MR4BC Special - Broken front shock tower mount

[AndyP]

Hi,

Just joined the forum, Hi to everyone, and also new to Offroad racing.

Got an MR4 BC Special 2 weeks ago, racing today at Leighton Buzzard and broke the front shock tower mountings, which I understand is common on the BC. Not surprising I guess given that there's only 2 x 15mm M3 nuts holding it to the front bulkhead cap. I *think* this happened after landing from a jump.

So, my question is - What can I do to prevent this happening again ? I guess I'm thinking along the lines of some kind of strengthening, but what to add and where ?

Has anyone else experienced this, and if so how did you fix the problem ?

Thanks

Andy

[Doomanic]

Did you put the two small self tapping screws in through the shock tower into the bulkhead cap?
If so, there's not a lot else you can do, except not crash! ;D

[AndyP]

OK, just had a look at the shock tower, now I see the small holes you're talking about - No, I didn't put the screws in, and I can't find anything in the instructions about it either. Does explain why 2 small screws were left over after assembly.

I'll fit them when I get the new bulkhead cap, but I'm going to put some further bracing in too, just to be extra secure. Just need to be careful I don't transfer the load to the next weakest link....

Thanks


Andy

[mike.stening]

one suggestion which has been taken up by a few racers in america, and that is to fit the carbon mounts from the MX4, you'll need the MX4 gearbox cover, and the shock mounting and camber mount, this is much stronger, you can eithe go for the one from yokomo or check out the ones on the fibre-lyte web site which have extra monting positions for both shocks and inboard camber. you shouldnt break these. i havent ;D

[Doomanic]

Good idea Mike, except for one small problem.......
CML do not have the parts in stock to complete this conversion. >:(

[sosidge]

CML do not have the parts in stock to complete this conversion.


:'(

[mike.stening]

WHAT!

ah that sux
hmm, i dont think i have any spares for that bit either.

well that is your best bet, getting the bits from fibre lyte shouldnt be a problem but you will need the parts from cml so you may have to put up with the standard weaker stuff >:( :-[

[AndyP]

Thanks to all those that have posted in response to my initial post, I've now obtained a replacement part, but I'm going to make an aluminium brace to hopefully add a little more strength to the front shock tower.

Since I'm using 1.2mm Alu, it should have a little 'give' and hopefully won't transfer too much force to other parts.

I'll post pictures/info when I've completed it.

If that doesn't prove strong enough then maybe I'll have to try and source the MX4 parts instead....

Thanks

Andy

[mike.stening]

sosidge made some modifiactions to his front shock mount a while back, it may be worth you checking his web site for info on this to save you the hassle
www.sosidge.pwp.blueyonder.co.uk
plenty of info tthere

hope that is allowed

[Doomanic]

I was going to get some carbon fibre shock tower braces made up, but after discussing with a couple of BC drivers I decided against it. If you strengthen the tower, you move the force to the next week point, in this case the front bulkhead cap.
Since this still seems to be a problem, if I can get firm orders from at least 5 people, I will get some made. Unsure of the price at this time, but likely to be under a tenner.

[sosidge]

I've not had any problems with my homemade brace since making it, but by the same token I can't recall any big rolling impacts either - I've taken a fair few high jumps with bottom-out landings though. I've seen just as many people break the bukhead cap as break the tower, but most who break the bulkhead cap have overlooked the little screws.

[AndyP]

All,

Been racing this weekend, and no breakage, so my new brace appears to be working, either that or I've been luck ( more likely... )

I did have plenty of rolls, and a few direct hits into a marshall (!!) and it didn't break so....

I'll post some pics tomorrow when I've downloaded them from the camera. Managed to make a small aluminium brace which goes from the front shick tower mounting screws which go into the bulkhead cap, down to screws which hold the top the of small bumber into the bulkhead.

Made one which didn't quite work, so that ended up being a rear brace, which has actually turned out OK.


Andy

[Eddie]

Did exactly the same on Sunday :( and even considered buying a couple last week as a few of the members at our club have broken there front mounts - DOH!

One lad even broke the rear mount which I've never seen before.

I'd be interested in anything that will make the front end stronger.

Doesn't the MR4 rally have the same mountings as an MX4? if you look at Pics of the rally the front shock mount looks like an MX4 to me. Never seen one in the flesh tho.

[sosidge]

The MR4 Rally does do things in a slightly different way to the MX-4, although they appear superficially similar.

It has a plastic mount, which attaches to the front of the bulkhead cap, and two plates (shock tower and camber link plate) attach to it, whereas the MX-4 tower fits straight on to the bulkhead cap, and the camber link plate is attached to the tower with aluminium spacers.

The Rally bulkhead cap comes as part of ZS-300F (front bulkhead, NOT for tourer), and the plastic mount comes in ZS-019 (Shock Tower Spacer - I have one in my spares box!).

You MAY be able to modify the MX-4 plate parts to fit the rally plastic parts, can't say myself as I don't have both in my hand. Or you could make some different plate parts to fit on the Rally plastic parts.

Anyone fancy trying? Perhaps a Rally owner and an MX-4 owner and a BC owner can join forces!

[mike.stening]

on the YMP site there is a front shocktower camber link mount that looks evry much like the MX4 version, not sure how it differs, it might just be a kit for the BC to convert it to the stronger MX4 type.
I know of a certain someone who is trying to get hold of the MX4 stuff including the bulkhead cap (which is the problem part i think)
shame the YMP stuff aint more widely avaliable.

[AndyP]

You can see the pictures of the braces I've made at http://www.cubecomputing.com/rc/mr4bcbrace.html

I don't claim that they're brilliantly constructed, and no doubt I will improve them, but you get the picture.

Andy

[mike.stening]

i'd like to see you try and break them ;D

do they add alot of weight?

[AndyP]

Mike,

They're 1.2mm Aluminium, very light weight.

On Sunday I was racing at the Mid-South regionals, and as such we were being weighed before competing. If I remember correctly I was within 2g of the allowed weight, hope that answers your question ! :)

Andy

[mike.stening]

nice, i only asked cos they looked heavy from the pics, looks can be deciving though ;D and looks arent everything :P ::)

[sosidge]

Neat idea, I reckon it will definitely stop the tower getting pulled from the bulkhead. I broke mine at the top though.

[mike.stening]

yeah but sosidge, yours was the original BC, the special has a slightly different material to make the towers a bit stronger, seems they may need to make the cap out of the same stuff too ::)

the only advantage i can see from the BC design over the MX4 is the aero dynamics which at these speeds probably wont make much difference, i suppose it would be lighter too.

las time i weighed my car i got 1.6 though i couldnt be more accurate than that.

[AndyP]

Just weighed my car, just using the digital scales in the kitchen, which gave a reading of 1579 grams, a little under the 1588g for BRCA 4wd events. this is fully race ready condition, excluding transponder of course.

Next time I take the braces off I'll weigh them and post the values. Don't think they'll be very much though...

Andy

[mike.stening]

hmm i find it a little odd then that my car weighs more. especially as the chassis i am using should in theory be lighter(TC special) and i wouldnt have thought the MX4 front shock tower mounts weight that much or the body and undertray.
maybe my scales arent that precise.

[sosidge]

I think I last weighed my BC at around 1650grams.

[mike.stening]

does the weight really make that much difference in the end?

[sosidge]

Well, yes, extra weight basically slows your car down all the way around the track, especially under acceleration.

[mike.stening]

well, yeah i kinda knew that :P
but what i ment was would 20g for instance make that much difference?, my car does feel quick but i was wondering if it is worth working on getting the weight down to the limit?

[sosidge]

Well 20 grams on a 1600 gram car won't make much of a difference, it's only just over 1%.

[mike.stening]

cheers mate, new i could rely on you for answers.

[sosidge]

My pleasure!

[ODB]

Come on boys, get your set up's in to CML so I can see what your all doin!!!
Anyone found any new radical set up's???

[Dave G]

dave you really that desperate for setups :P

dave

[mike.stening]

why does everyone seem to have such a problem with the BC? ok so there are less people working on getting them running right so it will take longer.
there are so many running the XXX4 that obviously a good setup will be reached earlier.
stick a load of monkies in a room with a type writer and eventually they'll write the works of shakespeare

[Dave G]

i was running a bc way before anyone else,practically the day they came out,poor parts availability was a problem.

dave

[ODB]

Yeh Dave I'm always on the look out for new ideas!!! ;)

Mike, not really sure about your comment.
I ain't got a problem with the BC....
I race up in the north east and national level where if we are lucky three or four BC's maybe racin, there could be up to 20 or so Losi cars at that event.They then usally have a set up sorted for that track after practise, unlike Danny and I who seem to get it somewhere near a good set up for the finals!
Why don't you come along to the Nationals and have a go?
People do smile at Nationals and they are fun.....


Just attempting to spread the good word about the BC.....

[mike.stening]

i i had the time i would do the nationals, maybe next year (once the baby is a bit older)
the monkies comment was that given enough time and imput a good result is always possible, working as a large team so to speak. ;D

[yokoracer]

i had the same problem on my mr4
the solution was got a strip of alloy and shaped it to fit instead of the shock tower at least it twists but not brake so i always menage to finish the race if you want give me your e mail adress and i send u a pic of what i am talking about my e mail is jmatx@maltanet.net since i done it i never retired due to shock tower let me know the cost for it was around 6 sterling and 1 hour work !!!!!!!!!!!!!!!

[yokoracer]

mistake e mail jmarx@maltanet.net

[BC Rog]

I'm not sure about this broken shock tower thing as I've only broken 1 in about a year with the car!!!

That was due to a car coming out of control (on it's roof) down the main straight at an indoor meeting (ie nowhere to go even if I had of seen him crashing!!). Did a rear tower in the same accident .... and just avout everything else too >:(

To be fair, once I stopped forcing breakages by being "creative" with my freeing up of the drive train :-[ In 1 season of nationals and regionals I have broken one front whishbone (my fault) and one rear hub carrier ... somebody hit me hard after I'd lapped them .... >:(

The car is very, very reliable .....

Rog