35 replies to this topic

[carlt]

Hi ,

I am restoring / re engineering a 1956 Buckler MK15 for Hillclimb and sprint use http://www.bucklercars.com/

It is a multi tube spaceframe [ Lotus 7 esq. ] using the original Morris Minor running gear . I will try and post some pictures ,[ not always successful with my limited IT skills ]

I am replacing the rear leaf springs with a multi link set up ,
the chassis lends itself to lower trailing / upper leading links [ lateral watts links ] picking up on the original leaf spring mounts ,
but with the addition of a pair of diagonal chassis tubes incorporating suspension pick up points , I will be able to run twin trailing links as an option .

The chassis is also almost ready made for a Mumford link as lateral location

I have a reasonable understanding of the basic theory and some experience of live axle location on these types of car ,
I modified my Lotus 7 to win the British hillclimb class championship twice in the early '90s [ long trailing links , sliding pillar 'A' frame ]

I have read as much as I can find , and observed various Mallocks on the Hillclimb scene over the years

I would like to find some detailed information on the later Mallock live axle location ,

I have read the threads on here where the subject of Mallock Trailing Arm Magic and the Mumford link has been mentioned ,
Bill Sherwood and Cheapracer talk about reading up on the subject http://forums.autosp...w...05210&st=80
I would really like to know where to read up on these subjects
Input greatfully recieved
Cheers
Carl

Edited by carlt, 29 August 2009 - 21:41.

[Bill S]

It's pretty hard to find anything much at all on the Mumford, but they aren't too complex fortunately.
The TAM gear might be a bit easier, I haven't looked sorry.

I've got a Mk31 here at home, the last of the front-engined Mallocks and the final iteration of TAM.
It's odd, but on an identical car I've seen it in action and it works very well indeed, although over a relatively limited amount of wheel travel.
Also, as I tell the various people that want to fit a Mumford to the rear of their cars, you really need a good reason to, because it'll give you a very low rear roll centre and so unless you have an equally low front RC you're going to end up with an unpleasantly handly car.
The rest of the TAM gear is more transferable to another car though, as it's just a matter of getting the trailing arm links in the correct place. And they're a little odd as well - Three of the four are pretty much as you'd expect, but the upper-top link is mounted on the inside of the chassis and the spherical ball joint on the front of the link is setup so that you can put the locating bolt in, then you wind the joint in half a turn and grunt a little to get the bolt in place; the the four arms now have a little tension on them.
I hate to admit it, but I'm not really sure how it works, but it does.
Pics of my 31 here -> http://www.billzilla.org/newrcar.htm

[Greg Locock]

Dixon has a simple diagram of the linkage, and claims the rc is at the intersection of the two long links.

what else do you need?

[carlt]

Cheers guys , that was quick

Greg - re the Mumford , I have seen various pictures , diagrams/some with dimensions of the links ,
the trouble is the two most detailed diagrams show the pivot points of the bellcrank and rocker in different geometric positions .
I don't have computer skills to work this out , I would model it full size in wood to work out what I need , just thought it might be interesting and maybe save a lot of fabrication to ask you clever chaps first
I assume the Mumford is not as simple as it appears , I think it needs careful calculation to prevent the roll centre moving about when in use [ my math is as basic as my computer skills ]
Excuse my ignorance - who is the Dixon you refer to

Bill - I have been reading your site with great interest over the past weeks [ since coming across it while researching this subject ] It really is great stuff , very interesting life you have

I think the TAM works by using the torque reaction of the axle under acceleration , against the squat loading of the chassis , to create a traction enhancing load through the tyre contact patch ?
If my research/[spying] is correct ; viewed from the side with the car at ride height , the TAM links are : long bottom link , angled slightly up from the axle to chassis , shorter top link angled slightly down from axle to chassis ?.
As can be seen from my description , calculations are lacking !
I am basically an instinctive [ which results in lots of trial and error ] suspension modifier/builder.

With reference to your roll centre question - The Buckler will have a low front roll centre , low roll centres seem to work for me , I am doing this as a suspension engineering exercise for my own interest and I want what I consider the ultimate live axle location/set up

For my Buckler I am using what is a very basic [but full of lovely potential] chassis and adding/enhancing it with minimum tubing , but with 50 years of spaceframe advancement to work from .
The two options of axle links I have in mind for this car are :
1 - equal length links [20" governed by existing leaf spring mounts] , leading top link angled down slightly from chassis to axle , trailing bottom link angled up slightly from axle to chassis [both links adjustable for angle and length on axle mounting]
2 - unequal length links [20" bottom , 16-17" top, top link location and length not governed by existing chassis] bottom link angled up from axle to chassis , top link angled down from axle to chassis [as above , links adjustable on axle]

I would really like some more detailed info on the geometry / dimensions Mallock uses to make this system so effective

Bill - With reference to your Mallock 31 , do you still have the Mumford links you removed , any chance of some measurements ? maybe of the 4 link and their spacial geometry as well ?
please, pretty please

I will try and post a pic of the chassis [ taken last year by my brother , the other Buckler next to it is our 1953 MK5 Trials car]

[sorry , its defeated my IT skills , how can I post a photo thats attached to an email I received ]


Cheers
Carl

Edited by carlt, 25 July 2009 - 10:19.

[Bill S]

Bill - With reference to your Mallock 31 , do you still have the Mumford links you removed , any chance of some measurements ? maybe of the 4 link and their spacial geometry as well ?

We've removed the Mumford link as the car now has a an IRS & Hewland in the rear. I'll see if I can dig up the Mumford, from where ever it currently lurks ....

[cheapracer]

I assume the Mumford is not as simple as it appears , I think it needs careful calculation to prevent the roll centre moving about when in use [ my math is as basic as my computer skills ]
Excuse my ignorance - who is the Dixon you refer to



2 - unequal length links [20" bottom , 16-17" top, top link location and length not governed by existing chassis] bottom link angled up from axle to chassis , top link angled down from axle to chassis [as above , links adjustable on axle]

Firstly can I ask why you want to change from the rear leaf springs - if I bought a '56 anything it would be to experience a '56 car as it was in the day.

I have never used a Mumford but it appears that it keeps the RC very consistant, thats it's and a good feature. You can put the RC where ever you want with it as with most systems but especially low and below ground level if required (but not recommended unless you like dramatic moments of understeer).

I have done a number of 4 links and heres my thinking...

Make the lower links reasonably as long as practical, your 20" is about minimum, and not quite parallel to the ground at full compression (have the front of the car raised by 1" as a pitch allowance when you check that), that parts easy.

Now the top links are a bit harder to decide on - whats your driving style?
Do you like hard braking, tail stepping out type turn ins? Thats short links top links turning your axle under roll at high pitch angles. You need power though to keep the tail rotating, if low power and going uphill probably big time loser.

You can see where I'm going, medium length as in your number 2 example but parallel will probably come out best with slight roll/turn in rotation if you can make a smooth and early transition back on the gas.

If your a classic line smooth type driver then go for equal length.

No nonsense about this angle and that angle, keep them parallel initially to each other (again I mention they should not quite get to parallel with the ground at full compression) but make the top chassis pivot points adjustable so you can experiment by dropping the arm up or down - remember it arcs so you need a banana shaped mount or adjustable arms to suit.

You could also just use a couple of control links on top of your axle retaining your leafs, leafs aren't as bad as everyone makes out and actually have damping advantages as well as natural anti roll characteristics .

[Greg Locock]

Well, traditionally we use Meccano rather than wood, but that's the right general approach.

John Dixon, Tires Suspension and Handling.

Not worth buying for that half a page alone, if you already have Milliken*2.

[Bill S]

If your a classic line smooth type driver then go for equal length.

No nonsense about this angle and that angle, keep them parallel initially to each other (again I mention they should not quite get to parallel with the ground at full compression) but make the top chassis pivot points adjustable so you can experiment by dropping the arm up or down - remember it arcs so you need a banana shaped mount or adjustable arms to suit.

You could also just use a couple of control links on top of your axle retaining your leafs, leafs aren't as bad as everyone makes out and actually have damping advantages as well as natural anti roll characteristics .

Agree - It may not be quite as good as a trick TAM setup, but it does work very well.
Take a look at the bottom of one of my pages - http://www.billzilla.org/rcar2.html - you'll see that I have that setup on my current racer and it works nicely.

Edited by Pascal, 06 January 2011 - 11:52.

[carlt]

Agree - It may not be quite as good as a trick TAM setup, but it does work very well.
Take a look at the bottom of one of my pages - http://www.billzilla.org/rcar2.html - you'll see that I have that setup on my current racer and it works nicely.

I also agree

But ' been there , done that ' with my Lotus 7







We won the British class Championship 2 years running with this.
it had parallel trailing links and sliding pillar 'A' frame


I also have this Moggy , which I started hillclimbing with , it had top trailing links and lower 'A' frame - kept bending the axle tube ! - It is being modified to the same link system as the Lotus



I want to do something a bit more trick and interesting with the Buckler
Cheers
Carl

[cheapracer]

I want to do something a bit more trick and interesting with the Buckler
Cheers
Carl

Space frame torque tube.

[Ray Bell]

Originally posted by cheapracer
Space frame torque tube.

Ah yes... the thing I dream about...

My mental plan for a Clubman built under the old rules includes this, and using a Peugeot 403 rear axle, there were bolts aplenty to nicely mount it at the axle end. The full plan includes a couple of other more outlandish things to do with brakes, too.

There was a Clubman built here with a torque arm in the rear end, but for some reason the builder fitted a coil/damper unit on the chassis end of it!

Edited by Ray Bell, 26 July 2009 - 21:27.

[carlt]

Space frame torque tube.

I've got a couple of Trials Specials , one with a torque tube the other with 'A' frame with the base of the 'A' fixed to the axle
Great for traction , but the understeer , they tend to lift the front wheels completely off the ground !

[mariner]

A past copy of Racecar Enguineering had a full article on the Mumford link and "TAM". I wish I could tell you which one but all my RE's are stacked away as we re decorate the study!!

[carlt]

A past copy of Racecar Enguineering had a full article on the Mumford link and "TAM". I wish I could tell you which one but all my RE's are stacked away as we re decorate the study!!

do you want a hand with the decorating ?

[mariner]

Now we have to wait for the plasterer to do our study so I had time to find the Racecar Engineering article on the Mallock rear suspension.

It was actually in vol 3 , issue 4 in 1994 and was written by Arthur Mallock only a few weeks before his death.

The article was basically his justification of the use of a solid rear axle in most of his Clubmans cars ( 160bhp nad 400kg weight). Since the Mallock U2's got close to contemporary F3 times his argumants desrve listening to.

Basically he argues that the big advantage of a solid axle ( in a racecar) is that the wheels are ALWAYS upright in roll,acceleration and braking so the objective is to minimse the disavantages. His argument is that the standard objection of higher unsprung weight is less important once high downforce levels exist.

THe special trailing arm location mentioned above is to set the anti squat cancellation at 0% on one side and 70% on the other so as to cancel the diff. torque reaction. Arthur argues that by using shorter top than bottom trailing arm lengths you get a situtation analogous to the SLA impact on roll centre movement so the actual percentage anti squat can be held constant at any ride height thus improving stability. He argues this is a benefit of a solid axle as you can't easily do this on IRS layouts.

The purpose of the Mumford link is to set the rear RC very low to minimise sideways axle shift whilst packaging the linkages above the rear venturi. Because of the front engine design and use of a solid axle the Mallock U2's could run a large venturi so getting the linkages all above the RC was important. the Mumford link does this by creating a virtual RC below its parts. these consist of two cranks , one a bell crank which keeps movement from the pull rods in the same direction, and one a rocker which reverses the motion. Each crank is fitted to the chassis via a central hole. As roll to the left pushes the left link to the right its movement also pushes the right pull link to the right via the two cranks so there is freedom of movement, as there is when the links both rise in bump etc.

THe U2 was a very effective race car on most UK tracks and has always done well in hillclimbs where traction is critical.

On the only Clubmans car I ever designed I was not nearly as clever as Arthur but I got the rear RC fixed in relation to the chassis and CG simply by using a reversed lower A frame with the A arms fixed to the axle and the point fixed to the car on a bottom cross rail. this kept the RC at about 3.5" with a 3" ride height. It had one advantage that all the loads were fed into the chassis well ahead of the rear axle line so reducing weight compared to the U2 system but it was not nearly as adjustable for RC and Anti squat.

[Ray Bell]

You don't want to know how well the same philosophy with a front axle works...

Somewhere in TNF there's a thread about Welsors.

[wrighty]

There was a Clubman built here with a torque arm in the rear end, but for some reason the builder fitted a coil/damper unit on the chassis end of it!

without seeing a picture i may well be talking out of my rear end (posterior, not car rear end lol), but i believe the small coil/damper on the front end of an axle link helps to reduce the acceleration torque reaction by allowing the axle to rotate slightly, thus softening the break-away of the tyre under heavy accelerating load. I've seen it on stock cars (usually F2s where traction is at a real premium) and older sprint cars, where the lack of a clutch means that the power delivery is very on/off. The sprint car version was quite simple, effectively a rubber bush mounted on the link end instead of a rose joint, with a cup-type bracket on the chassis to retain the bush - the F2 type was more complex, with a small coil mounted on the link arm, with the securing cup on the chassis rail......both seem effective

[carlt]

Ray Bell - nice one [ i'll stick the link here to save some searching http://forums.autosp...w...&hl=welsors ]


mariner- that's great , thanks for taking the time to dig that out

Is it an in depth article from Mallock , worth buying a back copy [ if they have such ] ?

I would still love to know what the ratio/geometry of the 4 links and their relative chassis/axle pick ups are to create the TAM 5

Edited by carlt, 28 July 2009 - 21:29.

[gruntguru]

THe special trailing arm location mentioned above is to set the anti squat cancellation at 0% on one side and 70% on the other so as to cancel the diff. torque reaction.

Interesting to note the exact values required will depend on final drive ratio as this determines the ratio of axle torque to tailshaft torque.

The torque arm mentioned by Ray Bell is/was quite common in speedway dirt sedans. The arm is mounted to one side (RHS for CCW engines) of the tailshaft - again to eliminate L/R load transfer due to tailshaft torque and again, the ideal amount of offset will depend on final drive ratio.

Edited by gruntguru, 29 July 2009 - 00:35.

[Ray Bell]

Hmmm... and I thought it would be all so simple...

Then again, nothing ever is!

[Greg Locock]

Look at Billy Shope's website if you have a craving to learn more about torque reaction for live axles than I have.

http://home.earthlink.net/~whshope

[carlt]

Look at Billy Shope's website if you have a craving to learn more about torque reaction for live axles than I have.

http://home.earthlink.net/~whshope

Thanks Greg ,
that link has some really useful info for those of us [ well me at least ] with limited math capacity
- hopefully my logic fuse will hold out

[carlt]

Look at Billy Shope's website if you have a craving to learn more about torque reaction for live axles than I have.

http://home.earthlink.net/~whshope

Having had a read and a think on contents of the above link to Billy Shope's site , one question sprang to mind , which I'm hoping you clever chaps can answer :

On the first page , where he outlines the basic vectors involved with acceleration / launch , it's not until the bottom of the page , where he discusses IRS , that there is mention of 'a moment equal to the product of the tractive force and the tyre radius '

Does this moment not occur with a live axle ?

from my experience , and surely from basic physics it must be there , it is the equal and opposite force to the driveshaft / halfshaft torque ?

Cheers
Carl


[ hark at me - mathspeak , moments and vectors ,- I thought moments were what one had while driving those horrid vauxhalls ]

[gruntguru]

On the first page , where he outlines the basic vectors involved with acceleration / launch , it's not until the bottom of the page , where he discusses IRS , that there is mention of 'a moment equal to the product of the tractive force and the tyre radius '

Does this moment not occur with a live axle ?

from my experience , and surely from basic physics it must be there , it is the equal and opposite force to the driveshaft / halfshaft torque ?

Greg can probably enlarge but I think the live axle is treated as a force acting at the contact patch, since everything (including torque) is reacted through the suspension linkages. In the IRS case the "push" is applied at the axle height and acts through the suspension linkages and the torque is reacted at the mounting of the diff or transaxle.

[Greg Locock]

In an IRS the spindle, and hence the suspension, doesn't 'see' the halfshaft torque, the halfshaft pushes forward on the wheel bearing and that is that.

In a live axle there are three traction related forces, torque in, and the two contact patch forces. In side view only the latter two matter, so there is a torque thrust*rr about the wheel centre.


That sounds like the opposite to Billy's page, it isn't it is exactly the same. His diagrams show why, he is treating the suspension+engine as a solid body for the live axle and is then modifying that for the IRS.

[Spaceframe7]

Hello Carl,

Many years ago I was in contact with Arthur Mallock who was extremely helpful with some questions I had on solid rear axles (disc brake conversions, axle strengthening, location etc.). Mr. Mallock really went out of his way with 3 lots of correspondence to me (all typed by him I believe - before computers were fully utilised by his company), and he sent me some diagrams on TAM and Mumford set-ups. Some of it may have been reprinted in Cars and Car Conversions as they did a number of articles on Mallocks (involving Father and Sons) which I also have, and if you would like copies, I can scan them for you and send them gratis to your e-mail address. Being new to this site, not sure how we can securely exchange e-mail addresses, but if you know of a way, please advise.

Edited by Spaceframe7, 10 September 2009 - 18:49.

[Bill S]

Hello Carl,

Many years ago I was in contact with Arthur Mallock who was extremely helpful with some questions I had on solid rear axles (disc brake conversions, axle strengthening, location etc.). Mr. Mallock really went out of his way with 3 lots of correspondence to me (all typed by him I believe - before computers were fully utilised by his company), and he sent me some diagrams on TAM and Mumford set-ups. Some of it may have been reprinted in Cars and Car Conversions as they did a number of articles on Mallocks (involving Father and Sons) which I also have, and if you would like copies, I can scan them for you and send them gratis to your e-mail address. Being new to this site, not sure how we can securely exchange e-mail addresses, but if you know of a way, please advise.

*sticks hand up*
I'd love a copy as well thanks mate.
I'll send you a private message (look up the top-right of the page) with my email address.

[carlt]

Hello Carl,

Many years ago I was in contact with Arthur Mallock who was extremely helpful with some questions I had on solid rear axles (disc brake conversions, axle strengthening, location etc.). Mr. Mallock really went out of his way with 3 lots of correspondence to me (all typed by him I believe - before computers were fully utilised by his company), and he sent me some diagrams on TAM and Mumford set-ups. Some of it may have been reprinted in Cars and Car Conversions as they did a number of articles on Mallocks (involving Father and Sons) which I also have, and if you would like copies, I can scan them for you and send them gratis to your e-mail address. Being new to this site, not sure how we can securely exchange e-mail addresses, but if you know of a way, please advise.

That is a very kind offer , thank you
I will send you a Private Message [ PM ] with my Email address , the PM is pretty secure and obviously is private , so isn't displayed for general viewing
Looking forward to the scans
Regards
Carl
ps as Bill said - look at top r/h of page , click on Messages

Edited by carlt, 11 September 2009 - 08:02.

[maverick69]

Hi Guys

Is there any chance that I can get my hands on that information about TAM? I'd really like to figure out how the system worked and there is a distinct lack of material on it!

Many thanks.

Edited by HarryReams, 05 November 2009 - 15:01.

[Spaceframe7]

From Harry Reams - Quote: Is there any chance that I can get my hands on that information about TAM? I'd really like to figure out how the system worked and there is a distinct lack of material on it!

Hello Harry,
Will await you e-mail address and can then forward pertinent information to you.
Regards and Happy Motoring.
SS

Edited by Spaceframe7, 22 December 2009 - 03:38.

[Billzilla]

I believe one member never did receive the information as his computer kept rejecting the files I tried to send him from my IMac (not caused by a virus from either of us I hasten to add!). If he still wants it (cannot recall his e-mail address), I will send the info to any that are still interested. Regards, all the best for the Christmas season, and Happy Motoring. SS

I'm pretty sure that was me, and yes I received them thanks. The problem was that I deliberately have a small email box so people can't send me huge files (usually .bmp photos of something I already know about) that take ages to download. I'm also pretty sure I replied with a thanks ... ?

[Spaceframe7]

I'm pretty sure that was me, and yes I received them thanks. The problem was that I deliberately have a small email box so people can't send me huge files (usually .bmp photos of something I already know about) that take ages to download. I'm also pretty sure I replied with a thanks ... ?

Hi Billzilla,
Hello again. It was actually another member who couldn't receive the info., (three out of four of you received the articles o.k.), and he has contacted me this date. Glad you received the information, and yes, you did thank me. Have a great holiday season.
Regards,
SS

Edited by Spaceframe7, 15 December 2009 - 18:55.

[Spaceframe7]

Look at Billy Shope's website if you have a craving to learn more about torque reaction for live axles than I have.

http://home.earthlink.net/~whshope

Hi Greg,
Received your message and will send off the information in the early New Year if this is o.k.? Apologies, but please send your e-mail address again, as for some reason, I couldn't get it from this bulletin board.
Regards,
SS.

Edited by Spaceframe7, 15 December 2009 - 18:55.

[Spaceframe7]

To Billzilla

Is it permissible to inquire who banned you?

SS

Edited by Spaceframe7, 22 December 2009 - 03:41.

[Greg Locock]

S7- thanks, got the entire archive. Had a bit of a think about it. Kinematically it is very similar to an inverted Watts link, that is as used in the Australian V8s (I think), where the centre is mounted to the body, and the long links terminate at the axle.

This fixes the roll centre with respect to the BODY, that is, the opposite of a normal Watts, which fixes the RCH with respect to the ground. So, the Mumford has what I would call a RCH gain (in bump) of -1. A typical IRS would have an RCH gain of say -.5 to -.7, and a conventional Watts is 0.

I haven't any great thoughts about what that means precisely, I do remember being warned off setting up an IRS with RCH gain of 0, but cannot remember by who or why.

The advantage compared with an inverse watts link is that the RC is below the linkage, as described in my first post, whereas the Watts in its conventional form always has stuff hanging out below. There is a further rejig of Watts that gets around it but that has its own problems.

Now of course the great question is why a super low RCH is such a great thing, but there again, the cars it is used in are so different to what I work on that I'd believe anything that sounds reasonable. I'm 'meh' on the gain for a racecar, if the suspension doesn't move much vertically then it doesn't really matter what the gain is.

Just for grins here's a bolt on conversion kit that turns a Panhard rod car into a reverse watts. Well I guess if that's what you want to do this is the way to do it. Should sort out your weight distribution problem as well http://www.stranopar...30606170905.jpg

and this pissing match is quite funny - at least one of these guys is talking through his hat. http://www.thirdgen....-new-watts.html

Edited by Greg Locock, 26 December 2009 - 22:40.

[SteveCanyon]

S7- thanks, got the entire archive. Had a bit of a think about it. Kinematically it is very similar to an inverted Watts link, that is as used in the Australian V8s (I think), where the centre is mounted to the body, and the long links terminate at the axle.

This fixes the roll centre with respect to the BODY, that is, the opposite of a normal Watts, which fixes the RCH with respect to the ground. So, the Mumford has what I would call a RCH gain (in bump) of -1. A typical IRS would have an RCH gain of say -.5 to -.7, and a conventional Watts is 0.

I haven't any great thoughts about what that means precisely, I do remember being warned off setting up an IRS with RCH gain of 0, but cannot remember by who or why.

The advantage compared with an inverse watts link is that the RC is below the linkage, as described in my first post, whereas the Watts in its conventional form always has stuff hanging out below. There is a further rejig of Watts that gets around it but that has its own problems.

Now of course the great question is why a super low RCH is such a great thing, but there again, the cars it is used in are so different to what I work on that I'd believe anything that sounds reasonable. I'm 'meh' on the gain for a racecar, if the suspension doesn't move much vertically then it doesn't really matter what the gain is.

Just for grins here's a bolt on conversion kit that turns a Panhard rod car into a reverse watts. Well I guess if that's what you want to do this is the way to do it. Should sort out your weight distribution problem as well http://www.stranopar...30606170905.jpg

and this pissing match is quite funny - at least one of these guys is talking through his hat. http://www.thirdgen....-new-watts.html

The Mumford Link wasn't so much invented to make a really low roll centre, but to allow the later front-engines Mallock's to have a clean rear undertray that had no suspension bits hanging out of it to disrupt the airflow. The roll centre with the Mumford doesn't have to be all that low, it just allows it very easily. On the Mk31 I have the front & rear roll centres are pretty close in height to each other and move up/down at about the same rate with wheel travel, I think. (Though now the car has an IRS so no Mumford)

On my 'old' racing car we have a conventional Watts Link, however it sits horizontally.



That's an old photo taken during its rebuild. The entire link unfortunately sits under the rear bodywork but the car is certainly no aerodynamic masterpiece so I just drive it an not worry about it at all.

Billzilla.