Looking at the MGB Front Crossmember, Damage Assessment, Weight Reduction & Steering Modification
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- Опубликовано: 10 сен 2024
- Looking at the MGB Front Crossmember, Damage Assessment, Weight Reduction & Steering Rack Modification
A quick video looking at the front crossmember of my MGB after the accident at Snetterton in 2022. I am trying to assess which holes are useful to provide a crush zone in the event of another accident and prevent damage to the chassis leg. Another benefit is the weight reduction that the holes give. Finally, I think some pillow blocks might be useful the raise the steering rack slightly.
I'm no expert when it comes to engineering and crush zones and would be very keen to hear people's opinions on whether to add the holes and where they should be.
Removing material from the crossmember will affect its structural integrity both in the loads that it will be able to handle (and corresponding deformation under load) as well as its harmonic natural frequencies. One way to determine this would be to do some finite element modeling of the crossmember (ie mathematical discretization of the structure with force loading as well as a modal analysis to determine its natural frequencies which are done via computer simulations). You could run these for the existing stock cross member and compare to results from models with an increasing number of holes. My guess is that the stock crossmember is way overdesigned and could be put on a diet. With that said, there is no substitution for actual testing. You could buy a few additional cross members and modify them to a varying degree then install them and actually try them out on a track to see the impact on performance and handling. What a great little research project that would be!
Many thanks Steven, I fully agree that applying modern technology would be a great way to see what is really possible with older engineering. It would be fantastic to see how much one of these cars could be developed with modern techniques.
Hi David, Cosidering that the crossmember takes all the forces generated by the front suspension plus the torque from that substantial anti- roll bar I would leave it as it is.
This is indeed one very well designed unit, don't compromise it's integrity.
All the best for your upcoming season.
Many thanks for your message Roger, as far as I could tell the original drilled crossmember held up well; it lasted 7 years until the accident at Snetterton. What I'd really like to know is whether having holes in the part will do anything to save the front chassis legs. I think having the holes around the mounting areas was certainly not beneficial, but I do wonder if some holes in the right places might be enough to take the impact away from the body in the event of an impact.
@@davidrussellwilks Hi David, I think your assessment of taking half a Kg out of the crossmember seams sensible, I don't think your going to save the main chassis legs by taking any more weight out. You were unfortunate to hit such a unyielding structure, maybe a few more straw bales are needed!
David, I noticed that you asked on a forum which oil to use for the gearbox... normally people use the 20W40 Castrol engine oil. However I use for the track gearbox oil GL-4 and that is ok for the yellow metals. I have a video soon on it
Many thanks for your message, I had been using the GL-4 from Driven (after a few recommendations). Last year I had both gearboxes rebuilt by Mg Motorsport and was recommended to use the Castrol Classic XL30, so far this seems to have worked very well, I would like to try and get a full season with the same gearbox to know for sure though.
Love your channel, good work at Goodwood threading the needle, and a good finish at the end.
Thanks Lance, I was glad to finish the race unscathed!
Great to see you back David happy new year hope you do well this year looking forward to seeing you putting in the new engine at the end of the month 👍🏻
Many thanks Anthony, I may not video the entire engine installation but will certainly add some content once it's ready. I finishing painting it back in September and was very pleased with the results.
You could probably dimple the holes so it would have more structural integrity too
Hi David, I am not a racer, only an MG enthusiast. Personally, I'd just leave it as is. It is low slung weight so I don't see the benefit of removing one kilogram. The weight savings is about the equivalent of less then a half of a gallon of fuel.
Thanks for your message David, ideally I'd like the crossmember to act as a kind of crumple zone for the body, it's far easier to change this part rather than the chassis leg. The problem is knowing whether having holes is any benefit at all to protecting the body.
@@davidrussellwilks Could you fret out the whole area across the sub-frame where you have several holes drilledand weld in an x of quarter inch rod to brace that area?
Hello David. Happy New Year to you too. I subscribed not long ago as I would love to get into racing with an MG B myself. It won't be happening anytime soon though as I have lots of other projects to work on right now. Anyway, this topic is interesting. It is difficult to judge where it would be safe to remove material and where best to leave it. I tend to think about this by imagining the part and the strain it goes through while it is being used. Where would it flex upon hard cornering? What would happen in case of an impact (you seem to have learned a valuable amount of experience there, glad you came out unscathed!), and lastly would it really be worth sacrificing structural rigidity over a kilo or so? I personally would like to test something a little different, as in cutting out material as you did previously, then weld a bead on the rim of the cut to temper the steel afterwards. I wonder if it would allow for some strength to remain after having removed the metal... Just speaking my mind here. All in all, I would look for a durable result. I understand that back in the day they did all they could to win races, knowing that durability is being sacrificed in the long run. I would much prefer casually racing for many years rather than being in it to win it, as it were. Kind of defeats the purpose of racing, certainly, but it must be so much fun I would just want it to last. :-) Many thanks for sharing your racing with the world. It is precious. Let me know if you will be racing at Spa Francorchamps anytime, as I live in Belgium and go to the track quite often. Take care, and happy racing!
Many thanks for your kind message Geoffrey, the main thing I am keen for the crossmember to do is to form a sort of "crumple zone" in order to protect the chassis rail in the event of an impact. To me the front crossmember is very easily replaced and far cheaper than any repair to the chassis rail would be. I guess the only real way to know is to repeat the incident from Snetterton with an unchanged crossmember and see the difference!
I don't think I'm at Spa this year, but will be at Zandvoort in July.
@@davidrussellwilks Crumple zones make perfect sense. They are designed to absorb the energy of an impact to protect the occupants, in modern day vehicles. Since the cross-member joins both front chassis rails, wouldn't the crumpling of said part make the chassis rails more prone to movement, in case of an impact? It all depends on the nature of the impact I suppose (which I hope will never happen again to you)... Anyhow, I am looking forward to how this rebuild turns out. I really appreciate your effort in making this content, it is highly interesting.
I missed a '67 B GT restoration project a couple of weeks ago, still keeping an eye out though. :-) Take care, and maybe see you in Zandvoort.
You've hit the nail on the head there Geoffrey, I was thinking about it more last night, I want the strength around the chassis leg to be as good as it can be, so really the only place for any crumple zone needs to be around the shock absorber/ spring mounts and possibly underneath the crossmember. Another idea popped into my head last night and this was to flare or swage any holes made to give very good strength and also some weight reduction. I'll certainly wait a week or so before cutting anything out!
@@davidrussellwilks Flaring will definitely give some added rigidity. Given the thickness of the sheet metal on that subframe it will require good quality dies and a decent hydraulic press... And as the saying goes: measure twice, cut once. Haha. Are these subframes being re-manufactured, by the way? You mentioned how easy it is to source a new item.
Happy new year to you David. I'm not overly convinced about weakening the crossmember too much it may cause the chassis rails to deform in a hard impact and would you really notice any difference with a few hundred grams missing, half a litre of petrol? As for moving the rack upward, won't this cause all sorts of problems with the lower column matching at the UJ by the bulkhead, it has to be at the correct angle I believe or it will become notchey as you turn the wheel. Good luck with whatever you decide to do and I hope your season goes well,
Thanks for your message Tim, in an ideal world I'd be able to figure out what is any holes are required to give the chassis rail the best chance of surviving the impact. It certainly seems that the middle section and the area where the crossmember bolts up should be as strong as possible.
With regards to the pillow blocks, they would be removable, but I don't know exactly what the effect would be. I would like to try to find a way to add a bit more clearance between the front pulley and the steering rack, they run too close together for my liking.
Cheers for the video David! I am currently in the process of rebuilding the Front Axle on my 79 MGB GT with Superpro Polybushes, Extended Lower Arms, Etc & ill be really interested in what you do with your cross member, from my rather limited knowledge, im sure if you cut out & then ad a press to fold the edges of the whole round should give you a massive amount of strength incase of another accident. Hope the helps & please let us know what you decide to do with the cross member.
I'm sorry but i missed your message. I have made a trial run with a press tool on the damaged cross memebr and it cut is fairly easily. I am hoping that if the holes can be flared very little strength will be lost. A problem I do have though is that the punch tool will not fit into the middle part of the crossmember so I will need a find another way of flaring those holes. Hope all goes well with your work, I've been really impressed with the SuperPro bushes and would recommend them to anyone.
Another vote for not drilling any holes - for just a kilo saving, it's hardly worth it. Let's face it, a good breakfast can add that much!
Hi David, I've just started a B project to hopefully race in Equipe as well. The swaging of the holes like Geoffrey mentioned is something I'm thinking of doing too. My only thought was that getting the tooling inside the axle would be tricky in places potentially? Look forward to seeing how you get on, I'll be using your car for inspiration!
Many thanks for your message Tom, looking at the crossmember this evening I don't think it would be a problem to fit the swaging tool/ dimple die into it as both ends are open. However the thickness of the steel may make it difficult for the tool to work; at 3mm it seems the metal is too thick for the ones I was looking at this morning.
Just going back to your previous comment, I bought a hydraulic press tool and the head part is just too big to fit inside the crossmember, I'll be adding a video on it soon.
a 1KG savings, hmmm I would lose some weight as a driver, instead of cutting holes in the subframe... those holes are IMO causing even more damage to the chassis arms...
Too true with regards to a bit of weight loss for the driver! I may add some small holes in places, I was really hoping to be able to flare the holes but unfortunately I can't fit the tool in to do so.
David, How about welding up a new crossmember out of 1 x 2 or so.
I think for our series regs the suspension pick up points have to be the same as original so I would be unable to fabricate on myself. I should also check to see what's permitted in terms of holes!
A kilo here or there, while of critical importance, is distracting and is less important than developing the driving skills to achieve faster laps times.
Hi ,what is the engine spec of the engine ?
Thanks for your message Daren, there's a page here with most of the specs, www.britishracecar.com/DavidRussellWilks-MG-MGB.htm. More recently class rules have meant the capacity is 1850 rather than 1950cc
Hi David,
I have just purchased the Al Pease MGB. Fascinating history! Yes a few less burgers in the new year for me also!
Excellent news Tony, a true piece of MGB and Automotive history there. Are you planning to race the car in 2023?
@@davidrussellwilks Yes that is the plan. It has been sitting for a few years so there will be a fair bit to do. It is currently in Saskatchewan and I am in Ontatio.
I may fit the spare Derrington cross flow Weber setup to my current race MGB in the short term. That is how Al ran the car before he supercharged it. I will leave the supercharged setup on the Al Pease cat until I have run it on track. See how it works.
@@davidrussellwilks who do you use for head work for your race MGB? Keep the videos coming. They are a great tonic for the off season. I have raced in the UK recently but in HSCC vintage formula ford.
Excellent news regarding the car Tony, really great to see that you'll have the car back on track. For the most recent cylinder head I used Peter Burgess; he is very well regarded in the UK.