Bell crank suspension rockers
Discussion
I know this is not a normal feature of an Ultima, however i also know that there are a few people on the forum that have some experience with them, so If you don’t mind id just like to pick your brains for a bit. What I’m trying to work out at the moment is what size and style of bearing to use in them. So if you have any recommendations or experiences with them i would appreciate any responses. I seem to be getting varying responses as to what has worked verses what should theoretically work. I’m finding that people have been able to use stuff successfully that is under rated in the radial load capacity so i might be missing something when i’m working out what the loads are.
(if you can also list the rate of the spring used as well that would help)
Regards Ryan
It is not clear from your model how this will be fixed to the chassis so is therefore difficult to gauge what loads will apply.
It appears you are just going to transfer the spring/damper motion through the crank with a pushrod which I would have thought would just add weight and complexity. Should you not be considering a design change to the upper wishbone turning it into a rocker with the spring/damper inboard. In this way the rocker bearings can remain very similar to the current design.
Steve
It appears you are just going to transfer the spring/damper motion through the crank with a pushrod which I would have thought would just add weight and complexity. Should you not be considering a design change to the upper wishbone turning it into a rocker with the spring/damper inboard. In this way the rocker bearings can remain very similar to the current design.
Steve
Steve, It’s for the “Social climber” project that I’m working on with a few mates. We intended to fix it into the chassis like in the model below.
Id like to be able to take credit for it, but this is all Tim’s work. I just do the simple detail stuff on the bearings and he puts it all together.
These arrived in the post tonight, don’t know if ill use them, they don’t feel that nice, will have to try and clean them up and then turn up a pivot shaft for it.
Ryan
Id like to be able to take credit for it, but this is all Tim’s work. I just do the simple detail stuff on the bearings and he puts it all together.
These arrived in the post tonight, don’t know if ill use them, they don’t feel that nice, will have to try and clean them up and then turn up a pivot shaft for it.
Ryan
I got a reply from someone by PM, and tried to write back but i think it got blocked by a spam filter, So just so you know, thanks for the info and taking the time to respond. I have looked at the combined units from Pegasus. i think they may be overkill for this project. all up weight is intended to be less than 300 Kg (less than 660pounds) and i dont think it will go much over 200Km/h on most of the tracks we have access to so downforce will not be realy high.
if i bottom out a shock with a 400lbs/inch spring on it, and its got 3" travel it would be around 1200lbs force required to do so, so the resultant force in the bearing must be similar.
Has anyone got an info on bearing loads verses speed (number of RPM). I have a feeling that at very low rpm there may be an increas in the load capacity, just going on what ive seen.
Thanks to all, once again.
Ryan
if i bottom out a shock with a 400lbs/inch spring on it, and its got 3" travel it would be around 1200lbs force required to do so, so the resultant force in the bearing must be similar.
Has anyone got an info on bearing loads verses speed (number of RPM). I have a feeling that at very low rpm there may be an increas in the load capacity, just going on what ive seen.
Thanks to all, once again.
Ryan
ezakimak said:
I got a reply from someone by PM, and tried to write back but i think it got blocked by a spam filter, So just so you know, thanks for the info and taking the time to respond. I have looked at the combined units from Pegasus. i think they may be overkill for this project. all up weight is intended to be less than 300 Kg (less than 660pounds) and i dont think it will go much over 200Km/h on most of the tracks we have access to so downforce will not be realy high.
if i bottom out a shock with a 400lbs/inch spring on it, and its got 3" travel it would be around 1200lbs force required to do so, so the resultant force in the bearing must be similar.
Has anyone got an info on bearing loads verses speed (number of RPM). I have a feeling that at very low rpm there may be an increas in the load capacity, just going on what ive seen.
Thanks to all, once again.
Ryan
If a suspension truly bottoms out then the loads are a lot more than just multiplying the travel by the spring rate. A typical assumed value for a maximum vertical suspension loading on a road car is 6 times the static corner weight.if i bottom out a shock with a 400lbs/inch spring on it, and its got 3" travel it would be around 1200lbs force required to do so, so the resultant force in the bearing must be similar.
Has anyone got an info on bearing loads verses speed (number of RPM). I have a feeling that at very low rpm there may be an increas in the load capacity, just going on what ive seen.
Thanks to all, once again.
Ryan
If you are using a rocking link then the load on the centre bearing is the vector sum of the suspension load and the spring load. Adding them together is safe if trigonometry isn't your thing.
Bearings do not change in capacity at low speeds.
I am aware what happens when the shock bottoms out. I am not designing for 6G’s as i think that will be too heavy for a race only car. Thinking factor of safety around 1.2, 3G loading max, designed to bend not snap where possible. I doubt you would be still on the track with the foot into it if you had 20Hz 3G load into the suspension aero included.
I have found that McMasterCarr has been a good source for these bearings online, as they even have the CAD models available. Haven’t ordered anything from them yet so remains to be seen if they actually have what they say. I priced the parts for one corner of the car through them at ~$50Au, another one of the guys went down to the local bearing supplies and came back with a quote of $190Au.
This was the shopping list.
http://dl.dropbox.com/u/3913082/Documents/Proposed...
The ones that i got in the photo were as a lot from ebay, and i got them just as a sample so that I could get a good look at them.
I don’t think i would use them for wishbone suspension pivots on a tubular welded structure as it would be hard to get it all aligned. As a single pivot on a rocker its probably ok as there is less chance of misalignment.
This is starting to get off track and i think i may have posted it in the wrong area. Apologies to the Ultima Forum.
Where would one post on PH about building single seat racing specials. Designing and building from scratch ect.
I have found that McMasterCarr has been a good source for these bearings online, as they even have the CAD models available. Haven’t ordered anything from them yet so remains to be seen if they actually have what they say. I priced the parts for one corner of the car through them at ~$50Au, another one of the guys went down to the local bearing supplies and came back with a quote of $190Au.
This was the shopping list.
http://dl.dropbox.com/u/3913082/Documents/Proposed...
The ones that i got in the photo were as a lot from ebay, and i got them just as a sample so that I could get a good look at them.
I don’t think i would use them for wishbone suspension pivots on a tubular welded structure as it would be hard to get it all aligned. As a single pivot on a rocker its probably ok as there is less chance of misalignment.
This is starting to get off track and i think i may have posted it in the wrong area. Apologies to the Ultima Forum.
Where would one post on PH about building single seat racing specials. Designing and building from scratch ect.
Andy, Mini parts are harder to find down under than rocking horse droppings. Are you using these in the GTT?
I can jump online and order standard bearings easily and cheaply.
Was thinking of something like McMasterCarr part number 5972K82
ID12mm, OD28mm and Width 8mm single row sealed ball bearing as it’s easy to get, $5 Australian each at the local industrial supplies (a bit like an alternator bearing). They are also sealed and light, and would be easy to make an assembly to fit them. Keep in mind that this is going into an entry level small hill climb car, so something that results in $5000 per corner (once you include shipping) of the car in suspension bits and different bearings is going to break the budget.
The initial question related to what or how do you size these things?
what have other people used?
If you know the spring rate of the spring that would also be a good indication of the load as well i guess?
I think i’m getting closer to working out what would be an acceptable solution.
If I was doing it for the Ultima I would probably go with something like this, in the 25mm ID version.
http://www.pegasusautoracing.com/group.asp?GroupID...
it’s easy to see how you can easily add $100 in bearings per corner of the car especially when you factor in the hardened races and hardened thrust washers and extra machining.
I can jump online and order standard bearings easily and cheaply.
Was thinking of something like McMasterCarr part number 5972K82
ID12mm, OD28mm and Width 8mm single row sealed ball bearing as it’s easy to get, $5 Australian each at the local industrial supplies (a bit like an alternator bearing). They are also sealed and light, and would be easy to make an assembly to fit them. Keep in mind that this is going into an entry level small hill climb car, so something that results in $5000 per corner (once you include shipping) of the car in suspension bits and different bearings is going to break the budget.
The initial question related to what or how do you size these things?
what have other people used?
If you know the spring rate of the spring that would also be a good indication of the load as well i guess?
I think i’m getting closer to working out what would be an acceptable solution.
If I was doing it for the Ultima I would probably go with something like this, in the 25mm ID version.
http://www.pegasusautoracing.com/group.asp?GroupID...
it’s easy to see how you can easily add $100 in bearings per corner of the car especially when you factor in the hardened races and hardened thrust washers and extra machining.
Yes these are what people have used on similar design to my suspension (gtrclive etc)... I originally bought a job lot of motor bike wheel bearing which can more than take the load and are around £10 for 8 (I also use these on the boor hinges etc) however our rockers are only going to move in a small range of the bearing and so roller bearings will wear badly over time (due to the loads).... thats why mini wheel bearings are good as they are needle bearings and the right approx size.
I have not made mine but I bucked the trend and went down the local bearing specialist and purchased a needle bearing off the shelf thats around £5 and I will design my carriers around these.
If you think about loads, they wont be as much as the loads on a wheel bearing of similar weight car and thus using one should be more than adequate even for hard track use.
I have not made mine but I bucked the trend and went down the local bearing specialist and purchased a needle bearing off the shelf thats around £5 and I will design my carriers around these.
If you think about loads, they wont be as much as the loads on a wheel bearing of similar weight car and thus using one should be more than adequate even for hard track use.
Thanks to all. I looked up the mini wheel bearings and they do indeed look like a solution.
In referance to the side loading -
It's as straight as we can get it.
Kind regards Ryan
PS - dont fuss about the bump steer, the rack still needs to be extended on one side and placed offcentre to clear the middle pedal.
In referance to the side loading -
It's as straight as we can get it.
Kind regards Ryan
PS - dont fuss about the bump steer, the rack still needs to be extended on one side and placed offcentre to clear the middle pedal.
Slow M said:
Also, with everything else around the foot box triangulated, wouldn't you want a member directly in line with, and behind the rack?
yes, early stages, steering rack is only shown in that way so that we can get the frame design sorted so that all the tubes are in place to suport loads and insure that we have the required clerances. in this case the rack is show to determing if frankensitens feet will fit and to insure minimal bump steer.Ryan
Slow M said:
Would moving the weight down make sense if you're not looking for the aero advantage of an open wheel car? (sorry if I missed that part) 
Also sorry about Frankensteining your drawing, working w/ my left here.
B
It is to be an open wheeler hill climb car. entry level but must be as safe as posible. i think having the shocks up high will minimise the chances of something getting pushed into the foot well in the event that one of the drivers has an off.Also sorry about Frankensteining your drawing, working w/ my left here.
B
Im building it (one of 3 at this stage) with a group, so ill put your ideas to the pannel.
Ryan
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