and fill it to the 700cc its currently at 420cc as the fill pipe has a breather on the end which would relieve any pressure.”

This is exactly what you have to do. I think the 700cc or 800cc would do the same splashing when you start driving the first 20 meters slowly.
But keep in mind my foam-comment at : “The extra lub-oil tank”

As Timken writes : “In case of a splash situation you need extra cooling coils”.
This is not possible in- or outside the current Quaife Differential box.

Air-scoop
Perfect alignment of the Bevel-box with the rear wheel, changing the bearings, using more oil ( 800cc instead of 300cc ) and the air scoop, is far more simple to do with the same cooling results.
I made just a simple scoop, and from several other owners I understood they had created something with the same idea.
But . . a scoop has only use when you get rid of the standard NVH kit.
You can see the air-scoop just in front of PB’s Bevel box mount. I suppose I have to change them maybe every 2 years because of the dents of ground contact. I can lift the car with my suspension, but still . . .
I make them very cheap of standard rectangular Aluminum U-Profile.

For me I got the temperature around 30 degr. C lower with that simple scoop.


5. Also on the recommended header tank for BB oil: is the idea that the BB is full of oil and the header tank is for expansion? Would be good to see where you suggest this is fitted - I would assume mounted against the back bulkhead under the luggage panel?

- The extra lub-oil tank
The main reason is a more ‘simple’ filling system for the Bevel-box lubrication oil. ( It takes some time with the tank and the long Hydraulic ( metal sheeted ) hose with the thick 250 oil I use )
I also could check with the tank during my test periods if the oil was foaming. With foaming the foam will easily build up in this tank and else not.
Foaming tells me there is too much oil, or too hot. But when occurs the lubrication is not working properly anymore.
That’s a point you should consider when putting more oil in the Bevel-box.
Yes, it is at starboard under the luggage panel ( Boot inner tray ) against the back bulkhead panel.
I attached it on black fiber board so you can easily take it away and I used a solar-panel ‘roof cable-inlet’ to cover the hole I made in the ‘Boot inner tray’ to get the oil-line through.

Re the M3W drive belt tension, a good rule of thumb is to set the belt so you can twist the lower run about 45-90 degrees.